Create Transaction

Create a transaction on Arweave

The createTransaction function creates a transaction based on the input parameters. The transaction can either be a data upload transaction or a wallet to wallet (token transfer) transaction.

Basic Syntax

The function is called as follows:

import { createTransaction } from 'arweavekit/transaction'

const transaction = await createTransaction({params});

Input Parameters

The following params are available for this function and they must be passed in as an object:

  • type: 'data' | 'wallet' : The type of transaction to be created. A data type transaction uploads data on Arweave whereas a wallet type transaction transfers tokens from one wallet to another.

  • key: JWKInterface (optional) : The private key for the wallet address to be fetched. The wallet key is optional for default transaction creation as no key is needed until signing a transaction, however, it must be passed in if the useBundlr or signAndPost option is set to true. The wallet key file can be loaded as follows:

import { readFileSync } from 'fs';

const key = JSON.parse(readFileSync('wallet.json').toString());

Private keys must be kept secure at all times. Please ensure that the wallet.json file is not pushed to a version control (eg. GitHub).

It is important to JSON.parse the read file as this returns the key in the correct format (object) for further use.

  • environment: 'local' | 'mainnet' : The environment for creating transactions. As this is only one part of the three step process of uploading transactions to Arweave, it is important that the transaction is signed and posted in the same environment it is created on.

An arlocal instance must be running on port 1984 for the function to work with the local environment. To create one, simply run npx arlocal in the command line. Learn more about arlocal here.

Currently, the Bundlr SDK only supports the mainnet environment.

  • target: string (optional) : The wallet address to which the wallet to wallet transaction must be sent.

The target must be accompanied with a quantity , else it sends a transaction with 0 tokens by default.

  • quantity: string (optional) : The quantity specifies the units of Winston to be sent in a wallet to wallet transaction.

The quantity must be accompanied with a target wallet address.

Winston is the smallest possible unit of AR, similar to a satoshi in Bitcoin, or wei in Ethereum.

1 AR = 1000000000000 Winston (12 zeros) and 1 Winston = 0.000000000001 AR.

  • data: string | Uint8Array | ArrayBuffer (optional) : To create a data type transaction, this optional parameter can be passed in. The data can be passed as a string, Uint8Array or an ArrayBuffer (as preferred by the network).

  • options : Additional options can be passed in as a JSON object.

    • tags: array (optional) : Tags can be added to any transaction for ease of indexing and querying. The syntax for adding tags is as follows:

      tags: [{ 'name': key_name, 'value': some_value},
              { 'name': key_name2, 'value': some_value2}]

      The name is the key for a given value that can be used for querying the transaction in the future. By default the library adds the 'ArweaveKit' : '1.5.1' tag on the backend to help identify the library and version used to deploy the function.

    • signAndPost: boolean (optional) : By default, the transaction process on Arweave has three steps to reduce the computation time, and provide convenience and customisation. However, by setting this option to true, the function signs and posts the transaction on chain in the same function call.

    • useBundlr: boolean (optional) : Creates the transaction using bundlr network. Only data type transactions can use this option. If the data size is under 100kB the transaction does not require any fees for processing through Bundlr.

Currently, the Bundlr SDK only supports data based transactions and only on the mainnet.

The option to signAndPost must be set to true for using Bundlr. Transactions using Bundlr will be signed and posted to the network by default as there is no support for signing and uploading Bundlr transactions in separate steps.

Web Transactions using Bundlr will fallback on Arweave in case of failure.

const transaction = await createTransaction({
    key: { KEY_OBJECT },
    type: 'wallet',
    quantity: '1000000',
    environment: 'mainnet',
    options: {
        tags: [{ 'name': 'key_name', 'value': 'some_value'}],

This call creates wallet type transaction on the mainnet and adds the tags that we have defined. This needs to be signed and posted in the consequent steps to successfully upload on Arweave.

Returned Data

The function call returns the following data depending on input parameters:

  • Default transaction (when useBundlr is false):

    • An object of type Transaction is returned by Arweave.

    • The data related key value pairs hold information when data prop is passed in.

    • The target and quantity fields have in formation for wallet-to-wallet transactions.

    • The signature key has no information until the transaction is signed.

    • The id of a transaction is only received after calling the postTransaction function (basically, when the transaction is posted on Arweave).

    • On selecting the signAndPost option the function returns a status object along with the transaction object. status: 200 and statusText: 'OK' indicates a successful post request on Arweave.

    • The transaction is created on the selected environment (local or mainnet).

  • When the useBundlr option is set to true:

    • An object of type Bundlr Transaction and an object containing the id of the posted transaction and the timestamp are returned.

    • The Bundlr Transaction object consists information regarding the network, currency, data to be posted, tags, etc.

    • The environment is always mainnet.

  • A few errors help identify the correct parameters in case any might be missing or not as expected.

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