getmempooldescendants

getmempooldescendants is a Bitcoin Core JSON-RPC method that walks the dependency graph of a pending BTC transaction forwards: given a txid that is still in the node's mempool, it returns every other unconfirmed transaction that spends its outputs, directly or indirectly — its descendants. In Bitcoin's UTXO model a transaction's outputs can be spent before that transaction confirms, so an unconfirmed transaction can already have a chain of unconfirmed children riding on top of it. Send the request to https://bitcoin.therpc.io/YOUR_API_KEY with positional params. By default it returns a flat array of descendant txids; pass verbose = true to receive an object keyed by txid carrying the same per-transaction fields as getmempoolentry (vsize, weight, fees in BTC, ancestor/descendant counts, and more).

Use cases

• Find the unconfirmed child transactions that already spend this transaction's outputs, so you understand what else in the mempool depends on it confirming.
• Assess the size and fee weight of the descendant package (with verbose = true) before attempting a replace-by-fee (RBF) replacement — replacing a transaction also evicts its descendants, so you need to know what would drop out.
• Trace forward spends through the mempool to map out an unconfirmed transaction tree, which wallets and explorers use to predict confirmation behaviour.

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": "getmempooldescendants",
8  "params": [
9    "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b",
10    false
11  ]
12}'

Errors & troubleshooting

Common pitfalls

• The result only covers descendants that are still unconfirmed. A child that has already been mined into a block leaves the mempool and will not appear here, even though it spent this transaction's outputs.
• The method errors with code -5 if the txid you pass is not currently in this node's mempool — for example because it has already confirmed, was evicted, or was never seen by the node.

Supported networks

• Mainnet
• Testnet

See also

• getmempoolancestors
• getmempoolentry
• getrawmempool