diff --git a/API.md b/API.md
index 4735113..04e5452 100644
--- a/API.md
+++ b/API.md
@@ -29,17 +29,17 @@
 * dht.put
 * dht.query
 * dns
-* files.cp
+* [files.cp](#filescp)
 * files.flush
 * files.ls
 * files.lsPullStream
-* files.mkdir
+* [files.mkdir](#filesmkdir)
 * files.mv
 * files.read
 * files.readPullStream
 * files.rm
 * files.stat
-* files.write
+* [files.write](#fileswrite)
 * [id](#id) TODO: add docs
 * key.export
 * key.gen
@@ -176,6 +176,9 @@ Add/import files and directories to IPFS and retrieve their CID(s).
 * `options.hashAlg` (optional) - Hashing algorithm to use when creating the CID(s). [Available values]( https://github.com/multiformats/js-multihash/blob/master/src/constants.js#L5-L343).
     * Type: `String`
     * Default: `sha2-256`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
 * `options.onlyHash` (optional) - Do not add the file(s) to IPFS, only calculate the CID(s).
     * Type: `Boolean`
     * Default: `false`
@@ -185,6 +188,9 @@ Add/import files and directories to IPFS and retrieve their CID(s).
 * `options.progress` (optional) - A function that receives progress updates as data is added to IPFS. It is called with the byte length of chunks as a file is added to IPFS.
     * Type: `Function(bytes<Number>)`
     * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.quiet` (optional) - Return a minimal output.
     * Type: `Boolean`
     * Default: `false`
@@ -401,6 +407,12 @@ Fetch a raw block from the IPFS block store or the network via bitswap if not lo
 * `options` (optional)
     * Type: `Object`
     * Default: `null`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -434,6 +446,9 @@ Put a block into the IPFS block store.
 * `options.format` (optional) - Name of the IPLD format this block is encoded with
     * Type: `String`
     * Default: `dag-pb`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
 * `options.mhtype` (optional) - Name of the multihash hashing algorithm to use
     * Type: `String`
     * Default: `sha2-256`
@@ -443,6 +458,9 @@ Put a block into the IPFS block store.
 * `options.pin` (optional) - Pin this block so it is not garbage collected
     * Type: `Boolean`
     * Default: `false`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: {}
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -484,6 +502,12 @@ Get status for a block.
 * `options` (optional)
     * Type: `Object`
     * Default: `null`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -524,12 +548,18 @@ Read files from IPFS.
 * `options` (optional)
     * Type: `Object`
     * Default: `null`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
 * `options.offset` (optional) - Byte offset to start reading from
     * Type: `Number`
     * Default: `0`
 * `options.length` (optional) - Number of bytes to read
     * Type: `Number`
     * Default: `null` (read to the end of the file)
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -562,6 +592,186 @@ hello world!
 */
 ```
 
+## files.cp
+
+Copy files into [MFS](https://docs.ipfs.io/guides/concepts/mfs/).
+
+### `files.cp(...from, to, [options]): Promise`
+
+#### Parameters
+
+* `from` - Path(s) of the source to copy. It might be an existing MFS path to a file or a directory (e.g. `/my-dir/my-file.txt`) or an IPFS path (e.g. `/ipfs/QmWGeRAEgtsHW3ec7U4qW2CyVy7eA2mFRVbk1nb24jFyks`)
+    * Type: `String`
+* `to` - Path of the destination to copy to
+    * Type: `String`
+* `options` (optional)
+    * Type: `Object`
+    * Default: `null`
+* `options.flush` (optional) - Immediately flush MFS changes to disk
+    * Type: `Boolean`
+    * Default: `true`
+* `options.format` (optional) - Type of nodes to write any newly created directories as
+    * Type: `String`
+    * Default: `dag-pb`
+* `options.hashAlg` (optional) - Hashing algorithm to use when creating the CID(s). [Available values]( https://github.com/multiformats/js-multihash/blob/master/src/constants.js#L5-L343).
+    * Type: `String`
+    * Default: `sha2-256`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.parents` (optional) - Create parent directories if they do not exist
+    * Type: `Boolean`
+    * Default: `false`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
+* `options.signal` (optional) - A signal that can be used to abort the request
+    * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
+    * Default: `null`
+
+If `from` has multiple values then `to` must be a directory.
+
+If `from` has a single value and `to` exists and is a directory, `from` will be copied into `to`.
+
+If `from` has a single value and `to` exists and is a file, `from` must be a file and the contents of `to` will be replaced with the contents of `from` otherwise an error will be thrown.
+
+If `from` is an IPFS path, and an MFS path exists with the same name, the IPFS path will be chosen.
+
+#### Returns
+
+A promise that resolves when the operation is complete.
+
+* Type: `Promise`
+
+#### Examples
+
+```js
+// To copy a file
+await ipfs.files.cp('/src-file', '/dst-file')
+
+// To copy a directory
+await ipfs.files.cp('/src-dir', '/dst-dir')
+
+// To copy multiple files to a directory
+await ipfs.files.cp('/src-file1', '/src-file2', '/dst-dir')
+```
+
+## files.mkdir
+
+Make a directory in [MFS](https://docs.ipfs.io/guides/concepts/mfs/).
