JPEG XL Explained
Last updated: October 2026. This is a plain-English guide to JPEG XL — what the format actually is, why its support history has been so turbulent, which browsers and apps can open .jxl files today, and the one feature that makes it worth caring about even while the wider app ecosystem catches up. No jargon walls: every claim here has a practical takeaway attached.
What JPEG XL actually is
JPEG XL (files end in .jxl) is the successor format produced by the JPEG committee — the same working group that gave us the original JPEG back in 1992. It was finalised in 2021 and published as the ISO/IEC 18181 standard, developed by a research team that had previously built Google's PIK image format. Unlike most formats that grew features on top of an aging core, JPEG XL was designed from the ground up to do three jobs at once: excellent lossy photo compression, true lossless compression, and high-dynamic-range colour — in one container, chosen automatically per image.
Under the hood it carries two internal engines. A "varDCT" mode handles photographic content the way you would expect (it is a descendant of the same DCT idea that made JPEG work, but heavily modernised), while a "modular" mode handles lossless data, flat graphics and transparency. One practical bonus you notice immediately: .jxl images render progressively. A large photo fades in from blurry to sharp as it loads instead of painting top-to-bottom like JPEG, which is a genuine quality-of-life improvement on slow connections.
Why it is a real upgrade over JPEG
JPEG is thirty years old and it shows. To keep files small it throws away colour detail (chroma subsampling), creates blocky artefacts around edges, and never — not even in "highest quality" mode — keeps your original pixels. At comparable visual quality, .jxl photo files are commonly 30–50% smaller than an equivalent JPEG, without the blocking artefacts, and with the original pixel depth preserved where it matters. When you do need every pixel — scans, screenshots, graphics, archival masters — JPEG XL has a proper lossless mode that PNG-style formats approach but rarely match on size.
The bumpy history — the honest version
JPEG XL's story is a rare case of a technically superior format nearly being killed by ecosystem politics, and then clawing its way back. In February 2023 Google announced it was removing the built-in decoder from Chrome, arguing the format competed for resources with other priorities; because Chrome dominated browser engineering at the time, the move discouraged adopters for a couple of years. Firefox had enabled .jxl display back in 2021, then switched it off again while the underlying decoder library matured. Apple was quieter and earlier: Safari displays still .jxl images natively since version 17 (2023). Then the tide turned — Chrome reversed course and shipped JPEG XL decoding by default in Chrome 155 (announced 6 October 2026, using a memory-safe Rust decoder), and Firefox enables it by default in version 158 (October 2026). After years in the wilderness, JPEG XL is on by default in the two engines that moved first — Chrome since 155 and Firefox since 158 — while Edge and the wider app ecosystem are still catching up.
Which browsers and apps can open .jxl right now
- Chrome — decodes .jxl by default since version 155 (October 2026), including HDR and animation, though it still cannot create .jxl files.
- Firefox — enables .jxl display by default in version 158 (October 2026).
- Safari — displays still .jxl images since version 17 (2023); animation and progressive rendering are not supported there, and Edge is still trailing Chrome's enablement.
- Desktop apps and editors — most mainstream image editors still open .jxl only via plugins, and OS photo galleries vary widely. The format's own tooling (the libjxl reference encoder/decoder) is mature and fast, but application adoption lags the browsers.
This gap between "the format is excellent" and "not every app opens it yet" is exactly why conversion tools get used — and why you should read the "when not to use it" section below before committing your library to it.
JPEG XL vs WebP vs AVIF vs JPEG
The three modern still-image web formats each made different trade-offs. As a rough, directional summary (your mileage varies with image content, quality settings and encoder versions):
| Format | Since | Typical photo size vs JPEG | Lossless mode | Where it shines |
|---|---|---|---|---|
| JPEG | 1992 | baseline | No — always loses data | Universal compatibility, nothing else |
| WebP | 2010 (VP8-based) | ~25–35% smaller | Yes | Broad support, simple web images |
| AVIF | 2019 (AV1-based) | ~40–50% smaller | Yes, but heavy for flat graphics | Aggressive web compression, photo streams |
| JPEG XL | 2021 (ISO 2022) | ~30–50% smaller, plus lossless JPEG recompression | Yes — fast and efficient | Archives, editing masters, future-proof websites |
Two things the table understates. First, encoding speed: AVIF encoders borrow the video codec's famously slow pipeline, while JPEG XL encoding is dramatically faster — noticeable the moment you convert more than a handful of photos. Second, quality behaviour: AVIF can win at very aggressive low-bitrate compression, while JPEG XL tends to look better at high and near-lossless quality and keeps lossless files practical — which is why archivists and photographers, not just websites, care about it.
The killer feature: shrinking your existing JPEGs — losslessly
Here is the feature that makes JPEG XL useful today, even before every app opens it: lossless JPEG recompression. A .jxl encoder can take an existing JPEG and repackage it so that nothing — not a single pixel value — changes when it is decoded back, while typically cutting the file size around 20%. Your photo backup becomes smaller without becoming different. For anyone with tens of gigabytes of family photos sitting in JPEG, that alone justifies trying it, and it is precisely the kind of job that belongs on your own device: a batch of personal photos does not need to visit anyone's server to be recompressed. Our JPG to JPEG XL tool runs the encoder locally in your browser.
When to use .jxl — and when not to
Use JPEG XL when:
- You are archiving photos and want smaller files without any quality loss;
- You control the delivery — your own website, app or device — and can serve or fall back appropriately;
- You live on Chrome 155+, Firefox 158+ or Safari 17+ and simply want better-looking, smaller photos day to day;
- You need one format that covers both lossy snapshots and lossless masters.
Stick with JPEG or WebP when:
- You are sending an image into a system you do not control — email, upload forms, messaging apps, someone else's software;
- Your workflow depends on an editor that has no .jxl support yet;
- Maximum compatibility matters more to you than file size — the honest truth is that "will it open everywhere" still favours JPEG.
A pragmatic pattern many people settle on: keep masters in JPEG XL, share converted JPEGs. Our JXL to JPG tool exists for exactly that moment.
Try it yourself — without uploading anything
The fastest way to form an opinion is to convert a few of your own photos. Every JPEG XL tool on this site runs the real libjxl encoder or decoder as WebAssembly inside your browser tab — your files are never uploaded, and nothing changes about your library until you download the results. To go .jxl: JPG to JXL, PNG to JXL, WebP to JXL, HEIC to JXL, AVIF to JXL. To get back out: JXL to JPG, JXL to PNG, JXL to WebP, JXL to AVIF or JXL to PDF. The full overview lives on the JPEG XL converter hub.
Where the format is heading
The trajectory is clearly upward: Apple shipped still-image support, Firefox followed, and Chrome — the last big holdout — enabled JPEG XL decoding by default in version 155 (October 2026), with Edge expected to inherit it from Chromium. That shift is why the format has gone from "risky" to "safe to archive in": photos already stored as .jxl will open in mainstream browsers for years to come. The gap that remains is no longer browsers but apps — editors, phone galleries and upload forms — so for sharing you still want a conversion path out, which is exactly what these 38 local-first tools are built for. Choosing between formats? See our AVIF vs WebP vs JPEG XL comparison. Found an inaccuracy or want a format guide like this one? Tell us — we read everything.