Free Online RAW Photo Compressor | Lossless DNG for 18 Camera Formats

Why compress RAW camera files

A RAW file stores the unprocessed data straight off the camera sensor, so a single frame is often 20 to 60 MB. That is excellent for editing but heavy to store, back up or move between machines. This aggregated tool covers every RAW format we support on one page, so you do not have to hunt for a separate page for each camera. Whenever a model can be repacked without losing any data, the file is rewritten as a compressed but still lossless DNG; when that is not possible, it falls back to a high quality JPEG. If neither path makes the file smaller, your original is returned unchanged, so nothing is ever silently degraded.

Supported RAW formats and real test results

We only list formats we have actually run through the pipeline, together with measured size reductions from our own testing. No padding, and no formats we cannot truly process.

One known exception: a generic headerless .raw dump (for example from some GITUP action cameras) carries no camera identification and cannot be decoded, so it is not supported. All percentages above are real measurements from sample files and will vary with camera model, ISO and scene content.

How it works under the hood

Step 1 runs the open source dnglab encoder in lossless mode (LJPEG-92), rewriting the RAW as a compressed DNG. The embedded full size RAW copy, the large preview and the thumbnail are stripped so the DNG does not balloon in size. If the result is smaller, you receive a lossless DNG. Step 2 only triggers when dnglab does not support the camera model or the DNG would not be smaller: the dcraw decoder reads the sensor data using the camera white balance and AHD interpolation, and the output is saved as a high quality JPEG. Every job runs server side in an isolated sandbox, and temporary files are deleted the moment your download is ready.

How to use it

1. Drag your RAW files onto the upload area, or click to browse. You can add several files at once.

2. Adjust the quality slider if you want the JPEG fallback to be smaller. It has no effect on lossless DNG output.

3. Click compress. A progress bar shows the upload first, then server processing.

4. Download the result. Files that became a DNG keep the .dng extension; files that fell back are delivered as .jpg.

Lossless DNG versus JPEG fallback

A lossless DNG keeps one hundred percent of the sensor data and stays fully editable in Lightroom, Capture One, darktable and similar software, but the size reduction is modest, usually somewhere between 4 and 68 percent depending on the camera. The JPEG fallback is far smaller, yet it is an 8 bit, demosaiced, lossy image that suits sharing or previewing rather than heavy re-editing. A good habit is to keep the DNG as your master copy and export a JPEG only for delivery.

FAQ

1. Q: Is the DNG output really lossless?

   A: Yes. The dnglab lossless mode preserves every sensor value; only redundant embedded copies (a second full RAW, the large preview and the thumbnail) are removed. The image data is recoverable bit for bit.

2. Q: Why did my file come back as a JPEG instead of a DNG?

   A: Either the camera model is not supported by the dnglab encoder, or the lossless DNG was not actually smaller than the original. In those cases we fall back to a high quality JPEG so you still get a meaningful size saving.

3. Q: Will compression change how my photo looks?

   A: A DNG is visually identical to the original RAW. A JPEG fallback is a faithful render using the camera white balance, but it is 8 bit and lossy by nature, so keep the RAW master if you plan to edit heavily.

4. Q: Are my RAW files stored anywhere permanent?

   A: No. Processing is server side and temporary; your files and the results are deleted automatically once the download completes.

5. Q: What are the size limits?

   A: RAW files are processed one heavy job at a time for memory safety, so very large files may take longer. If a single file exceeds the limit it is returned unchanged rather than failing your whole batch.

More Image Processing Tools:

• Batch Image Compression
• Compressed folder images
• WebP Compressor
• PNG Compressor
• GIF Compressor
• SVG Compressor