Mozilla will add an option in Firefox 60 that will let users disable and hide the Firefox Sync option in the Firefox settings panel.
Firefox Sync is a Firefox feature that lets users synchronize and backup browsing details to a Firefox account, such as open tabs, installed add-ons, browsing history, browser preferences, bookmarks, and saved credentials. The feature is similar to Chrome's Sync feature.
Firefox Sync was initially released as Mozilla Weave as a Firefox add-on for Firefox 3.0. Mozilla embedded Weave into Firefox starting with Firefox 4.0, and rebranded the feature Firefox Sync with the release of Firefox 29.
While some users hate the feature, there are also many who find it incredibly useful, and Mozilla has no intention of removing the feature anytime soon from the main Firefox distribution.
But with Firefox 60, Mozilla engineers have decided to add a configuration option in the "about:config" panel that allows users to disable and hide the Firefox Sync UI from the Firefox user interface.
To disable and hide Firefox Sync, users should type about:config in their URL bar, press Enter, search for identity.fxaccounts.enabled and double click this option.
This option to disable and hide Firefox Sync is already included with Firefox Nightly. The stable version of Firefox 60 is scheduled for release in early May 2018.
The option was added at the request of Tor Browser developers as part of the Tor Uplift project, an initiative to bolster the Firefox codebase with some of the Tor Browser's unique privacy-focused features.
The Tor Browser is based on Firefox and they wanted a simple way to hide the Firefox Sync UI [1, 2], so their users wouldn't accidentally enable this feature and have personal details such as searchers and browsing history synced to a remote Firefox account.
This is the fourth major feature that lands in Firefox as part of the Tor Uplift project. The first three were:
Upcoming Tor Uplift plans include adding support for Firefox for blocking sites from fingerprinting users via VP8/VP9 codecs, and support for preventing Firefox from loading user details (username, emails, real names) into the browser's memory. Many other Tor Browser-based privacy enhancing features are also in the work.