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Request id

published · September 10, 2026

A request id is the identifier stamped on one API call, returned in the X-Request-Id header and repeated inside the response body.

A request id is the identifier stamped on one API call. It comes back in the X-Request-Id response header and is repeated inside the body — in meta.request_id on a success and in error.request_id on a failure — so the same string exists on both sides of the call.

What it is for

Quoting one to support turns "a call failed yesterday" into a row somebody can read. Every request an account makes is recorded with its id, the endpoint, the status, the typed error code, the credits it cost and how long it took; the account's own list is at /requests, and the support form offers the newest ids so nobody has to go and find one.

The header is exposed to browser JavaScript on purpose, because the documentation tells callers to read it and a browser cannot read a header that is not listed in the CORS policy.

What the record does not hold

Not the value the call was about. The route is stored as its template, never as its path, so a request log row says that a phone lookup happened and never which number. Rows are deleted after 30 days.

Related

markdown version: /glossary/request-id.md

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The Spaw API runs every check described here on each lookup, with an SMTP handshake that never sends mail. 10 free lookups a month, no card required.

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More glossary

  • Area-code overlay

    An area-code overlay is a new area code added over the same area as an existing one, instead of splitting it, so neighbours can hold different codes and local calls need ten digits.

  • Calling window

    A calling window is the span of local hours a sender contacts people in. Spaw answers in_call_window from the number's time zones: clock arithmetic, not compliance advice.

  • Fictional number

    A fictional number sits in a range kept out of service for films, TV and other fiction: 555-0100 to 555-0199 in North America, and ranges Ofcom, ARCEP, ACMA and ComReg reserve elsewhere.

  • International (exit) prefix

    An international prefix is what is dialled to leave a country before the calling code: 00 in most of the world, 011 in North America. Spaw reads it and suggests a fix in did_you_mean.

  • International network number

    An international network number sits under a calling code the ITU gives a global service rather than a country, such as +870, +881, +882 or +883, so its country is null.

  • Live carrier check (HLR lookup)

    A live carrier check asks the mobile networks, at the moment of the lookup, whether a number is in service, which network serves it and whether it is roaming. On Spaw it is not enabled.

  • Number pooling (thousands-blocks)

    Number pooling splits a North American central office code into ten blocks of a thousand numbers, each assigned to a carrier separately, so one code can hold several carriers' numbers.

  • Number portability

    Number portability lets a subscriber keep a phone number when changing carrier. The number's block stays listed under the carrier it was issued to, so block data names the original holder.