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Recursive Length Prefix encoding for Node.js and the browser.


To obtain the latest version, simply require the project using npm:

npm install @ethereumjs/rlp

Install with -g if you want to use the CLI.


import assert from 'assert'
import { RLP } from '@ethereumjs/rlp'

const nestedList = [[], [[]], [[], [[]]]]
const encoded = RLP.encode(nestedList)
const decoded = RLP.decode(encoded)
assert.deepEqual(nestedList, decoded)


With the breaking release round in Summer 2023 we have added hybrid ESM/CJS builds for all our libraries (see section below) and have eliminated many of the caveats which had previously prevented a frictionless browser usage.

It is now easily possible to run a browser build of one of the EthereumJS libraries within a modern browser using the provided ESM build. For a setup example see ./examples/browser.html.


RLP.encode(plain) - RLP encodes an Array, Uint8Array or String and returns a Uint8Array.

RLP.decode(encoded, [stream=false]) - Decodes an RLP encoded Uint8Array, Array or String and returns a Uint8Array or NestedUint8Array. If stream is enabled, it will just decode the first rlp sequence in the Uint8Array. By default, it would throw an error if there are more bytes in Uint8Array than used by the rlp sequence.

Buffer compatibility

If you would like to continue using Buffers like in rlp v2, you can use:

import assert from 'assert'
import { arrToBufArr, bufArrToArr } from '@ethereumjs/util'
import { RLP } from '@ethereumjs/rlp'

const bufferList = [Buffer.from('123', 'hex'), Buffer.from('456', 'hex')]
const encoded = RLP.encode(bufArrToArr(bufferList))
const encodedAsBuffer = Buffer.from(encoded)
const decoded = RLP.decode(Uint8Array.from(encodedAsBuffer)) // or RLP.decode(encoded)
const decodedAsBuffers = arrToBufArr(decoded)
assert.deepEqual(bufferList, decodedAsBuffers)

Buffer -> Uint8Array

With the breaking releases from Summer 2023 we have removed all Node.js specific Buffer usages from our libraries and replace these with Uint8Array representations, which are available both in Node.js and the browser (Buffer is a subclass of Uint8Array).

We have converted existing Buffer conversion methods to Uint8Array conversion methods in the @ethereumjs/util bytes module, see the respective README section for guidance.

BigInt Support

Starting with v4 the usage of BN.js for big numbers has been removed from the library and replaced with the usage of the native JS BigInt data type (introduced in ES2020).

Please note that number-related API signatures have changed along with this version update and the minimal build target has been updated to ES2020.


rlp encode <JSON string>
rlp decode <0x-prefixed hex string>


  • rlp encode '5' -> 0x05
  • rlp encode '[5]' -> 0xc105
  • rlp encode '["cat", "dog"]' -> 0xc88363617483646f67
  • rlp decode 0xc88363617483646f67 -> ["cat","dog"]


See our organizational documentation for an introduction to EthereumJS as well as information on current standards and best practices. If you want to join for work or carry out improvements on the libraries, please review our contribution guidelines first.





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