A hash-based identifier for a serialized Bitcoin transaction.
Transaction ID (TXID) meaning
A transaction ID lets software and people refer to a specific transaction. For modern SegWit transactions, the TXID excludes segregated witness data, while the witness transaction ID identifies the full serialization including witness.
How it works in Bitcoin
Wallets and explorers display the TXID as hexadecimal text. Outputs are identified by the combination of the transaction ID and an output index, often called an outpoint.
A simple example
A wallet can look up a TXID to find whether the transaction is in its mempool or an accepted block and which outputs it created.
Why Transaction ID (TXID) matters
Transaction terms matter whenever bitcoin moves. Understanding them reduces mistakes involving fees, confirmation status, change outputs and irreversible destinations.
What people often get wrong
A TXID proves only which bytes were hashed. It does not by itself prove confirmation, payment purpose, legal ownership, or the identity of sender and recipient.
Quick checks before using the term
- Is the transaction only broadcast or already confirmed?
- Which outputs and fee are being created?
- Can wallet policy replace or delay it?
Apply these questions to the concrete example above. A precise answer is more useful than repeating the definition without naming the actor, rule or failure path.
Check the primary reference
This entry is written in plain English, but the technical source is available when you need exact protocol detail.
Bitcoin Developer Guide: Transactions ↗