> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How signing APIs work

> Learn how Circle's signing APIs work for developer-controlled wallets when you manage broadcasting yourself.

Circle provides signing APIs that allow developer-controlled wallets to sign
transactions, messages, or typed data. Use these APIs when Circle doesn't
provide full [blockchain infrastructure](/wallets/blockchain-infrastructure) for
your blockchain, or when you prefer to manage broadcasting yourself.

For step-by-step instructions, see
[Sign Transactions on EVM Chains](/wallets/sign-tx-evm),
[Solana](/wallets/sign-tx-solana), or [NEAR](/wallets/sign-tx-near).

## Signing endpoints

Circle provides four signing endpoints for developer-controlled wallets. You
call one endpoint per request, depending on what you are signing:

* [Sign transaction](/api-reference/wallets/developer-controlled-wallets/sign-transaction):
  Sign a raw transaction for broadcasting to a blockchain.
* [Sign message](/api-reference/wallets/developer-controlled-wallets/sign-message):
  Sign an arbitrary message using EIP-191 (EVM) or a plain message (NEAR).
* [Sign typed data](/api-reference/wallets/developer-controlled-wallets/sign-typed-data):
  Sign structured data using EIP-712 (EVM only).
* [Sign delegate action](/api-reference/wallets/developer-controlled-wallets/sign-delegate-action):
  Sign a delegate action to authorize another account to act on your behalf
  (NEAR only).

## The signing flow

To sign and broadcast a transaction:

1. Build the raw transaction in your application, including nonce, gas
   parameters, and any blockchain-specific encoding. For example, NEAR requires
   Borsh serialization before signing.
2. Call the
   [Sign transaction](/api-reference/wallets/developer-controlled-wallets/sign-transaction)
   endpoint. Circle signs the transaction and returns the signed payload.
3. Broadcast the signed transaction to a node provider of your choice.

The following diagram illustrates this flow.

```mermaid theme={null}
sequenceDiagram
    participant App as Your application
    participant Circle as Circle Signing API
    participant Node as Your node provider

    App->>Circle: Send raw transaction to signing endpoint
    Circle-->>App: Return signed transaction
    App->>Node: Broadcast signed transaction
    Node-->>App: Transaction hash
```

When you manage broadcasting, you are also responsible for monitoring
transaction status, deposit detection, and balance retrieval.

## Signing for EVM wallets

For blockchains in the [Supported blockchains](/wallets/supported-blockchains)
Other EVM category, create a wallet using `blockchain: EVM` for mainnet or
`blockchain: EVM-TESTNET` for testing. These are virtual blockchain parameters
not tied to a specific blockchain. You specify the target blockchain using
`chainId` at signing time. For a list of supported testnet chain IDs, see
[EVM testnet chain IDs for signing](/wallets/sign-tx-chain-id).

<Warning>
  An EVM wallet shares the [same
  address](/wallets/unified-wallet-addressing-evm) as other wallets in the same
  wallet set. If you sign a transaction targeting a blockchain by [chain
  ID](/wallets/sign-tx-chain-id), the transaction executes from the wallet on
  that blockchain. For example, signing a transaction with chain ID `42161`
  executes from your Arbitrum wallet, even if you intended to sign for a
  different blockchain. Verify the chain ID before signing to avoid unintended
  transactions and stuck funds.
</Warning>

## SCA wallets and lazy deployment

[Smart contract account (SCA) wallets](/wallets/account-types#smart-contract-accounts-sca-and-msca)
use lazy deployment. The wallet contract is not deployed onchain until the first
transaction. Calls to
[Sign message](/api-reference/wallets/developer-controlled-wallets/sign-message)
or
[Sign typed data](/api-reference/wallets/developer-controlled-wallets/sign-typed-data)
before the wallet is deployed will fail. The wallet must complete at least one
onchain transaction before signing arbitrary messages or typed data.