getmempooldescendants - Bitcoin

Example code for the getmempoolancestors JSON-RPC method. Complete guide on how to use getmempoolancestors JSON-RPC in GetBlock Web3 documentation.

This method returns all in-mempool ancestors of a transaction if it is in the mempool.

Parameters

Parameter	Type	Required	Description
txid	string	Yes	The transaction id (must be in mempool).
verbose	boolean	No	True for a JSON object, false for array of txids (default: false).

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "getmempoolancestors",
    "params": ["52273e0ce6cf3452932cfbc1c517c0ce1af1d255fda67a6e3bd63ba1d908c8c2", true],
    "id": "getblock.io"
}'

Axios

Request

Rust

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": {
        "abc123def456...": {
            "vsize": 141,
            "weight": 561,
            "fee": 0.00001410,
            "modifiedfee": 0.00001410,
            "time": 1700000000,
            "height": 820000,
            "descendantcount": 2,
            "descendantsize": 282,
            "descendantfees": 2820,
            "ancestorcount": 1,
            "ancestorsize": 141,
            "ancestorfees": 1410,
            "wtxid": "def456abc123...",
            "fees": {
                "base": 0.00001410,
                "modified": 0.00001410,
                "ancestor": 0.00001410,
                "descendant": 0.00002820
            },
            "depends": [],
            "spentby": ["52273e0ce6cf3452932cfbc1c517c0ce1af1d255fda67a6e3bd63ba1d908c8c2"],
            "bip125-replaceable": true,
            "unbroadcast": false
        }
    }
}

Response Parameters

Field	Type	Description
vsize	number	Virtual transaction size.
weight	number	Transaction weight.
fee	number	Transaction fee in BTC.
modifiedfee	number	Fee with fee deltas used for mining priority.
time	number	Local time when transaction entered pool.
height	number	Block height when transaction entered pool.
descendantcount	number	Number of in-mempool descendants.
descendantsize	number	Virtual size of in-mempool descendants.
descendantfees	number	Fees of in-mempool descendants (in satoshis).
ancestorcount	number	Number of in-mempool ancestors.
ancestorsize	number	Virtual size of in-mempool ancestors.
ancestorfees	number	Fees of in-mempool ancestors (in satoshis).
wtxid	string	Witness transaction id.
fees	object	Fee information breakdown.
depends	array	Unconfirmed transactions used as inputs.
spentby	array	Unconfirmed transactions spending this one's outputs.
bip125-replaceable	boolean	Whether transaction is replaceable (BIP 125).

Use Case

The getmempoolancestors method is essential for:

• Analyzing transaction chains in mempool

• Calculating CPFP (Child Pays for Parent) effectiveness

• Understanding transaction dependencies

• Building mempool visualization tools

• Debugging stuck transactions

• Implementing RBF strategies

Error Handling

Status Code	Error Message	Cause
403	Forbidden	Missing or invalid ACCESS-TOKEN.
-5	Transaction not in mempool	The specified txid is not in the mempool.

Integration With Web3

The getmempoolancestors method helps developers:

• Build CPFP fee calculators

• Create mempool dependency visualizers

• Implement transaction acceleration tools

• Debug unconfirmed transaction chains

• Analyze fee bumping strategies