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HDR converter

An .hdr file is a Radiance RGBE image, the original high-dynamic-range raster format. Each pixel stores three 8-bit mantissas and one shared 8-bit exponent, so 32 bits per pixel cover a luminance range no ordinary 8-bit format can express. It is still the everyday container for the HDRI environment maps used to light 3D scenes.

Private for supported formats — processed in your browser

Convert supported files

Runs on your device

Drop HDR files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where HDR comes from

Greg Ward created the format for the Radiance lighting simulation system in the late 1980s, using the .pic extension before .hdr became the common spelling. Ward later added the XYZE variant for absolute CIE values and, in 2005, the higher-precision LogLuv encodings; despite its age the plain RGBE file is still what HDRI libraries publish.

How HDR works

  • RGBE encoding: three 8-bit mantissas plus one shared 8-bit exponent, 32 bits per pixel
  • About 1 percent relative precision across roughly 76 orders of magnitude of dynamic range
  • Plain-text header carrying FORMAT, EXPOSURE, GAMMA and PRIMARIES lines, then a resolution string such as -Y 1024 +X 2048
  • Scanlines are either flat or new-style adaptive run-length encoded per colour component
  • No alpha channel, no layers, and no tiling

When to use HDR

  • HDRI environment maps and sky domes for image-based lighting in Blender, Unreal, Unity and V-Ray
  • Photographic exposure brackets merged into a single scene-referred image
  • Lighting simulation output from Radiance itself
  • Distributing panoramas where file size matters more than per-channel precision

Strengths and limitations

Strengths

  • A quarter the size of a half-float OpenEXR for the same pixel count
  • Simple enough that decoders exist in essentially every 3D and rendering tool
  • Captures the full range of an outdoor scene in a single file

Limitations

  • Only about 1 percent precision per channel, and the shared exponent hurts saturated colours
  • No alpha, no extra channels, and no multi-layer support
  • Browsers cannot display it, so any web use needs a converted copy

Compatibility

Blender, Unreal Engine, Unity, 3ds Max, Maya, Photoshop, Affinity Photo, Luminance HDR and every major HDRI library handle .hdr files. No browser decodes it. This converter parses it in the page with three.js's RGBE/HDR loader, then renders the float pixels to 8-bit by clamping to the display range and applying the sRGB transfer function, so the conversion is deterministic and highlights above 1.0 clip rather than being reshaped by a guessed exposure.

The text header carries EXPOSURE, GAMMA, PRIMARIES, SOFTWARE and free-form comment lines. There is no EXIF, XMP or ICC profile block, and this converter's raster outputs do not carry the header lines across.

Convert HDR to another format