Which image formats can SlashImage optimize?
1 min read · Last updated June 2026
SlashImage optimizes JPEG, PNG, WebP, AVIF, and GIF. 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. |
| GIF | Compressed and kept as a GIF, plus a WebP version (animated if the GIF is). No AVIF, and GIFs are never resized. See How does SlashImage optimize GIFs?. |
For optimized images, SlashImage also generates WebP and AVIF versions for delivery, whatever the format - as long as Generate WebP and Generate AVIF are on (both are on by default). The one exception is GIF: it gets a WebP version but never an AVIF one. See How WebP and AVIF delivery works.
Everything else
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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