24 Aug 2026

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Firefox Tooling Announcements: Happy BMO Push Day! (20260824.1)

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The following changes have been pushed to bugzilla.mozilla.org:

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24 Aug 2026 8:29pm GMT

Hacks.Mozilla.Org: Intent to Ship: JPEG XL

It isn't often that new image formats land in browsers. In the early 2000s we had JPEG, GIF, and PNG. The 2010s gave us WebP, which was a modest step up from JPEG. But the 2020s have given us two new image formats that are a big step up from previous formats: AVIF and JPEG XL.

We shipped AVIF back in 2021, and today we posted our intent to ship JPEG XL. Chrome are also intending to ship, and given there's already a partial implementation in Safari, the format will be supported across browsers before the end of the year.

Shipping JPEG XL securely

We added experimental support for JPEG XL behind a flag back in 2021. But, at 100,000 lines of multithreaded C++, we were concerned about the attack surface this added to Firefox.

So, we laid down a challenge to the JPEG XL team at Google Research: Build a safe, performant, compact, and compatible JPEG XL decoder in Rust, and we'll ship it. That challenge was met; Google Research built jxl-rs, and it's the core of our JPEG XL support in Firefox.

We also pushed for high quality integration tests as part of an Interop 2026 investigation area, and they're coming along nicely.

Progressive rendering

Although Safari shipped JPEG XL in 2023, their implementation lacked some key features of JPEG XL - our favourite is progressive rendering, which is something we pushed for in the Rust implementation.

Progressive rendering means the image can render as it's downloading.

An image of a fox curled up in a ball, sleeping amongst some grass, divided into four columns, showing JPEG XL progressive rendering. At 4% it's very blurry. At 15% you can tell it's a picture of a fox. At 50% the full image is clear, but not full resolution. At 100% it's full resolution.

Although the full image is 135 kB, with only a few kB downloaded the user can determine the subject of the image. Try the above demo image in a browser that supports JPEG XL & progressive rendering, like Firefox Nightly - move the slider to see how the image displays with just a portion downloaded.

JPEG XL vs AVIF

Browsers will now have two modern image formats for developers to choose from. Which you choose depends on your use-case.

For example:

A fox curled up in a ball, sleeping amongst some grass.

The image above is a 116 kB AVIF with a quality score (SSIMULACRA 2) of 62.8, meaning medium-high quality. To get the same quality, the JPEG XL image would be 134 kB.

At a SSIMULACRA 2 score of 80 (very high quality), the AVIF is 227 kB, and the JPEG XL is 264 kB.

But at lossless, the AVIF is 1.76 MB, and the JPEG XL is 1.45 MB. A lossless WebP is 1.55 MB.

Another example is a screenshot of the Interop 2025 scores:

Interop dashboard showing browser scores. At the top are two large circles: ‘Interop’ with a score of 95 in green, and ‘Investigations’ with a score of 36 in orange. Below are four browser scores in green circles: Chrome 99, Edge 98, Firefox 99, and Safari 98, each shown with their respective browser icons.

At a SSIMULACRA 2 score of 78 (very high quality), the AVIF is 11.6 kB, and the JPEG XL is 23.8 kB.

But at lossless, the AVIF is 164 kB, and the JPEG XL is 92 kB. A lossless WebP is 96 kB.

Although AVIF tends to produce smaller files at web-quality than JPEG XL, AVIF only has basic progressive rendering support. So, for very large images, it may be worth taking the filesize hit with JPEG XL.

The key is to test with a representative set of images for your site, at a quality that works best for your users, and remember to optimise for high density.

The post Intent to Ship: JPEG XL appeared first on Mozilla Hacks - the Web developer blog.

24 Aug 2026 3:32pm GMT

Jonathan Almeida: SSH access to Github over HTTPS

While using guest wifi during travels, I was trying to fetch some changes from a github remote and my git fetch is over SSH which happens over port 22. Most (TCP?) ports are blocked on public or hotel wifi, so with some help1 I learnt that Github serves SSH over 443 too.

A simple ssh config fixes this:

Host github.com
  HostName ssh.github.com
  Port 443
1

Claude.

24 Aug 2026 12:00am GMT