+
+### `files.mkdir(path, [options]): Promise`
+
+#### Parameters
+
+* `path` - path to the directory to make
+    * Type: `String`
+* `options` (optional)
+    * Type: `Object`
+    * Default: `null`
+* `options.cidVersion` (optional) - The CID version to use when storing the data (storage keys are based on the CID, including its version).
+    * Type: `Number` (0 or 1)
+    * Default: `0`
+* `options.flush` (optional) - Immediately flush MFS changes to disk
+    * Type: `Boolean`
+    * Default: `true`
+* `options.format` (optional) - Type of nodes to write any newly created directories as
+    * Type: `String`
+    * Default: `dag-pb`
+* `options.hashAlg` (optional) - Hashing algorithm to use when creating the CID(s). [Available values]( https://github.com/multiformats/js-multihash/blob/master/src/constants.js#L5-L343).
+    * Type: `String`
+    * Default: `sha2-256`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.parents` (optional) - Create parent directories if they do not exist
+    * Type: `Boolean`
+    * Default: `false`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
+* `options.signal` (optional) - A signal that can be used to abort the request
+    * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
+    * Default: `null`
+
+#### Returns
+
+A promise that resolves when the operation is complete.
+
+* Type: `Promise`
+
+#### Examples
+
+```js
+await ipfs.files.mkdir('/my/beautiful/directory')
+```
+
+## files.write
+
+Write to a file in [MFS](https://docs.ipfs.io/guides/concepts/mfs/).
+
+### `files.write(path, content, [options]): Promise`
+
+#### Parameters
+
+* `path` - Path to the file that should be written to
+    * Type: `String`
+* `content` - File content
+    * Type (one of):
+        * `Buffer`, or "buffer like": `ArrayBuffer`/`TypedArray`
+        * `Blob`/`File` (browser only)
+        * `Iterable<Number>` (e.g. array of bytes)
+        * `AsyncIterable<Buffer>` (e.g. a Node.js Stream)
+        * `PullStream<Buffer>`
+* `options` (optional)
+    * Type: `Object`
+    * Default: `null`
+* `options.cidVersion` (optional) - The CID version to use when storing the data (storage keys are based on the CID, including its version).
+    * Type: `Number` (0 or 1)
+    * Default: `0`
+* `options.count` (optional) - Number of bytes to write
+    * Type: `Number`
+    * Default: All bytes provided by `content`
+* `options.create` (optional) - Create file if it does not exist
+    * Type: `Boolean`
+    * Default: `false`
+* `options.hashAlg` (optional) - Hashing algorithm to use when creating the CID(s). [Available values]( https://github.com/multiformats/js-multihash/blob/master/src/constants.js#L5-L343).
+    * Type: `String`
+    * Default: `sha2-256`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.offset` (optional) - Byte offset to begin writing at
+    * Type: `Number`
+    * Default: `0`
+* `options.parents` (optional) - Create parent directories if they do not exist
+    * Type: `Boolean`
+    * Default: `false`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
+* `options.rawLeaves` (optional) - DAG leaf nodes contain raw file data and are not wrapped in a protobuf
+    * Type: `Boolean`
+    * Default: `false`
+* `options.signal` (optional) - A signal that can be used to abort the request
+    * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
+    * Default: `null`
+* `options.truncate` (optional) - Truncate the file to size zero before writing
+    * Type: `Boolean`
+    * Default: `false`
+
+#### Returns
+
+A promise that resolves when the operation is complete.
+
+* Type: `Promise`
+
+#### Examples
+
+```js
+await ipfs.files.write('/hello-world', Buffer.from('Hello, world!'))
+```
+
 ## pubsub.ls
 
 List subscribed topics by name.
@@ -573,6 +783,12 @@ List subscribed topics by name.
 * `options` (optional)
     * Type: `Object`
     * Default: `null`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -607,6 +823,12 @@ List peers we are currently pubsubbing with, optionally filtered by topic name.
 * `options` (optional)
     * Type: `Object`
     * Default: `null`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -642,6 +864,12 @@ Publish a message to a given pubsub topic.
 * `options` (optional)
     * Type: `Object`
     * Default: `null`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -686,9 +914,15 @@ Subscribe to messages on a given topic.
 * `options.discover` (optional) - Try to discover other peers subscribed to the same topic
     * Type: `Boolean`
     * Deafult: `false`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
 * `options.onError` (optional) - An error handler called when the request errors or parsing of a given message fails. It is passed two parameters, the error that occurred and a boolean indicating if it was a fatal error or not (fatal errors terminate the subscription).
     * Type: `Function(err<Error>, fatal<Boolean>)`
     * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -721,7 +955,7 @@ data: hi
 
 Stop receiving messages for a given topic.
 
-### `pubsub.unsubscribe(topic, [handler], [options]): Promise`
+### `pubsub.unsubscribe(topic, [handler]): Promise`
 
 #### Parameters
 
@@ -730,12 +964,6 @@ Stop receiving messages for a given topic.
 * `handler` (optional) - The handler function currently registered for this topic. If not provided, **all** handlers for the passed topic will be unsubscribed. Note this only works using the Promise API.
