Free online ERF to WEBP converter

What the ERF format is

ERF usually means Epson Raw Image File. Epson cameras create ERF files to preserve sensor data, exposure information, and camera metadata before processing. Raw converters such as RawTherapee, darktable, Adobe Lightroom, Adobe Camera Raw, and some versions of dcraw can open them.

ERF is also used by BioWare games for resource archives. A BioWare ERF archive is not an image and cannot be meaningfully converted directly to WEBP; first extract any embedded image assets with a compatible game-modding tool.

What the WEBP format is

WEBP is an image format designed for web delivery. Lossy WEBP commonly produces smaller files than JPEG at comparable visual quality, while lossless WEBP preserves pixel data and supports transparency and animation.

Use WEBP for browser publishing, website thumbnails, messaging, and applications that support modern web images. It is not a replacement for the original ERF because WEBP does not retain the raw sensor data needed for later white-balance, exposure, and highlight recovery adjustments.

How to actually convert ERF to WEBP

Using RawTherapee:

1. Open the ERF file in RawTherapee.
2. Adjust exposure, white balance, highlight recovery, noise reduction, and sharpening in the raw-processing controls.
3. Open the export settings, choose an output location, select WebP as the file format, and set quality around 85–95 for general sharing.
4. Save or queue the image for processing. RawTherapee develops the ERF and writes the resulting WEBP.

For batch conversion, first render the raw files to TIFF with dcraw, then encode the rendered files with the WebP command-line tools:

dcraw -T -6 -w image.erf
cwebp -q 90 image.tiff -o image.webp

The first command creates a 16-bit TIFF using the camera white balance; the second creates a lossy WEBP at quality 90. Replace the filenames with the actual output generated by dcraw. If your installed dcraw does not support the camera model, use RawTherapee or darktable instead.

You can also convert the file for free on the 101convert.com website without installing software. Uploading camera raw files may expose image metadata, and the service may not support every Epson camera model.

Quality and compatibility limitations

Develop the ERF before compression: converting raw sensor values directly to a display image requires demosaicing, color profiling, white-balance interpretation, and tone mapping. WEBP output is normally 8-bit per channel, so extreme exposure corrections should be completed during raw development.

Use lossy WEBP quality 90–95 for photographs intended for websites. Use lossless WEBP when every rendered pixel must remain unchanged, but expect larger files. Keep the original ERF and, if future editing matters, a 16-bit TIFF; WEBP is a delivery copy rather than a raw archive.

Check the resulting file in the software or browser that will use it. Older image viewers and some professional applications may lack WEBP support, while current browsers generally support it.