Mozilla Firefox 156

Firefox 156 was released on September 14, 2026. We covered it in the news. A 156.0.1 bug fix update followed later in the month, and Firefox’s built-in updater applies it automatically.

What changed

A faster PDF viewer. Firefox’s viewer, pdf.js, renders PDFs in JavaScript inside the browser rather than through a native plugin. That design is why Firefox avoided a decade of PDF plugin exploits, and its cost has always been speed on large documents. 156 makes it up to 45 percent faster.

Lower memory use with large JPEGs. Tabs holding several high-resolution images were disproportionately expensive, which on machines with little RAM made the browser a frequent OOM killer target.

Installing

Most distributions package Firefox and update it quickly. Other options:

# Mozilla's own apt repository (Debian / Ubuntu), avoiding the snap
# see https://support.mozilla.org for the repository setup

# Flathub
flatpak install flathub org.mozilla.firefox

The tarball runs from any directory and keeps itself updated if your user can write to that directory:

tar xf firefox-156.0.tar.xz -C ~/.local/opt/
~/.local/opt/firefox/firefox

On Ubuntu, Firefox is a snap by default; our Snap vs Flatpak vs AppImage guide covers the trade-offs of each packaging route.

Verify Your Download

Mozilla publishes signed SHA256SUMS and SHA256SUMS.asc files in each release directory.