Which image formats can SlashImage optimize?
1 min read · Last updated June 2026
SlashImage optimizes JPEG, PNG, WebP, and AVIF. Any other file type is left exactly as you uploaded it and shown as Format not supported in the Media Library.
Supported formats
| Format | Notes |
|---|---|
| JPEG | The usual format for photographs. |
| PNG | Common for logos, screenshots, and graphics. Opaque PNGs can optionally be converted to JPEG. |
| WebP | A modern format that is already compact. |
| AVIF | The newest format, with the smallest files. |
For optimized images, SlashImage also generates WebP and AVIF versions for delivery, whatever the original format - as long as Generate WebP and Generate AVIF are on (both are on by default). See How WebP and AVIF delivery works.
Everything else
GIF, SVG, PDF, TIFF, BMP, and similar files are not optimized. SlashImage leaves them untouched, and the SlashImage column shows Format not supported.
See also
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