     * Type: `Function`
     * Default: `null`
-* `options` (optional)
-    * Type: `Object`
-    * Default: `null`
-* `options.signal` (optional) - A signal that can be used to abort the request
-    * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
-    * Default: `null`
 
 #### Returns
 
@@ -769,6 +997,12 @@ Open a connection to a given address.
 * `options` (optional)
     * Type: `Object`
     * Default: `null`
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
+    * Default: `null`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
 * `options.signal` (optional) - A signal that can be used to abort the request
     * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
     * Default: `null`
@@ -805,12 +1039,18 @@ List peers with open connections.
 * `options.direction` (optional) - Return direction information for each peer (inbound/outbound).
     * Type: `Boolean`
     * Default: `false`
-* `options.signal` (optional) - A signal that can be used to abort the request
-    * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
+* `options.headers` (optional) - Custom HTTP headers to send
+    * Type: `Object`
     * Default: `null`
 * `options.latency` (optional) - Return latency information for each peer.
     * Type: `Boolean`
     * Default: `false`
+* `options.qs` (optional) - Additional query string parameters
+    * Type: `Object`
+    * Default: `null`
+* `options.signal` (optional) - A signal that can be used to abort the request
+    * Type: [`AbortSignal`](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal)
+    * Default: `null`
 * `options.streams` (optional) - Return streams information for each peer.
     * Type: `Boolean`
     * Default: `false`
diff --git a/README.md b/README.md
index 90d2cb6..19e9350 100644
--- a/README.md
+++ b/README.md
@@ -166,17 +166,17 @@ This module is in heavy development, not all API methods are available (or docum
 * dht.put
 * dht.query
 * dns
-* files.cp
+* [files.cp](./API.md#filescp)
 * files.flush
 * files.ls
 * files.lsPullStream
-* files.mkdir
+* [files.mkdir](./API.md#filesmkdir)
 * files.mv
 * files.read
 * files.readPullStream
 * files.rm
 * files.stat
-* files.write
+* [files.write](./API.md#fileswrite)
 * [id](./API.md#id) TODO: add docs
 * key.export
 * key.gen
diff --git a/package.json b/package.json
index 2bb2ca2..8af4b04 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,8 @@
   "main": "src/index.js",
   "browser": {
     "./src/lib/configure.js": "./src/lib/configure.browser.js",
-    "./src/add/form-data.js": "./src/add/form-data.browser.js"
+    "./src/add/form-data.js": "./src/add/form-data.browser.js",
+    "./src/files/write/form-data.js": "./src/files/write/form-data.browser.js"
   },
   "browserslist": ">1.5% or node >=10 and not ios_saf <13 and not ie 11 and not dead",
   "files": [
@@ -42,7 +43,7 @@
     "bignumber.js": "^9.0.0",
     "chai": "^4.2.0",
     "dirty-chai": "^2.0.1",
-    "go-ipfs-dep": "~0.4.21",
+    "go-ipfs-dep": "^0.4.21",
     "interface-ipfs-core": "~0.105.1",
     "ipfs-block": "^0.8.1",
     "ipfsd-ctl": "^0.43.0",
diff --git a/src/add/form-data.browser.js b/src/add/form-data.browser.js
index 5ea6054..46f0254 100644
--- a/src/add/form-data.browser.js
+++ b/src/add/form-data.browser.js
@@ -3,7 +3,7 @@
 
 const normaliseInput = require('./normalise-input')
 
-exports.toFormData = async function toFormData (input) {
+exports.toFormData = async (input) => {
   const files = normaliseInput(input)
   const formData = new FormData()
   let i = 0
diff --git a/src/add/form-data.js b/src/add/form-data.js
index 90dc0e1..ce82fbe 100644
--- a/src/add/form-data.js
+++ b/src/add/form-data.js
@@ -1,11 +1,10 @@
 'use strict'
 
-// const toStream = require('async-iterator-to-stream')
 const FormData = require('form-data')
-const { Readable } = require('stream')
 const normaliseInput = require('./normalise-input')
+const toStream = require('../lib/iterable-to-readable-stream')
 
-exports.toFormData = async function toFormData (input) {
+exports.toFormData = async (input) => {
   // In Node.js, FormData can be passed a stream so no need to buffer
   const files = normaliseInput(input)
   const formData = new FormData()
@@ -40,26 +39,3 @@ exports.toFormData = async function toFormData (input) {
 
   return formData
 }
-
-function toStream (iterable) {
-  let reading = false
-  return new Readable({
-    async read (size) {
-      if (reading) return
-      reading = true
-
-      try {
-        while (true) {
-          const { value, done } = await iterable.next(size)
-          if (done) return this.push(null)
-          if (!this.push(value)) break
-        }
-      } catch (err) {
-        this.emit('error', err)
-        if (iterable.return) iterable.return()
-      } finally {
-        reading = false
-      }
-    }
-  })
-}
diff --git a/src/add/index.js b/src/add/index.js
index 76c3f6e..2bf59ec 100644
--- a/src/add/index.js
+++ b/src/add/index.js
@@ -27,7 +27,8 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
       'shard-split-threshold': options.shardSplitThreshold,
       silent: options.silent,
       trickle: options.trickle,
-      'wrap-with-directory': options.wrapWithDirectory
