What Does the "Auto" Output Format Option Do?
Choosing "auto" as the output format means each image keeps its original format and only gets its file size reduced — a JPG stays a JPG, a PNG stays a PNG. The tool doesn't decide to convert it to something else.
"Auto" is not "pick the best format for me"
It's easy to assume "auto" means the tool judges which format best suits each image and converts accordingly — but what it actually does is simpler: keep the original format, only shrink the size. Deciding whether a given photo is well-suited to PNG is still a judgment call left to you; the tool doesn't make that format decision on your behalf.
When to use auto, and when not to
| Scenario | Recommendation |
|---|---|
| A mixed-format batch, just want smaller files with the same formats | Use auto |
| Want to standardize on one format (converting everything to WebP, say) | Choose that format explicitly, not auto |
| A batch that includes RAW files | Auto converts RAW to JPG; everything else stays unchanged |
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