The answers below cover the questions we expect most often. For a full walkthrough of the converter, read the how-to guide; for background on the format, read what JPEG XL is.
Privacy in one paragraph
The converter is a static web page. When you add images, your browser reads them from your device and converts them with WebAssembly code that was downloaded with the page. There is no upload endpoint, no account and no image analytics. The full details are in our privacy policy.
Quality in one paragraph
JPG files are recompressed losslessly by default: the JPEG’s compressed data is stored more efficiently without being decoded, and the tool checks in your browser that the original can be restored byte for byte. PNG files are converted losslessly by default. Only the modes that say so — Visually lossless, Balanced and Custom — discard information.
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Frequently asked questions
Are my images uploaded to a server?
No. All conversion happens inside your browser with WebAssembly. After the page has loaded, your files are read from your device, converted on your device and saved back to your device. Our automated tests check that no network request carries image data during conversion.
How can I check that nothing is uploaded?
Convert one image so the converter is cached, then disconnect from the internet or switch on airplane mode and convert another. It keeps working. You can also open your browser's developer tools and watch the Network tab while converting.
Is it really free? What is the catch?
There is no sign-up, limit or watermark. The site may show clearly labelled ads in the future to cover its costs; ads would never be placed inside the converter, and images would still never leave your device.
Does converting to JPEG XL reduce quality?
Not in lossless mode. JPGs are recompressed losslessly by default and PNGs are converted losslessly. The Visually lossless, Balanced and Custom modes re-encode pixels and are lossy by design.
Why is my JXL file bigger than the original?
It happens with small or already highly compressed images, and especially when re-encoding a lossy WebP. The tool always shows the real size and suggests keeping the original in that case.
Can I convert JXL back to JPG?
This version only converts to JPEG XL. If the JXL was made with lossless JPEG recompression, the libjxl tool djxl can restore the original JPEG exactly. A JXL to JPG/PNG converter is planned.
Is my photo's EXIF data kept?
Yes by default: EXIF, XMP and the colour profile are kept for JPGs, and EXIF and XMP are carried over for PNG and WebP. You can remove GPS location or all metadata in Settings. A metadata report after each file lists exactly what happened.
Is there a file size or number limit?
There is no artificial limit. The practical limit is your device's memory: very large images above a per-device safety threshold are flagged before conversion instead of risking a crash.
Which browsers does the converter work in?
Current versions of Chrome, Edge, Firefox and Safari on desktop and mobile. It needs JavaScript and WebAssembly. Displaying the resulting JXL files is a separate question; see the browser support page.
Does it work on iPhone and Android?
Yes, in current versions of Safari on iPhone and iPad and Chrome or Firefox on Android. Phones convert one image at a time and use a lower size limit than computers to avoid running out of memory.
What does the effort setting do?
Effort controls how hard the encoder searches for a compact encoding. Higher effort usually gives slightly smaller files but takes longer. It does not change the quality setting. On phones the maximum effort is capped to keep the device responsive.
Why does AVIF take so much longer than JPEG XL?
AVIF is based on the AV1 video codec, whose encoders do a lot of work to find efficient encodings. In this converter AVIF is optional and unticked by default; after the first AVIF file finishes, the tool estimates the time for the rest based on what it measured on your device.
Does the tool change the resolution of my images?
No. The output has the same width and height as the input. Only the comparison preview is scaled down to fit your screen.
Does it work offline?
Yes. After you have loaded the page and converted one image, the converter is stored by your browser and works without an internet connection.
Can I install it as an app?
Yes. On Android and desktop Chrome or Edge an install button appears after your first conversion. On iPhone and iPad, use Share → Add to Home Screen in Safari.
Are animated images supported?
Not yet. Animated WebP and GIF files are detected and skipped with a notice.
What is the difference between JXL and JPEG XL?
None. JPEG XL is the format's name and .jxl is its file extension; people use both to mean the same thing.
Who makes this tool?
It is an independent project running on open-source codecs, mainly libjxl from the JPEG XL project. See the About and Open-source credits pages.