Betterfox is a user.js file for people who want a leaner Firefox: less telemetry, less tracking, some sensible optimizations. It doesn’t overhaul the browser, but quietly adjusts a series of default settings that most users would never touch.

Version 150, released recently, is a maintenance update, but it includes something worth paying attention to.

Trading speed for safety

The highlight here is new documentation on disabling JavaScript optimization compilers, the component known as JIT (just-in-time compilation). Here’s what that means: JIT transforms web page code on the fly into native processor instructions, making modern web applications much more responsive. The downside is it creates a real attack surface.

Google estimated that disabling these optimizers would have blocked roughly half of the JavaScript bugs actively exploited on Chrome. Microsoft came up with similar numbers when analyzing its own engine for Edge’s “Super Duper Secure Mode” feature.

Betterfox doesn’t disable JIT by default: some sites might break. But the new wiki section explains how to enable it and what to expect.

Everything else

Removed network.predictor parameters, which were already deprecated in Firefox 148 and pointless in the config file by now. Minor tweaks to the example policies.json file as well.

Firefox 150 itself adds a couple of useful things: the built-in PDF editor now lets you reorder, copy, delete, and export pages, and right-clicking on multiple selected tabs lets you copy all their links at once.