+      'wrap-with-directory': options.wrapWithDirectory,
+      ...(options.qs || {})
     })
 
     const url = `${apiUrl}${apiPath}/add${qs}`
diff --git a/src/add/normalise-input.js b/src/add/normalise-input.js
index 3750fcc..b11e07d 100644
--- a/src/add/normalise-input.js
+++ b/src/add/normalise-input.js
@@ -1,9 +1,8 @@
 'use strict'
 /* eslint-env browser */
 
-const toIterator = require('pull-stream-to-async-iterator')
 const { Buffer } = require('buffer')
-const blobToAsyncIterable = require('../lib/blob-to-async-iterable')
+const toAsyncIterable = require('../lib/file-data-to-async-iterable')
 
 /*
 Transform one of:
@@ -126,38 +125,3 @@ module.exports = function normalizeInput (input) {
 function normalizeTuple ({ path, content }) {
   return { path: path || '', content: content ? toAsyncIterable(content) : null }
 }
-
-function toAsyncIterable (input) {
-  // Buffer|ArrayBuffer|TypedArray|array of bytes
-  if (input[Symbol.iterator]) {
-    const buf = Buffer.from(input)
-    return Object.assign(
-      (async function * () { yield buf })(), // eslint-disable-line require-await
-      { length: buf.length }
-    )
-  }
-
-  // Blob|File
-  if (typeof Blob !== 'undefined' && input instanceof Blob) {
-    return Object.assign(
-      blobToAsyncIterable(input),
-      { length: input.size }
-    )
-  }
-
-  // AsyncIterable<Buffer>
-  if (input[Symbol.asyncIterator]) {
-    return (async function * () {
-      for await (const chunk of input) {
-        yield Buffer.from(chunk)
-      }
-    })()
-  }
-
-  // PullStream
-  if (typeof input === 'function') {
-    return toIterator(input)
-  }
-
-  throw new Error('Unexpected input: ' + typeof input)
-}
diff --git a/src/bitswap/stat.js b/src/bitswap/stat.js
index 1da189f..1b10c35 100644
--- a/src/bitswap/stat.js
+++ b/src/bitswap/stat.js
@@ -2,13 +2,15 @@
 
 const configure = require('../lib/configure')
 const { ok } = require('../lib/fetch')
+const { objectToQuery } = require('../lib/querystring')
 const toCamel = require('../lib/to-camel')
 
 module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return async (options) => {
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/bitswap/stat`
+    const qs = objectToQuery(options.qs)
+    const url = `${apiUrl}${apiPath}/bitswap/stat${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/bitswap/wantlist.js b/src/bitswap/wantlist.js
index 21ee8ac..8d31b01 100644
--- a/src/bitswap/wantlist.js
+++ b/src/bitswap/wantlist.js
@@ -13,7 +13,12 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
 
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/bitswap/wantlist${objectToQuery({ peer: peerId })}`
+    const qs = objectToQuery({
+      peer: peerId,
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/bitswap/wantlist${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/block/get.js b/src/block/get.js
index de4ceeb..83e0204 100644
--- a/src/block/get.js
+++ b/src/block/get.js
@@ -3,12 +3,18 @@
 const { Buffer } = require('buffer')
 const configure = require('../lib/configure')
 const { ok } = require('../lib/fetch')
+const { objectToQuery } = require('../lib/querystring')
 
 module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return async (cid, options) => {
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/block/get?arg=${encodeURIComponent(cid)}`
+    const qs = objectToQuery({
+      arg: cid.toString(),
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/block/get${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/block/put.js b/src/block/put.js
index 2698396..66014c8 100644
--- a/src/block/put.js
+++ b/src/block/put.js
@@ -14,7 +14,8 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
       format: options.format,
       mhtype: options.mhtype,
       mhlen: options.mhlen,
-      pin: options.pin
+      pin: options.pin,
+      ...(options.qs || {})
     })
 
     const url = `${apiUrl}${apiPath}/block/put${qs}`
diff --git a/src/block/stat.js b/src/block/stat.js
index a9d0a24..b47162e 100644
--- a/src/block/stat.js
+++ b/src/block/stat.js
@@ -1,6 +1,7 @@
 'use strict'
 
 const configure = require('../lib/configure')
+const { objectToQuery } = require('../lib/querystring')
 const { ok } = require('../lib/fetch')
 const toCamel = require('../lib/to-camel')
 
@@ -8,7 +9,12 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return async (cid, options) => {
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/block/stat?arg=${encodeURIComponent(cid)}`
+    const qs = objectToQuery({
+      arg: cid.toString(),
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/block/stat${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/cat.js b/src/cat.js
index 4c17f45..90519d4 100644
--- a/src/cat.js
+++ b/src/cat.js
@@ -3,12 +3,18 @@
 const { Buffer } = require('buffer')
 const configure = require('./lib/configure')
 const { ok, toIterable } = require('./lib/fetch')
+const { objectToQuery } = require('./lib/querystring')
 
 module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return (cid, options) => (async function * () {
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/cat?arg=${encodeURIComponent(cid)}`
+    const qs = objectToQuery({
+      arg: cid.toString(),
