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Blockchain API

Prepare Transactions

Build the transaction, keep the keys. Send a sender, a recipient and an amount; Crypto APIs returns the unsigned transaction with the fee, nonce or inputs worked out, ready to sign on your own server and broadcast.

Start free trial Read the docs
Unsigned: you sign Coins, tokens and NFTs Fees and nonces filled in
What you can build

Unsigned transactions for non-custodial wallets and payouts

Send coins

Prepare a native coin transfer on EVM, UTXO, XRP, Solana, Tezos and Kaspa chains, without running a node to pick the inputs or the nonce.

Send tokens and NFTs

Prepare fungible and non-fungible token transfers on EVM chains and Tron, SPL tokens on Solana, and FA1.2 and FA2 tokens on Tezos.

Sign where your keys live

Sign the prepared transaction with the free offline signer on your own server. Your private keys never reach Crypto APIs.

Quick start

Make your first Prepare Transactions call

Real paths and example responses from the API reference. Add your API key and run it.

  • Base URL https://rest.cryptoapis.io
  • Auth: the X-API-Key header
  • JSON responses, same shape on every chain
curl -X POST https://rest.cryptoapis.io/prepare-transactions/evm/ethereum/mainnet/native-coins \
  -H "Content-Type: application/json" \
  -H "X-API-Key: YOUR_API_KEY" \
  -d '{
  "data": {
    "item": {
      "additionalData": "yourAdditionalStriingHere",
      "amount": "2000000009340",
      "nonce": "0",
      "recipient": "0x0902a667d6a3f287835e0a4593cae4167384abc6",
      "sender": "0x1d107b75353229768dff96051262ce0088a3e26b"
    }
  }
}'
200 OKExample response, excerpt
{
  "fee": {
    "gasPrice": 47125353,
    "maxFeePerGas": 47125353,
    "maxPriorityFeePerGas": 47125353,
    "unit": "WEI"
  },
  "inputData": "0x006e0065006b006100760073007400720069006e0067",
  "nonce": 0,
  "recipient": "0x041c594a0cc194e826bef5411b29c7f27001b7e3"
}
Endpoints

Every Prepare Transactions endpoint

Each operation links to its page in the API reference, with its parameters and responses. Paths take the blockchain and the network, so moving to another chain is a change of path.

API reference
What it does
Method and path
Blockchains
Reference
Prepare A Fungible Token Transfer From Address EVM
POST/prepare-transactions/evm/{blockchain}/{network}/fungible-tokens
8 blockchains
Prepare Transaction From Address EVM
POST/prepare-transactions/evm/{blockchain}/{network}/native-coins
8 blockchains
Prepare A Non Fungible Token Transfer From Address EVM
POST/prepare-transactions/evm/{blockchain}/{network}/non-fungible-tokens
7 blockchains
Prepare A Native Coin Transfer From Address Tron
POST/prepare-transactions/evm/tron/{network}/native-coins
Tron
Prepare A Non Fungible Token Transfer From Address Tron
POST/prepare-transactions/evm/tron/{network}/non-fungible-tokens
Tron
Prepare A TRC-20 Token Transfer From Address Tron
POST/prepare-transactions/evm/tron/{network}/trc20-tokens
Tron
Prepare Transaction From Address UTXO
POST/prepare-transactions/utxo/{blockchain}/{network}/native-coins
6 blockchains
Prepare Transaction From Address XRP
POST/prepare-transactions/xrp/{network}/native-coins
XRP Ledger
Prepare A Native Coin Transfer From Address Solana
POST/prepare-transactions/solana/{network}/native-coins
Solana
Prepare An SPL Token Transfer From Address Solana
POST/prepare-transactions/solana/{network}/spl-tokens
Solana
Prepare An FA1.2 Token Transfer From Address Tezos
POST/prepare-transactions/tezos/{network}/fa1-2-tokens
Tezos
Prepare An FA2 Token Transfer From Address Tezos
POST/prepare-transactions/tezos/{network}/fa2-tokens
Tezos
Prepare A Native Coin Transfer From Address Tezos
POST/prepare-transactions/tezos/{network}/native-coins
Tezos
Prepare Kaspa Transaction
POST/prepare-transactions/kaspa/{network}/native-coins
Kaspa
Blockchains

Prepare Transactions works on 19 blockchains

Mainnets, and test networks where the chain has one. Open a chain for its own endpoints and quick start.

See all networks
Bitcoin Ethereum XRP Ledger Ethereum Classic Bitcoin Cash Dash Litecoin Dogecoin Zcash BNB Smart Chain Polygon Tron Solana Tezos Avalanche Arbitrum Optimism Base Kaspa
Pairs well with

Build the rest of the flow

All Blockchain API features
Offline SignerSign on your own server, free and open source Broadcast TransactionsSend a transaction you signed yourself Blockchain FeesFee recommendations and gas estimates
FAQ

Prepare Transactions questions

Which blockchains does Prepare Transactions support?

Prepare Transactions works on 19 blockchains: Bitcoin, Ethereum, XRP Ledger, Ethereum Classic, Bitcoin Cash, Dash, Litecoin, Dogecoin, Zcash, BNB Smart Chain, Polygon, Tron, Solana, Tezos, Avalanche, Arbitrum, Optimism, Base, Kaspa. Each chain's page lists its networks and its own endpoints.

Can I try Prepare Transactions for free?

Yes, for 14 days. The Blockchain API free trial includes Prepare Transactions and every other feature, with no card. It ends after 14 days or when its credits run out; after that, calls need a subscription, listed on the pricing page.

Does the Prepare Transactions API support Solana or Bitcoin?

Yes. Prepare Transactions works on 19 blockchains: the EVM chains and Tron, Bitcoin and the other UTXO chains, XRP Ledger, Solana (coins and SPL tokens), Tezos and Kaspa. It builds the unsigned transaction, with the inputs or the nonce and the fee filled in, for you to sign on your own server and then broadcast.

Can I prepare ERC-20 token and NFT transfers, or only native coin transfers?

Yes, both. The Prepare Transactions API supports native EVM coin transfers as well as fungible token (ERC-20) and non-fungible token (NFT) transfers from any address. It builds the unsigned transaction payload ready for you to sign locally.

How do I go from a prepared transaction to a confirmed on-chain transaction?

Prepare the unsigned EVM transaction with Prepare Transactions, sign it, then submit it with the Broadcast Signed Transaction endpoint. You can also estimate gas costs beforehand using the EVM Blockchain Fees endpoint.

Can I estimate gas fees for an EVM transaction before sending it?

Yes. CryptoAPIs provides an EVM Blockchain Fees endpoint to retrieve current fee estimates so you can set gas parameters before signing and broadcasting. This pairs directly with the Prepare Transactions workflow.

Can I test what an EVM transaction will do before broadcasting it?

Yes. CryptoAPIs offers an EVM transaction simulation endpoint that lets you preview the outcome of a transaction before it is signed and broadcast. This helps you catch failures or unexpected results without spending gas on-chain.

Start building with Prepare Transactions

14-day free trial, mainnet included. No card needed.

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