HDR to JXL Converter
Convert HDR to JXL in your browser. HDR files usually come from HDRI environment maps, 360° panoramas and lighting simulation; JXL is the better fit for archiving and future-proof high quality storage. You get a JPEG XL encoded with libjxl compiled to WebAssembly, lossy at the quality you choose or lossless. Nothing is uploaded.
- Processed locally
- No upload, no wait
- No sign-up
- No watermark
Drop images here
or choose files · paste with Ctrl/⌘ V
HDR expected · other image formats also work
How to use HDR to JXL
- 1
Add your HDR files: drop them here, choose them, or paste from the clipboard.
- 2
Set the quality.
- 3
Click Convert. Each file is decoded and encoded in a background thread on this device.
- 4
Download the .jxl files one at a time or together as a ZIP.
Why use Aback Images for hdr to jxl
Where the JXL goes next
JXL opens in Safari 17+, macOS 14 and iOS 17, GIMP, Krita, ImageMagick and the libjxl tools.
JXL next to HDR
A lossy JXL usually comes out far smaller than the HDR, which stores run-length encoded RGBE scanlines.
The first lossy pass
The HDR holds an 8-bit mantissa per channel sharing an 8-bit exponent (RGBE), 32 bits per pixel with nothing discarded yet. This conversion is the first lossy encode these pixels see, and hard edges and flat colour show it first.
Processed on your device
Your images are decoded, edited and encoded inside this browser tab by Web Workers. Nothing is uploaded to a server.
HDR vs JXL
What changes from HDR to JXL
Encoding: the HDR uses run-length encoded RGBE scanlines; JXL uses lossy VarDCT or lossless modular coding; existing JPEGs can be repacked without loss, and the download is a JPEG XL encoded with libjxl compiled to WebAssembly, lossy at the quality you choose or lossless.
Bit depth: an 8-bit mantissa per channel sharing an 8-bit exponent (RGBE), 32 bits per pixel in the HDR; JXL allows 8 to 16 bits per channel, or floating point, and the JXL written here has 8 bits per channel. The high dynamic range is mapped to 8 bits per channel, and values above white clip.
Colour: linear RGB (or XYZ in the XYZE variant) in the HDR; JXL supports sRGB, Display P3, linear and other spaces described in the codestream, written here as 8-bit sRGB.
Metadata: the HDR can carry a text header with FORMAT, EXPOSURE and optional comments; JXL can carry EXIF and XMP boxes in the container form, often stripped by encoders, but nothing is copied across.
About HDR
Radiance .hdr stores high dynamic range light values, widely used for 3D environment maps and HDRI lighting.
A Radiance file starts with '#?RADIANCE' (or '#?RGBE'), text lines such as FORMAT=32-bit_rle_rgbe and EXPOSURE, a blank line, a resolution line like '-Y 2048 +X 4096', then the scanlines.
HDR files usually come from HDRI environment maps, 360° panoramas and lighting simulation.
About JXL
JPEG XL is a next-generation format designed to replace JPEG. It compresses better than JPEG and WebP, supports lossless, HDR and progressive decoding, and can losslessly repack existing JPEGs.
A JPEG XL file is either a bare codestream starting with FF 0A or an ISO base media container whose 'jxlc' box holds the codestream. A recompressed JPEG keeps a 'jbrd' box that lets the original JPEG bytes be rebuilt exactly.
When converting HDR to JXL makes sense
JXL is the better choice for archiving and future-proof high quality storage, while HDR suits 3D lighting and environment maps.
JXL strengths: Excellent lossy and lossless compression; Progressive decoding and HDR; Huge image sizes. Drawbacks to weigh: Browser support is limited (Safari only by default); Few apps can open it yet.
Limitations
- Light values above 1.0 are clipped rather than tone-mapped, so the sun and bright sky turn flat white.
- Environment maps are 2:1 equirectangular panoramas, so the picture looks stretched near the top and bottom, as it should.
- Files in the XYZE variant cannot be read here; RGBE files, the common kind, can.
- Chrome and Firefox do not display JPEG XL by default, so it is not yet a format for websites; it suits archives and apps that support it.
- Lossless JPEG XL is usually smaller than PNG for the same pixels.
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Frequently asked questions
Does converting HDR to JXL lose quality?
JXL is lossy, so detail the eye barely notices is discarded to save space. The high dynamic range is mapped to 8 bits per channel, and values above white clip.
Which apps open JXL files?
Safari 17+, macOS 14 and iOS 17, GIMP, Krita, ImageMagick and the libjxl tools. It opens in Safari 17 and later; Chrome and Firefox do not display it by default.
Are my images uploaded anywhere?
No. Processing happens inside your browser with WebAssembly and Web Workers. The site only downloads the app code and codecs; your files never leave your device. You can confirm this with the live upload counter on the tool, or in your browser's network panel.
Can I process many files at once?
Yes. Drop a whole selection or folder. Files are processed in parallel on several worker threads, each result can be downloaded on its own, and everything can be saved as one ZIP.
Is it free? Is there a file limit or watermark?
It is free with no account, no watermark and no daily limit. The only limit is your device's memory: very large images (over roughly 100 megapixels) may be refused to keep the tab from crashing.