Mempool / Pending


A blockchain mempool, short for memory pool, is a mechanism used by a blockchain to temporarily store valid but unconfirmed transactions before they are added to the blockchain. You can think of a mempool as a waiting room for transactions. When a user initiates a transaction, it is first broadcast to the network and is then added to the mempool of the nodes that receive it.

Miners and nodes on the network typically prioritize transactions in the mempool based on the transaction fees associated with them, as higher fees incentivize miners to include the transactions in the next block they mine.

Once a miner or validator confirms a transaction by adding it to a block and solving the cryptographic puzzle associated with that block, the transaction is removed from the mempool and is considered confirmed. Transactions that remain unconfirmed for a long time are eventually dropped from the mempool, as they are considered to have failed.

The mempool is an important component of a blockchain, as it allows for the efficient processing of transactions on the network. It ensures that valid transactions are not lost and that they are processed in a timely manner, while also allowing users to set the appropriate transaction fees to incentivize miners to prioritize their transactions.


Amberdata offers two ways to view mempool data that provide a wide variety of information related to transactions. You can view historical mempool data from as far back as January 2018 in the REST endpoint or real-time mempool data in the WSS endpoint. We offer mempool data for Bitcoin, Ethereum and Litecoin.

Amberdata allows you to query as much or as little mempool data as you need. You can set the date range for the query, whether to include the logs and functions and even the price.

In addition, we give you the option to query all transactions, pending transactions, completed transactions or failed transactions.

API Endpoints

/transactions mempool all


The mempool endpoint is available in the Blockchain Transactions namespace as well as WSS for a real-time view.

We have been collecting mempool data since 2018 and have one of the largest mempool data set in the industry. This is important to note due to the ephemeral nature of mempool data; what doesn't end up in the block itself, is lost forever.

Frequently Asked Questions

Which mempools do you have data for?

  • We have mempool data for Bitcoin, Litecoin and Ethereum.

How far back does your mempool data go?

  • It depends on the Blockchain network:
    • Ethereum = January 1, 2018
    • Bitcoin = December 20, 2019
    • Litecoin = January 9, 2020

Will your mempool data allow me to do time-in-flight analysis?

  • Yes. Since we have data as far back as January 2018, you can see how long a transaction stayed in the mempool before it was picked up by a miner/validator.

Can I see a live/real-time view of the mempool?

  • Yes. Using our WSS endpoint you can watch the mempool live.