Ignore tracking parameters in caches

Tell caches to ignore tracking parameters with No-Vary-Search, so one page isn't stored many times.

By Erik Bergstedt, Agent Wranglers. Updated 20 October 2026.

How to do it

Send No-Vary-Search: params=("utm_source" "utm_medium" "utm_campaign" "gclid" "fbclid"), key-order on pages. Chromium uses it to match prefetched and prerendered pages. Other caches may ignore it.

Example

HTTP/1.1 200 OK
Content-Type: text/html; charset=utf-8
No-Vary-Search: params=("utm_source" "utm_medium" "utm_campaign" "gclid" "fbclid"), key-order

How to check

The header is present on HTML responses.

For agents: if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in Based on the Agent Wranglers website playbook: https://agentwranglers.se/playbook/website/performance/no-vary-search.