Firefox 153 arrived on July 21 with three changes developers will care about: an extension security tightening that has already broken workflows, real GPU video decode on Linux that eliminates years of NVIDIA workarounds, and experimental JPEG XL support that adds Firefox to a list of browsers converging on the same image format. The extension change is the one most people will discover from user bug reports.
Extensions Can No Longer Read Local Files by Default
This is the one to act on now. Before Firefox 153, any extension holding the “Access your data for all websites” permission could read file:// URLs without additional prompts. That permission bundle has been split apart.
Starting with Firefox 153, local file access requires a separate explicit permission: “Access local files on your computer.” It is off by default for all extensions — including ones already installed and previously working. The upgrade does not prompt users; it silently revokes what was implicit access.
Affected extensions include anything that reads local HTML or PDF files, injects scripts into pages opened from disk, or relies on file:// URLs for local development testing. If users are reporting that an extension stopped working after a Firefox update, this is why.
The fix: go to about:addons, select the extension, open Permissions, and toggle “Access local files on your computer.” For extension developers, test your manifest against Firefox 153 now and update your install documentation. Enterprise deployments can pre-grant this permission centrally via Firefox policy. For background on the full WebExtensions API changes in Firefox 153, Mozilla’s add-ons blog has the complete rundown.
This aligns Firefox with Chrome, which has required explicit file:// permission for extensions since 2012. Firefox is fourteen years late to the same security model — worth noting.
Vulkan Video Finally Fixes Linux GPU Decode for NVIDIA
The Linux video situation in Firefox has been a known frustration. VA-API was the standard hardware decode path, but NVIDIA’s proprietary driver does not support VA-API natively. Hardware-accelerated video in Firefox on NVIDIA Linux required installing nvidia-vaapi-driver — a third-party translation layer — and then hoping it worked with your driver version.
Firefox 153 adds a second decode path: Vulkan Video, implemented via FFmpeg’s Vulkan API. Decoded frames pass to Firefox’s rendering process through Linux’s dma-buf interface, keeping everything on-GPU with no PCIe roundtrip overhead. NVIDIA’s current proprietary driver supports Vulkan natively — no wrapper, no workaround. Linuxiac covers the full impact for NVIDIA Linux users.
Arm-based Linux systems get an even bigger upgrade. Devices running aarch64 Linux — embedded boards, single-board computers, newer Arm laptops — previously had no hardware video decode in Firefox at all. Vulkan Video fixes that entirely.
The current rollout is through Firefox Nightly while Mozilla validates GPU and driver combinations before expanding to stable. To check if it is active on your system, open about:support and look at the Media section. If it is not there yet, it will be — or test in Nightly now.
JPEG XL Is Experimental in Firefox. Chrome Is Close. Pay Attention.
Firefox 153 adds experimental JPEG XL support via Firefox Labs, enabled through Settings. It uses the same Rust-based jxl-rs decoder that Chrome 145 adopted in February 2026. The timing matters more than the experimental label.
JPEG XL compresses roughly 30–50% better than JPEG at equivalent visual quality and 20–60% better than PNG for lossless content. It also supports progressive decoding, animation, HDR, and wide color gamut — one format for everything. The current browser support picture: Safari ships it by default since 2023, Chrome has it behind a flag and is expected to enable it by default in the second half of 2026, and Firefox is now experimental. When Chrome flips the switch, global support jumps from roughly 16 percent to above 85 percent.
The recommendation for production web apps: do not switch your image pipeline yet. AVIF and WebP remain the practical delivery chain. Use the <picture> element to serve JPEG XL to supporting browsers with a JPEG fallback. Get familiar with the conversion tooling — cjxl, Squoosh, and most image CDNs already support JPEG XL. The production trigger is Chrome going default-on, and that is months away at most.
Other Changes Worth Noting
Firefox 153 also ships stable HDR video playback on Windows — HDR10 and HLG formats — requiring HDR mode enabled in display settings. It is a meaningful gap closure vs Chrome on Windows video quality; if you build video-heavy web apps targeting Windows, test the playback path. (If HDR pipeline tooling interests you, OBS Studio 32.2’s SDR-to-HDR conversion is the production side of the same shift.)
DevTools gains a Local Mode option that loads a local directory under a custom origin without requiring a local web server. This matters specifically for testing Service Workers, localStorage, or any API that refuses to operate on file:// URLs. Built-in PDF merging rounds out the user-facing highlights. Firefox 153 also becomes the new ESR release, replacing Firefox 140 ESR — enterprise teams should confirm their extension and policy configuration before the auto-upgrade window closes.
Three Things to Do Now
- Check your extensions. Open about:addons in Firefox 153 and verify that any extension needing local file access has the new permission enabled. Update your documentation. Review the Firefox 153 release notes for the full list of changes.
- Test JPEG XL in Firefox Labs. Enable it via Settings and run your site’s images through a JPEG XL converter. Note the size differences. You want this data before Chrome enables it by default.
- Linux/NVIDIA users: check about:support. Look at the Media section to confirm whether Vulkan Video is active. If not, test in Firefox Nightly. The MDN developer release notes cover the full API surface changes for the release.
