Firefox
Desktop & Mobile
Open Source
Firefox is a search engine that is very popular and is commonly-used in the online security and privacy community. It is owned by Mozilla, does not have any shady privacy policies, is lightning fast, and promises to never sell your data.
Notes:
When using Firefox, you should consider enabling HTTPS Only mode and Strict Enhanced Tracking Protection, on the "Privacy & Security" page in the Settings Menu. It is also recommended to install the uBlock Origin Extension, to block ads.
Waterfox
Desktop Only
Open Source
Waterfox is an open-source web browser for x64, ARM64, and PPC64LE systems. It is intended to be ethical and maintain support for legacy extensions dropped by Firefox, from which it is forked.
Notes:
System1 now own Waterfox, but Alex Kontos is still leading the direction of Waterfox and will be for the foreseeable future.
Unless you specifically register for a web service with Waterfox, they do not touch or view your personal data. For more info, see their ToS and Privacy Policy.
LibreWolf
Desktop Only
Open Source
LibreWolf is a modern secure web browser, being fork of Firefox, focused on privacy, security and internet freedom. It features no telemetry, an integrated ad blocker, fast updates, enhanced security, & more.
Notes:
LibreWolf is designed to increase protection against tracking and fingerprinting techniques, while also including a few security improvements. This is achieved through their privacy and security oriented settings and patches.
LibreWolf also aims to remove all the telemetry, data collection and annoyances, as well as disabling anti-freedom features like DRM.