What does lossless mode do?

Without resizing, lossless mode stores the original JPEG reversibly so a compatible decoder can reconstruct the exact source JPEG. If you resize, the converter instead creates a pixel-lossless JXL from the resized image because the original JPEG bitstream no longer represents those pixels.

More about converting JPG to JXL

JPEG XL is a modern image format for high-quality photographs, responsive websites and long-term archives. Converting JPG to JXL can reduce storage or transfer size while keeping similar visual quality. Unlike ordinary re-encoding, JPEG XL can also wrap many existing JPEG bitstreams reversibly, preserving the ability to restore the exact original file.

Choose Lossy when the smallest practical file matters. The quality slider controls visual fidelity: higher values preserve more detail but produce larger files. Choose Lossless when exact preservation matters. With no resize, jpg.now uses reversible JPEG recompression; with resize enabled, it creates a pixel-lossless JXL of the resized image.

For websites, do not replace every fallback immediately. Put JXL first in an HTML picture element, then provide AVIF, WebP, or the original JPG for older browsers and software. Keep your source JPG until the JXL output has been checked in every part of your workflow.

When you'd use this

Reasons to convert JPG to JXL usually come down to compatibility, file-size, or specific feature requirements. Common situations:

  • An app or platform only accepts JXL uploads.
  • You need a feature unique to JXL (e.g. transparency, vector scaling, animation, multi-page pages, etc.) that JPG doesn't provide.
  • You're optimising file size — modern formats often produce smaller files than the older format you started with.
  • You need a single archival format across a project so files behave consistently in the same viewer.

How to do it in jpg.now

  1. Open the JPG → JXL tool on jpg.now.
  2. Drag your JPG file onto the drop zone, or click Select files. You can drop a whole folder of files at once.
  3. The output is fixed to JXL. If the format supports extra options (page size, transparency background, quality, EXIF stripping), tweak them in the right-hand panel.
  4. Click Convert. The job runs on our server and finishes in a few seconds for typical photos.
  5. Download the result. Files stay in storage for 24 hours and are then permanently deleted.

The entire flow is free for the first 10 jobs per day with no signup required. A free account doubles that quota; a premium plan removes the limit entirely.

Tips and common pitfalls

  • Use quality 88–92 for photographs where fine texture matters; lower the value for thumbnails and bandwidth-sensitive pages.
  • Choose lossless with no resize to preserve the source JPEG reversibly rather than decoding and re-encoding its pixels.
  • Keep a JPG, WebP or AVIF fallback when publishing JXL on the web because older browser versions remain in use.
  • Do not delete the original immediately. Verify colour, metadata and compatibility in your editor, CMS and CDN first.
  • Large lossless images take longer to encode than ordinary JPEGs, so allow extra processing time for high-resolution batches.
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