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/cat${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/files/cp.js b/src/files/cp.js
new file mode 100644
index 0000000..08baedc
--- /dev/null
+++ b/src/files/cp.js
@@ -0,0 +1,32 @@
+'use strict'
+
+const configure = require('../lib/configure')
+const { ok } = require('../lib/fetch')
+const { objectToQuery } = require('../lib/querystring')
+
+module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
+  return async (...args) => {
+    let options = {}
+
+    if (typeof args[args.length - 1] === 'object') {
+      options = args.pop()
+    }
+
+    const qs = objectToQuery({
+      arg: args,
+      flush: options.flush,
+      format: options.format,
+      hash: options.hashAlg,
+      parents: options.parents,
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/files/cp${qs}`
+    const res = await ok(fetch(url, {
+      signal: options.signal,
+      headers: options.headers || headers
+    }))
+
+    return res.text()
+  }
+})
diff --git a/src/files/mkdir.js b/src/files/mkdir.js
new file mode 100644
index 0000000..fb01ad1
--- /dev/null
+++ b/src/files/mkdir.js
@@ -0,0 +1,29 @@
+'use strict'
+
+const configure = require('../lib/configure')
+const { ok } = require('../lib/fetch')
+const { objectToQuery } = require('../lib/querystring')
+
+module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
+  return async (path, options) => {
+    options = options || {}
+
+    const qs = objectToQuery({
+      arg: path,
+      'cid-version': options.cidVersion,
+      flush: options.flush,
+      format: options.format,
+      hash: options.hashAlg,
+      parents: options.parents,
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/files/mkdir${qs}`
+    const res = await ok(fetch(url, {
+      signal: options.signal,
+      headers: options.headers || headers
+    }))
+
+    return res.text()
+  }
+})
diff --git a/src/files/write/form-data.browser.js b/src/files/write/form-data.browser.js
new file mode 100644
index 0000000..f2ec032
--- /dev/null
+++ b/src/files/write/form-data.browser.js
@@ -0,0 +1,21 @@
+'use strict'
+/* eslint-env browser */
+
+const toAsyncIterable = require('../../lib/file-data-to-async-iterable')
+
+exports.toFormData = async (path, input) => {
+  input = toAsyncIterable(input)
+  const formData = new FormData()
+
+  // In the browser there's _currently_ no streaming upload, buffer up our
+  // async iterator chunks and append a big Blob :(
+  // One day, this will be browser streams
+  const bufs = []
+  for await (const chunk of input) {
+    bufs.push(Buffer.isBuffer(chunk) ? chunk.buffer : chunk)
+  }
+
+  formData.append('file', new Blob(bufs, { type: 'application/octet-stream' }))
+
+  return formData
+}
diff --git a/src/files/write/form-data.js b/src/files/write/form-data.js
new file mode 100644
index 0000000..2a486d9
--- /dev/null
+++ b/src/files/write/form-data.js
@@ -0,0 +1,24 @@
+'use strict'
+
+const FormData = require('form-data')
+const toAsyncIterable = require('../../lib/file-data-to-async-iterable')
+const toStream = require('../../lib/iterable-to-readable-stream')
+
+exports.toFormData = (path, input) => {
+  input = toAsyncIterable(input)
+  const formData = new FormData()
+
+  formData.append(
+    'file',
+    // FIXME: add a `path` property to the stream so `form-data` doesn't set
+    // a Content-Length header that is only the sum of the size of the
+    // header/footer when knownLength option (below) is null.
+    Object.assign(toStream(input), { path }),
+    {
+      contentType: 'application/octet-stream',
+      knownLength: input.length // Send Content-Length header if known
+    }
+  )
+
+  return formData
+}
diff --git a/src/files/write/index.js b/src/files/write/index.js
new file mode 100644
index 0000000..2901706
--- /dev/null
+++ b/src/files/write/index.js
@@ -0,0 +1,36 @@
+'use strict'
+
+const { objectToQuery } = require('../../lib/querystring')
+const configure = require('../../lib/configure')
+const { ok } = require('../../lib/fetch')
+const { toFormData } = require('./form-data')
+
+module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
+  return async (path, input, options) => {
+    options = options || {}
+
+    const qs = objectToQuery({
+      arg: path,
+      'stream-channels': true,
+      'cid-version': options.cidVersion,
+      count: options.count,
+      create: options.create,
+      hash: options.hashAlg,
+      offset: options.offset,
+      parents: options.parents,
+      'raw-leaves': options.rawLeaves,
+      truncate: options.truncate,
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/files/write${qs}`
+    const res = await ok(fetch(url, {
+      method: 'POST',
+      signal: options.signal,
+      headers: options.headers || headers,
+      body: await toFormData(path, input)
+    }))
+
+    return res.text()
+  }
+})
diff --git a/src/id.js b/src/id.js
index fa3a3e4..a14e7e8 100644
--- a/src/id.js
+++ b/src/id.js
@@ -2,12 +2,14 @@
 
 const configure = require('./lib/configure')
 const { ok } = require('./lib/fetch')
+const { objectToQuery } = require('./lib/querystring')
 const toCamel = require('./lib/to-camel')
 
 module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return async options => {
