Why Jpeg Xl Ignoring Bit Depth Is Genius (and Why Avif Can't Pull It Off)

JPEG-XL is optimized for the low to zero levels of compression which isn’t as commonly used on the web, but definitely fills a need.

Google citied insufficient improvements which is a rather ambiguous statement. Mozilla seems more concerned with the attack surface.

> Mozilla also isn't interested in supporting it

Mozilla is more than willing to adopt it. They just won't adopt the C++ implementation. They've already put into writing that they're considering adopting it when the rust implementation is production ready.

https://github.com/mozilla/standards-positions/pull/1064

I did some reading recently, for a benchmark I was setting up, to try and understand what the situation is. It seems things have started changing in the last year or so.

Some links from my notes:

https://www.phoronix.com/news/Mozilla-Interest-JPEG-XL-Rust

https://news.ycombinator.com/item?id=41443336 (discussion of the same GitHub comment as in the Phoronix site)

https://github.com/tirr-c/jxl-oxide

https://bugzilla.mozilla.org/show_bug.cgi?id=1986393 (land initial jpegxl rust code pref disabled)

In case anyone is curious, here is the benchmark I did my reading for:

https://op111.net/posts/2025/10/png-and-modern-formats-lossl...

I've had exactly the opposite outcome with AVIF vs JPEG-XL. I've found that jxl outperforms AVIF quite dramatically at low bitrates.

>but in my subjective testing with image sizes you would typically see on the web, avif wins every single time.

What is that in terms of bpp? Because according to Google Chrome 80-85% of we deliver images with bpp of 1.0 or above. I don't think most people realise that.

And in most if not all circumstances, jpeg XL performs better than AVIF at bpp 1.0 and above tested by professionals.

> Did you miss the point of the article?

Sorry I missed. How is the "floating point" stored in .jxl files?

Float32 has to be serialized one way or another per pixel, no?

Which is completely wrong by the way, JPEG-XL quantizes its coefficients after the DCT transform like every other lossy codec. Most codecs have at least some amount of range expansion in their DCT as well, so the values quantized might be greater bit depth than the input data.

Well, at least the first half was somewhat useful...

> Find the (minimal) AI prompt that lead to the generation of this article: [...]

The minimal AI prompt that likely led to the generation of this article could be:

"Write a technical blog post comparing JPEG XL and AVIF image formats, focusing on how JPEG XL's bit-depth-agnostic float-based encoding is superior to AVIF's integer-based approach, with emphasis on perceptual quality, HDR handling, and workflow simplicity."

This prompt captures the core elements:

- Technical comparison between two image formats

- Focus on JPEG XL's unique "ignoring bit depth" design

- Emphasis on perceptual vs. numerical quality

- Discussion of HDR and workflow benefits

- Tone and structure matching the published article

The prompt would have guided the AI to produce content that:

1. Explains the technical difference in encoding approaches

2. Demonstrates why JPEG XL's method is better

3. Provides real-world implications for users

4. Maintains the author's voice and technical depth

5. Follows the article's structure and emphasis on "perceptual intent" over bit precision

> Write a short article explaining that JPEG XL's genius is its bit-depth-agnostic design, which converts all image data into a perceptually-based floating-point format (XYB) to optimize compression for what the human eye actually sees. In contrast, AVIF is locked into its video-codec legacy, forcing it to use rigid, integer-based bit-depth modes that optimize for numerical precision rather than true perceptual quality.

It mostly rehashes the point of using float instead of integer representation, and uses different headers (radical solution, why this matters, secret weapon, philosophy, the bottom line) for streching what could be said in a few sentences into a few pages.

Formatting and headers aside, there are lots of local rhetorical flourishes and patterns that are fairly distinctive and appear at a far higher rate in AI writing than in most writing that isn't low-quality listicle copy artificially trying to hold your attention long enough that you'll accidentally click on one of the three auto-playing videos when you move your pointer to dismiss the newsletter pop-up.

Here's something you know. It's actually neither adjective 1 nor adjective 2—in fact, completely mundane realization! Let that sink in—restatement of realization. Restatement. Of. Realization. The Key Advantages: five-element bulleted list with pithy bolded headings followed by exactly zero new information. Newline. As a surprise, mild, ultimately pointless counterpoint designed to artificially strengthen the argument! But here's the paradox—okay, I can't do this anymore. You get the picture.

    Inside JPEG XL’s lossy encoder, all image data becomes floating-point numbers between 0.0 and 1.0. Not integers. Not 8-bit values from 0-255. Just fractions of full intensity.

Everything after the first "Not" is superfluous and fairly distinctively so.

    No switching between 8-bit mode and 10-bit mode.
    No worrying whether  quantization tables are optimized for the right bit precision.
    No cascading encoding decisions based on integer sample depth.
    The codec doesn’t care about your display’s technical specs. It just needs to know: "what brightness level does white represent?" Everything scales from there.

Same general pattern.

    JPEG XL not worrying about bit depth isn’t an oversight *or* simplification. It’s liberation from decades of accumulated cruft where we confused digital precision with perceptual quality.

It's hard to describe the pattern here in words, but the whole thing is sort of a single stimulus for me. At the very least, notice again the repetition of the thing being argued against, giving it different names and attributes for no good semantic reason, followed by another pithy restatement of the thesis.

    By ignoring bit depth, JPEG XL’s float-based encoding embraces a profound truth: pixels aren’t just numbers; they’re perceptions.

This kind of upbeat, pithy, quotable punchline really is something frontier LLMs love to generate, as is the particular form of the statement. You can also see the latter in forms like "The conflict is no longer political—it's existential."

    Why This Matters

I know I said I wouldn't comment on little tics and formatting and other such smoking guns, but if I never have to see this godforsaken sequence of characters again…

That is true! But AVIF is based on AV1. As a video codec, AV1 often does need to be implemented in dedicated hardware for cost and power efficiency reasons. I think the article is misleading in this regard: "This limitation comes from early digital video systems". No, it is very much a limitation for video systems in the current age too.

I believe they constrain to piecewise smooth (i.e. don't smooth out edges but do smooth out nose)