Mozilla says Firefox will soon block web trackers by default, starting with trackers that slow page loads in Firefox 63 and cross-site trackers in Firefox 65
Mozilla today announced that Firefox will soon block web trackers by default. In conjunction, Firefox will also let users control what information they share with sites.
Context & Ripple Effects
This announcement is the starting gun for Mozilla's default-on privacy strategy: rather than waiting for users to install blocking extensions, Firefox would ship tracker-blocking as the out-of-box behavior, phased across two releases — performance-killing trackers in Firefox 63, cross-site trackers in Firefox 65 — alongside new controls over what information users share with sites.
The follow-through is visible in the related coverage: within a year Firefox had extended defaults to third-party cookies via the Lockwise-era release that flipped third-party cookie blocking on, then to fingerprinting and cryptomining in Firefox 69's expanded blocking, then social trackers plus a personalized privacy report in Firefox 70. By 2022 the approach had matured into surgical tooling, stripping Meta, HubSpot, and Marketo parameters from URLs — functionality Brave had pioneered.
First-order effects
- Ad-tech trackers lose passive access to Firefox users' browsing data at the browser layer, before any site-level consent flow applies — no action required from the user.
- Users on Firefox 63+ get faster page loads immediately, since the first blocking wave targets exactly the scripts that slow rendering.
Second-order effects
- Rival browsers face pressure to match default-on blocking or cede the privacy positioning — a dynamic the corpus shows playing out when Firefox later copied Brave's URL-stripping feature for Meta, HubSpot, and Marketo links.
- Advertisers and analytics vendors dependent on cross-site signals must rebuild measurement around first-party data or accept shrinking coverage as each Firefox release widens the block list.
Third-order effects
- Browser defaults are becoming de facto privacy regulation: what Chrome, Safari, and Firefox ship as on-by-default behavior now defines the practical rules of web tracking faster than legislation does.
- If the ratchet continues — cookies, then fingerprinting, then cryptomining, then social trackers — the third-party tracking industry structurally consolidates around the few channels browsers still permit, raising the value of first-party relationships.
The trend: Web browsers are converting privacy protection from an opt-in user task into a shipping default that tightens release by release, forcing the ad-tech ecosystem to re-architect around browser-imposed limits.