     options = options || {}
-    const url = `${apiUrl}${apiPath}/id`
+    const qs = objectToQuery(options.qs)
+    const url = `${apiUrl}${apiPath}/id${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/index.js b/src/index.js
index 5ab5aff..a747f5e 100644
--- a/src/index.js
+++ b/src/index.js
@@ -25,6 +25,11 @@ module.exports = config => {
     },
     cat: callbackify(concatify(cat)),
     catPullStream: pullify.source(cat),
+    files: {
+      cp: callbackify(require('./files/cp')(config)),
+      mkdir: callbackify(require('./files/mkdir')(config)),
+      write: callbackify(require('./files/write')(config))
+    },
     ls: callbackify(collectify(ls)),
     lsPullStream: pullify.source(ls),
     id: callbackify(require('./id')(config)),
diff --git a/src/lib/file-data-to-async-iterable.js b/src/lib/file-data-to-async-iterable.js
new file mode 100644
index 0000000..ffa0f8d
--- /dev/null
+++ b/src/lib/file-data-to-async-iterable.js
@@ -0,0 +1,54 @@
+'use strict'
+/* eslint-env browser */
+
+const toIterator = require('pull-stream-to-async-iterator')
+const { Buffer } = require('buffer')
+const blobToAsyncIterable = require('../lib/blob-to-async-iterable')
+
+/*
+Transform one of:
+
+Buffer|ArrayBuffer|TypedArray
+Blob|File
+Iterable<Number>
+AsyncIterable<Buffer>
+PullStream<Buffer>
+
+Into:
+
+AsyncIterable<Buffer>
+*/
+module.exports = function toAsyncIterable (input) {
+  // Buffer|ArrayBuffer|TypedArray|array of bytes
+  if (input[Symbol.iterator]) {
+    const buf = Buffer.from(input)
+    return Object.assign(
+      (async function * () { yield buf })(), // eslint-disable-line require-await
+      { length: buf.length }
+    )
+  }
+
+  // Blob|File
+  if (typeof Blob !== 'undefined' && input instanceof Blob) {
+    return Object.assign(
+      blobToAsyncIterable(input),
+      { length: input.size }
+    )
+  }
+
+  // AsyncIterable<Buffer>
+  if (input[Symbol.asyncIterator]) {
+    return (async function * () {
+      for await (const chunk of input) {
+        yield Buffer.from(chunk)
+      }
+    })()
+  }
+
+  // PullStream
+  if (typeof input === 'function') {
+    return toIterator(input)
+  }
+
+  throw new Error('Unexpected input: ' + typeof input)
+}
diff --git a/src/lib/form-data.browser.js b/src/lib/form-data.browser.js
deleted file mode 100644
index 8b60885..0000000
--- a/src/lib/form-data.browser.js
+++ /dev/null
@@ -1,25 +0,0 @@
-'use strict'
-/* eslint-env browser */
-
-const isBuffer = require('is-buffer')
-
-exports.toFormData = async function toFormData (input) {
-  // If not an async iterator, this must conform to whatever FormData allows
-  if (!input[Symbol.asyncIterator]) {
-    const formData = new FormData()
-    formData.append('file', input)
-    return formData
-  }
-
-  // In the browser there's _currently_ no streaming upload, buffer up our
-  // async iterator chunks and append a big Blob :(
-
-  // One day, this will be browser streams
-  const formData = new FormData()
-  const bufs = []
-  for await (const chunk of input) {
-    bufs.push(isBuffer(chunk) ? chunk.buffer : chunk)
-  }
-  formData.append('file', new Blob(bufs))
-  return formData
-}
diff --git a/src/lib/form-data.js b/src/lib/form-data.js
deleted file mode 100644
index ca3926b..0000000
--- a/src/lib/form-data.js
+++ /dev/null
@@ -1,25 +0,0 @@
-'use strict'
-
-// const toStream = require('async-iterator-to-stream')
-const FormData = require('form-data')
-
-exports.toFormData = async function toFormData (input) {
-  // If not an async iterator, this must conform to whatever FormData allows
-  if (!input[Symbol.asyncIterator]) {
-    const formData = new FormData()
-    formData.append('file', input)
-    return formData
-  }
-
-  // In Node.js, FormData can be passed a stream so no need to buffer
-  const formData = new FormData()
-  const bufs = []
-  for await (const chunk of input) {
-    bufs.push(Buffer.from(chunk))
-  }
-  // FIXME: the below does not work! It should do, but only the first chunk
-  // gets uploaded :(
-  // formData.append('file', toStream(input))
-  formData.append('file', Buffer.concat(bufs))
-  return formData
-}
diff --git a/src/lib/iterable-to-readable-stream.js b/src/lib/iterable-to-readable-stream.js
new file mode 100644
index 0000000..f13d96d
--- /dev/null
+++ b/src/lib/iterable-to-readable-stream.js
@@ -0,0 +1,26 @@
+'use strict'
+
+const { Readable } = require('stream')
+
+module.exports = function toStream (iterable) {
+  let reading = false
+  return new Readable({
+    async read (size) {
+      if (reading) return
+      reading = true
+
+      try {
+        while (true) {
+          const { value, done } = await iterable.next(size)
+          if (done) return this.push(null)
+          if (!this.push(value)) break
+        }
+      } catch (err) {
+        this.emit('error', err)
+        if (iterable.return) iterable.return()
+      } finally {
+        reading = false
+      }
+    }
+  })
+}
diff --git a/src/lib/querystring.js b/src/lib/querystring.js
index e0ffc9a..df35b0a 100644
--- a/src/lib/querystring.js
+++ b/src/lib/querystring.js
@@ -5,6 +5,8 @@ const QueryString = require('querystring')
 // Convert an object to a query string INCLUDING leading ?
