A GIF stores at most 256 colours and compresses a photograph badly, which is why one saved from an old page or a chat thread is so much heavier than it looks. Measured on a 900-pixel-wide photograph: 290 KB as a GIF, 67 KB as a JPEG — the same picture, a quarter of the weight.
One, or up to twenty at a time. Files saved from chat apps, forums and old web pages all work.
The conversion happens on our side, and the gradients come back smooth — a GIF had to throw most of its colours away to fit a palette.
Each row has its own button, and a whole batch comes back as a single zip.
Because it was never meant to hold one. A GIF has a palette of at most 256 colours and compresses by finding repeated runs of pixels, which photographs do not have. A JPEG discards detail the eye does not notice instead, and that suits a photograph far better. The 900-pixel picture above went from 290 KB to 67 KB.
A single still image — the first frame. A JPEG cannot hold an animation, so if the movement is the point, this is not the tool you want. Use <a href="/compress-animated-gif">Make an animated GIF smaller</a> instead: it keeps every frame and hands back a GIF.
It is filled in. A JPEG has no way to store transparency, so whatever was see-through becomes solid. If you need the transparency kept, convert to PNG or WebP instead — both of those hold it.
On a photograph, usually better. The GIF had already discarded most of the colours to fit its palette and that damage cannot be undone, but the JPEG adds little of its own at these settings and does not band a gradient the way a 256-colour palette does.
Free Online Image Optimizer