getmempoolentry - Bitcoin

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

This method returns mempool data for a given transaction in the mempool.

Parameters

Parameter	Type	Required	Description
txid	string	Yes	The transaction id (must be in mempool).

Request

cURL

curl --location --request POST 'https://go.getblock.io/<ACCESS-TOKEN>/' \
--header 'Content-Type: application/json' \
--data-raw '{
    "jsonrpc": "2.0",
    "method": "getmempoolentry",
    "params": ["42c239dac42f146396888e0db814f7489f8b7c1aa773887f0249d03531e868c9"],
    "id": "getblock.io"
}'

Axios

Request

Rust

Response

{
    "jsonrpc": "2.0",
    "id": "getblock.io",
    "result": {
        "vsize": 141,
        "weight": 561,
        "fee": 0.00001410,
        "modifiedfee": 0.00001410,
        "time": 1700000000,
        "height": 820000,
        "descendantcount": 1,
        "descendantsize": 141,
        "descendantfees": 1410,
        "ancestorcount": 1,
        "ancestorsize": 141,
        "ancestorfees": 1410,
        "wtxid": "abc123def456789...",
        "fees": {
            "base": 0.00001410,
            "modified": 0.00001410,
            "ancestor": 0.00001410,
            "descendant": 0.00001410
        },
        "depends": [],
        "spentby": [],
        "bip125-replaceable": true,
        "unbroadcast": false
    }
}

Response Parameters

Field	Type	Description
vsize	number	Virtual transaction size.
weight	number	Transaction weight (BIP 141).
fee	number	Transaction fee in BTC.
modifiedfee	number	Fee with fee deltas used for mining priority.
time	number	Local time transaction entered pool (Unix timestamp).
height	number	Block height when transaction entered pool.
descendantcount	number	Number of in-mempool descendant transactions.
descendantsize	number	Virtual size of in-mempool descendants.
descendantfees	number	Modified fees of in-mempool descendants (satoshis).
ancestorcount	number	Number of in-mempool ancestor transactions.
ancestorsize	number	Virtual size of in-mempool ancestors.
ancestorfees	number	Modified fees of in-mempool ancestors (satoshis).
wtxid	string	Hash of serialized transaction with witness data.
fees	object	Fee breakdown object.
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).
unbroadcast	boolean	Whether transaction is waiting to be broadcast.

Use Case

The getmempoolentry method is essential for:

• Checking if a transaction is in the mempool

• Getting detailed fee information for unconfirmed transactions

• Monitoring transaction confirmation status

• Analyzing transaction priority

• Building transaction tracking systems

• Implementing fee estimation tools

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 getmempoolentry method helps developers:

• Build transaction status trackers

• Create confirmation time estimators

• Implement mempool monitoring dashboards

• Analyze transaction fee effectiveness

• Support RBF decision-making