 // Excludes null/undefined values
 exports.objectToQuery = obj => {
+  if (!obj) return ''
+
   const qs = Object.entries(obj).reduce((obj, [key, value]) => {
     if (value != null) obj[key] = value
     return obj
diff --git a/src/ls.js b/src/ls.js
index d3107ef..7aa838e 100644
--- a/src/ls.js
+++ b/src/ls.js
@@ -9,7 +9,12 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return (path, options) => (async function * () {
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/ls${objectToQuery({ arg: path.toString() })}`
+    const qs = objectToQuery({
+      arg: path.toString(),
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/ls${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/ping.js b/src/ping.js
index 442b6d0..da96cf9 100644
--- a/src/ping.js
+++ b/src/ping.js
@@ -10,7 +10,12 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return (peerId, options) => (async function * () {
     options = options || {}
 
-    const qs = objectToQuery({ arg: peerId, count: options.count })
+    const qs = objectToQuery({
+      arg: peerId,
+      count: options.count,
+      ...(options.qs || {})
+    })
+
     const url = `${apiUrl}${apiPath}/ping${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
diff --git a/src/pubsub/ls.js b/src/pubsub/ls.js
index c65c17e..1bcec4f 100644
--- a/src/pubsub/ls.js
+++ b/src/pubsub/ls.js
@@ -2,12 +2,14 @@
 
 const configure = require('../lib/configure')
 const { ok } = require('../lib/fetch')
+const { objectToQuery } = require('../lib/querystring')
 
 module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return async (options) => {
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/pubsub/ls`
+    const qs = objectToQuery(options.qs)
+    const url = `${apiUrl}${apiPath}/pubsub/ls${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/pubsub/peers.js b/src/pubsub/peers.js
index f738677..5ef202a 100644
--- a/src/pubsub/peers.js
+++ b/src/pubsub/peers.js
@@ -13,7 +13,12 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
 
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/pubsub/peers${objectToQuery({ arg: topic })}`
+    const qs = objectToQuery({
+      arg: topic,
+      ...(options.qs || {})
+    })
+
+    const url = `${apiUrl}${apiPath}/pubsub/peers${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/src/pubsub/publish.js b/src/pubsub/publish.js
index 702f432..78d6f2b 100644
--- a/src/pubsub/publish.js
+++ b/src/pubsub/publish.js
@@ -2,13 +2,17 @@
 
 const { Buffer } = require('buffer')
 const configure = require('../lib/configure')
+const { objectToQuery } = require('../lib/querystring')
 const { ok } = require('../lib/fetch')
 
 module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return async (topic, data, options) => {
     options = options || {}
 
-    const url = `${apiUrl}${apiPath}/pubsub/pub?arg=${encodeURIComponent(topic)}&arg=${encodeBuffer(Buffer.from(data))}`
+    let qs = objectToQuery(options.qs)
+    qs = qs ? `&${qs.slice(1)}` : qs
+
+    const url = `${apiUrl}${apiPath}/pubsub/pub?arg=${encodeURIComponent(topic)}&arg=${encodeBuffer(Buffer.from(data))}${qs}`
     const res = await ok(fetch(url, {
       method: 'POST',
       signal: options.signal,
diff --git a/src/pubsub/subscribe.js b/src/pubsub/subscribe.js
index 2dbe545..5023292 100644
--- a/src/pubsub/subscribe.js
+++ b/src/pubsub/subscribe.js
@@ -14,7 +14,12 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
     options = options || {}
     options.signal = subsTracker.subscribe(topic, handler, options.signal)
 
-    const qs = objectToQuery({ arg: topic, discover: options.discover })
+    const qs = objectToQuery({
+      arg: topic,
+      discover: options.discover,
+      ...(options.qs || {})
+    })
+
     const url = `${apiUrl}${apiPath}/pubsub/sub${qs}`
     let res
 
diff --git a/src/swarm/connect.js b/src/swarm/connect.js
index 82cab96..401a253 100644
--- a/src/swarm/connect.js
+++ b/src/swarm/connect.js
@@ -9,7 +9,11 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
     addrs = Array.isArray(addrs) ? addrs : [addrs]
     options = options || {}
 
-    const qs = objectToQuery({ arg: addrs.map(a => a.toString()) })
+    const qs = objectToQuery({
+      arg: addrs.map(a => a.toString()),
+      ...(options.qs || {})
+    })
+
     const url = `${apiUrl}${apiPath}/swarm/connect${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
diff --git a/src/swarm/peers.js b/src/swarm/peers.js
index e9b706b..5db68c0 100644
--- a/src/swarm/peers.js
+++ b/src/swarm/peers.js
@@ -12,7 +12,8 @@ module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
