# Tracking parameters in links

> What utm_, fbclid and similar parts of a link do, how Firefox and Safari strip them, what the EDPB says about tracking links, and a private link cleaner.

- Canonical URL: https://antitrackingsoftware.com/tracking-parameters-in-links/
- Source: [Mozilla, Query Parameter Stripping (Firefox Source Docs)](https://firefox-source-docs.mozilla.org/toolkit/components/antitracking/anti-tracking/query-stripping/index.html)
- Checked: 2026-10-22

This page includes a free interactive tool that runs in the browser and sends no data. The figures and rules it uses are the ones stated on this page, with their sources.

## In short
- **A link can carry an identifier.** Parts added after a question mark, such as `fbclid`, `mkt_tok` or `utm_source`, can tell a site where you came from, or tie your click to a campaign or a person.
- **Firefox strips a list of them.** Mozilla's documentation says query stripping removes known tracking parameters before you navigate, and that it is on by default in Enhanced Tracking Protection Strict mode ([Mozilla](https://firefox-source-docs.mozilla.org/toolkit/components/antitracking/anti-tracking/query-stripping/index.html)).
- **Safari does it in Private Browsing.** WebKit says Private Browsing removes known tracking query parameters before navigation ([WebKit](https://webkit.org/blog/15697/private-browsing-2-0/)).
- **EU regulators treat tracking links as tracking.** See [EU rules](https://antitrackingsoftware.com/eu-rules-on-tracking-and-fingerprinting/).

## The Mozilla list
The initial list in Mozilla's documentation names these parameters: `mc_eid`, `oly_anon_id`, `oly_enc_id`, `__s`, `vero_id`, `_hsenc`, `mkt_tok` and `fbclid` ([Mozilla](https://firefox-source-docs.mozilla.org/toolkit/components/antitracking/anti-tracking/query-stripping/index.html)). The documentation says the real list comes from a preference and from Remote Settings, so it changes, and sites on an allow list are skipped.

## How it works
Mozilla's page says stripping happens when a page loads, when the browser loads an address and during HTTP redirects. It also notes that the release version keeps the feature to Strict mode, a longer list runs in Nightly, and it was considering Private Browsing.

## Clean a link yourself
The tool above removes the eight Mozilla parameters, plus `utm_` ones, `gclid` and `msclkid`, which we added because they are common. It works on the text you paste; it does not open the link. If a link stops working after cleaning, a parameter it needed was removed: use the original.

## Why it helps, and its limits
- **It helps** when you share a link: your name or campaign tag does not travel with it.
- **It does not hide you from the site you visit.** The site still sees your IP address and browser details, which is where [fingerprinting](https://antitrackingsoftware.com/browser-fingerprinting-techniques/) starts.
- **It does not stop trackers that do not use parameters.**

*Outside this page:* We did not test any browser's stripping ourselves, and we did not read a full current list. Mozilla's page says the list is stored outside the page.

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Anti-Tracking Guide · Contact: contact@antitrackingsoftware.com