Chrome has set non-standardized 'Purpose: prefetch' header for the link-rel prefetch requests. But this is not aligned with the Fetch spec especially in the case to make a CORS request. We plan to renew this header to be a part of standardized one. Detailed plan is not yet decided. See the tracking bug entry. Prerender2 project may affect this header use.


Chrome uses non-standardized ‘Purpose’ header and this header is exempted in the CORS protocol checks. We may prefer to use a standardized one, or 'Sec-' prefixed headers that is explicitly exempted by the CORS spec.



Specification link

Unknown standards status - check spec link for status

Status in Chromium


Proposed (tracking bug)

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.

  • No signal
  • No signal
  • No signals


Last updated on 2021-12-19