     const qs = objectToQuery({
       verbose: options.verbose,
       streams: options.streams,
-      latency: options.latency
+      latency: options.latency,
+      ...(options.qs || {})
     })
 
     const url = `${apiUrl}${apiPath}/swarm/peers${qs}`
diff --git a/src/version.js b/src/version.js
index 934ac60..782c4e4 100644
--- a/src/version.js
+++ b/src/version.js
@@ -2,12 +2,14 @@
 
 const configure = require('./lib/configure')
 const { ok } = require('./lib/fetch')
+const { objectToQuery } = require('./lib/querystring')
 const toCamel = require('./lib/to-camel')
 
 module.exports = configure(({ fetch, apiUrl, apiPath, headers }) => {
   return async options => {
     options = options || {}
-    const url = `${apiUrl}${apiPath}/version`
+    const qs = objectToQuery(options.qs)
+    const url = `${apiUrl}${apiPath}/version${qs}`
     const res = await ok(fetch(url, {
       signal: options.signal,
       headers: options.headers || headers
diff --git a/test/interface.spec.js b/test/interface.spec.js
index 0dde420..63f72b1 100644
--- a/test/interface.spec.js
+++ b/test/interface.spec.js
@@ -264,7 +264,52 @@ describe('interface-ipfs-core tests', () => {
     ]
   })
 
-  tests.filesMFS(defaultCommon, { skip: { reason: 'LITE: not implemented yet' } })
+  tests.filesMFS(defaultCommon, {
+    skip: [{
+      name: 'write',
+      reason: 'LITE: depends on stat, stat not implemented yet'
+    },
+    {
+      name: 'stat',
+      reason: 'LITE: not implemented yet'
+    },
+    {
+      name: 'mv',
+      reason: 'LITE: not implemented yet'
+    },
+    {
+      name: 'rm',
+      reason: 'LITE: not implemented yet'
+    },
+    {
+      name: 'read',
+      reason: 'LITE: not implemented yet'
+    },
+    {
+      name: 'readReadableStream',
+      reason: 'LITE: Node.js streams not supported'
+    },
+    {
+      name: 'readPullStream',
+      reason: 'LITE: not implemented yet'
+    },
+    {
+      name: 'ls',
+      reason: 'LITE: not implemented yet'
+    },
+    {
+      name: 'lsReadableStream',
+      reason: 'LITE: Node.js streams not supported'
+    },
+    {
+      name: 'lsPullStream',
+      reason: 'LITE: not implemented yet'
+    },
+    {
+      name: 'flush',
+      reason: 'LITE: not implemented yet'
+    }]
+  })
 
   tests.key(defaultCommon, {
     // skip: [
diff --git a/test/utils/core-adapter/files/args-to-srcs.js b/test/utils/core-adapter/files/args-to-srcs.js
new file mode 100644
index 0000000..f720e06
--- /dev/null
+++ b/test/utils/core-adapter/files/args-to-srcs.js
@@ -0,0 +1,20 @@
+'use strict'
+
+module.exports = args => {
+  let options = {}
+  let sources = []
+
+  if (!Array.isArray(args[args.length - 1]) && typeof args[args.length - 1] === 'object') {
+    options = args.pop()
+  }
+
+  if (args.length === 1 && Array.isArray(args[0])) {
+    // support ipfs.files.cp([src, dest], opts)
+    sources = args[0]
+  } else {
+    // support ipfs.files.cp(src, dest, opts) and ipfs.files.cp(src1, src2, dest, opts)
+    sources = args
+  }
+
+  return { sources, options }
+}
diff --git a/test/utils/core-adapter/files/cp.js b/test/utils/core-adapter/files/cp.js
new file mode 100644
index 0000000..6ddd7be
--- /dev/null
+++ b/test/utils/core-adapter/files/cp.js
@@ -0,0 +1,8 @@
+'use strict'
+
+const toSources = require('./args-to-srcs')
+
+module.exports = ipfsLite => (...args) => {
+  const { sources, options } = toSources(args)
+  return ipfsLite.files.cp(...sources, options)
+}
diff --git a/test/utils/core-adapter/files/mkdir.js b/test/utils/core-adapter/files/mkdir.js
new file mode 100644
index 0000000..2b15197
--- /dev/null
+++ b/test/utils/core-adapter/files/mkdir.js
@@ -0,0 +1,12 @@
+'use strict'
+
+module.exports = ipfsLite => (path, options) => {
+  options = options || {}
+
+  if (options.p != null) {
+    options.parents = options.p
+    delete options.p
+  }
+
+  return ipfsLite.files.mkdir(path, options)
+}
diff --git a/test/utils/core-adapter/index.js b/test/utils/core-adapter/index.js
index bb8e67c..3589b9c 100644
--- a/test/utils/core-adapter/index.js
+++ b/test/utils/core-adapter/index.js
@@ -17,6 +17,11 @@ module.exports = ipfsLite => {
       put: callbackify(require('./block/put')(ipfsLite)),
       stat: ipfsLite.block.stat
     },
+    files: {
+      cp: callbackify(require('./files/cp')(ipfsLite)),
+      mkdir: callbackify(require('./files/mkdir')(ipfsLite)),
+      write: ipfsLite.files.write
+    },
     ls: callbackify(require('./ls')(ipfsLite)),
     lsPullStream: require('./ls-pull-stream')(ipfsLite),
     pubsub: {