getmempoolancestors

getmempoolancestors is a Bitcoin Core JSON-RPC method that walks the dependency graph of a pending BTC transaction backwards: given a txid that is still sitting in the node's mempool, it returns every other unconfirmed transaction that must be mined before it — its ancestors. Because Bitcoin uses an unspent-output (UTXO) model rather than accounts, a transaction can only be valid once the outputs it spends exist on-chain, so an unconfirmed transaction that spends an unconfirmed output forms an ancestor chain. Send the request to https://bitcoin.therpc.io/YOUR_API_KEY using positional params. By default the method returns a flat array of ancestor txids; pass verbose = true to get 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

• Identify the unconfirmed parent transactions that must be mined into a block before this transaction can itself confirm, so you know what is blocking a stuck BTC payment.
• Sum the ancestor fees and virtual sizes (with verbose = true) to compute an effective package fee rate in sat/vB and decide whether a child-pays-for-parent (CPFP) bump is worthwhile.
• Trace an entire unconfirmed dependency chain in the mempool — useful for wallets, exchanges, and explorers tracking long unconfirmed transaction packages.

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

Errors & troubleshooting

Common pitfalls

• The result only covers ancestors that are still unconfirmed. Once a parent is mined into a block it leaves the mempool, so it will no longer appear here even though the spending transaction still depends on it.
• 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 under fee pressure, or was never relayed to the node.

Supported networks

• Mainnet
• Testnet

See also

• getmempooldescendants
• getmempoolentry
• getrawmempool