testmempoolaccept

testmempoolaccept runs a signed Bitcoin transaction through the same policy and consensus checks the node would apply on broadcast, but stops short of relaying it. For each transaction it reports whether it is allowed, and when accepted returns the vsize and fee details (base, effective-feerate); when rejected it returns a reject-reason. Nothing is added to the mempool and no BTC moves — it is a pure pre-flight. Send the request to the Bitcoin JSON-RPC endpoint at https://bitcoin.therpc.io/YOUR_API_KEY.

Use cases

• Pre-flight a transaction to catch a rejection before you commit to broadcasting it with sendrawtransaction.
• Read the reject-reason to diagnose and fix fee or policy problems — insufficient fee, dust outputs, or a mempool conflict — before retrying.
• Validate a package of dependent (parent and child) transactions in one call on newer Bitcoin Core, useful for CPFP and package-relay flows.

Parameters

Response

Example request

1curl https://bitcoin.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5  "jsonrpc": "1.0",
6  "id": "therpc",
7  "method": "testmempoolaccept",
8  "params": [
9    [
10      "0200000001abcd...00000000"
11    ]
12  ]
13}'

Errors & troubleshooting

Common pitfalls

• A passing allowed: true result does not broadcast the transaction; it never enters the mempool. You still have to call sendrawtransaction to actually relay it.
• Older Bitcoin Core (pre-v22) and some providers accept only a single transaction in the rawtxs array. Package validation of multiple dependent transactions requires a newer node.

Supported networks

• Mainnet
• Testnet

See also

• sendrawtransaction
• decoderawtransaction
• estimatesmartfee