No-Vary-Search

[liviutinta]

Request for position on an emerging web specification

• WebKittens who can provide input: @annevk

Information about the spec

• Spec Title: No-Vary-Search
• Spec URL: https://wicg.github.io/nav-speculation/no-vary-search.html
• GitHub repository: https://github.com/WICG/nav-speculation
• Explainer (if not README.md in the repository): https://github.com/WICG/nav-speculation/blob/main/no-vary-search.md

Design reviews and vendor positions

• TAG Design Review: https://github.com/w3ctag/design-reviews/issues/797
• Mozilla standards-positions issue: https://github.com/mozilla/standards-positions/issues/717

Anything else we need to know

No-Vary-Search is a proposed HTTP header which changes how various URL-keyed caches match, by letting them ignore some or all query parameters, or query parameter order. For example, if the order of the query parameter keys should not cause cache misses, this is indicated using

No-Vary-Search: key-order

If the specific query parameters (e.g., ones indicating something for analytics) should not cause cache misses, this is indicated using

No-Vary-Search: params=("utm_source" "utm_medium" "utm_campaign")

And if the page instead wants to take an allowlist-based approach, where only certain known query parameters should cause cache misses, they can use

No-Vary-Search: params, except=("productId")