XRequestId

X-Request-Id is an HTTP header used to identify and trace a single request as it travels through a distributed system. The value is intended to be unique for each request and is typically created by the first component that handles the request, then propagated through downstream services and included in logs and monitoring data. Clients may supply the header to help correlate client-side failures with server-side logs; if absent, servers or gateways often generate a value and return it in the response.

Format and generation: The value is commonly a UUID (often UUIDv4) or another opaque string that ensures uniqueness. It should remain stable for the life of the request and be forwarded by all downstream calls and components. The header is usually emitted in the response to assist clients in troubleshooting and to enable end-to-end correlation across services.

Industry use and standards: The header is widely adopted in web APIs and microservice architectures. There is no formal IETF standard for X-Request-Id itself, but it is a common convention that complements broader tracing practices. It is often used alongside distributed tracing mechanisms such as the W3C Trace Context to improve observability.

Best practices and security: Validate and sanitize incoming IDs to prevent header injection. Enforce reasonable length limits and prefer server-generated IDs when possible to avoid leaking internal details. Ensure the header is consistently propagated across all downstream requests to maintain accurate correlation in logs and monitoring data. Privacy considerations include avoiding exposure of sensitive internal identifiers in responses.