# What is X-Request-ID?

> An HTTP header carrying a unique ID for one request, so it can be found in logs later.

Canonical: https://www.decimal.app/glossary/x-request-id · Last reviewed: 2026-09-23

X-Request-ID is a widely used HTTP header that tags each request with a unique identifier. Services log it and pass it along, and many APIs return it in responses so clients can quote it when something goes wrong.

## Why it matters

A request ID turns 'it failed sometime yesterday' into a single exact lookup. It's the fastest bridge from a customer's report to the logs and traces behind it.

## Best practices

1. Return it on every response. Especially errors, and show it in the UI where customers can copy it.
2. Ask for it in support forms. Make it an optional field for API issues.
3. Propagate it everywhere. Every service should log the same ID for the same request.

## How Decimal helps

When a ticket includes a request ID and timestamp, Decimal uses them as the starting point for its search across logs and traces.

## Related terms

- [Distributed Tracing](https://www.decimal.app/glossary/distributed-tracing): Following one request across every service it touches, with timing for each hop.
- [Logs](https://www.decimal.app/glossary/logs): Timestamped records of events a system emits as it runs.
- [Cannot Reproduce](https://www.decimal.app/glossary/cannot-reproduce): The status a ticket gets when engineering can't make the bug happen on their side.
- [Bug Report](https://www.decimal.app/glossary/bug-report): A write-up of unexpected behavior with enough detail for an engineer to reproduce it.

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