simulateTransaction | Solana

POST /9de47db917d4f69168e3fed02217d15b

simulateTransaction

cURL

curl --request POST \
  --url https://nd-326-444-187.p2pify.com/9de47db917d4f69168e3fed02217d15b \
  --header 'Content-Type: application/json' \
  --data '
{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "simulateTransaction",
  "params": [
    "AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABAAEDArczbMia1tLmq7zz4DinMNN0pJ1JtLdqIJPUw3YrGCzYAMHBsgN27lcgB6H2WQvFgyZuJYHa46puOQo9yQ8CVQbd9uHXZaGT2cvhRs7reawctIXtX1s3kTqM9YV+/wCp20C7Wj2aiuk5TReAXo+VTVg8QTHjs0UjNMMKCvpzZ+ABAgEBARU=",
    {
      "encoding": "base64"
    }
  ]
}
'

200

{
  "jsonrpc": "<string>",
  "id": 123,
  "result": {}
}

The Solana simulateTransaction method simulates sending a transaction. This method does not send a transaction, but rather runs the transaction and returns the result of the execution.

This method is useful for predicting how a transaction will affect the state of the blockchain without actually committing any changes. It can be used to estimate transaction fees, check for potential errors, and understand the effects of a transaction before sending it.

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Parameters

1. transaction (string, required) — a base64 or base58 encoded string representing the transaction to simulate.
2. config (object, optional) — configuration object containing:
   • encoding (string) — encoding used for the transaction data. Values: base58 (deprecated), base64 (recommended). Default: base58.
   • commitment (string) — the bank state to simulate against. Default: finalized.
   • sigVerify (boolean) — when true, verify transaction signatures. Default: false. Conflicts with replaceRecentBlockhash.
   • replaceRecentBlockhash (boolean) — when true, replace the transaction’s recent blockhash with the most recent blockhash from the bank. Default: false. Useful for simulating transactions with expired blockhashes. Conflicts with sigVerify.
   • minContextSlot (integer) — the minimum slot at which the request can be evaluated.
   • innerInstructions (boolean) — when true, include inner instructions in the response. Default: false.
   • accounts (object) — configuration for returning post-simulation account state:
     • addresses (array of strings) — array of account addresses to return.
     • encoding (string) — encoding for the returned account data. Values: base64, base64+zstd, jsonParsed.

Response

The response includes a result object with:

• err — null if the simulation was successful, otherwise a transaction error object.
• logs (array of strings) — log messages the transaction produced during simulation.
• unitsConsumed (u64) — number of compute units consumed by the transaction.
• accounts — an array of account objects (or null) corresponding to the accounts.addresses request field.
• returnData — data returned by the last program that invoked sol_set_return_data. Contains programId (string) and data ([base64_string, "base64"] tuple).
• innerInstructions — array of inner instruction sets (when innerInstructions: true in the request). Each set contains index (the instruction index) and instructions (array of inner instruction objects).
• fee (u64, nullable) — the transaction fee in lamports.
• preBalances (array of u64) — account balances before the simulation.
• postBalances (array of u64) — account balances after the simulation.
• preTokenBalances — token balances before the simulation.
• postTokenBalances — token balances after the simulation.
• loadedAddresses — addresses loaded from address lookup tables. Contains writable (array of strings) and readonly (array of strings).
• replacementBlockhash — present when replaceRecentBlockhash: true. Contains blockhash (string) and lastValidBlockHeight (u64).

Use case

A common use case for simulateTransaction is to estimate compute units, predict fee costs, and verify that a transaction will succeed before submitting it via sendTransaction. This is especially useful for:

• Estimating the exact compute units needed to set via ComputeBudgetProgram.setComputeUnitLimit
• Debugging failed transactions by inspecting logs and innerInstructions
• Previewing token balance changes with preTokenBalances and postTokenBalances
• Checking post-execution account state via the accounts config

Body

application/json

id · integer · default: 1

jsonrpc · string · default: 2.0

method · string · default: simulateTransaction

params · (string | object)[]

Transaction, as an encoded string

Response

200 - application/json

Simulated transaction details

jsonrpc · string

id · integer

result · object