Why is my GIF bigger than the JPG it came from?
Because the two formats compress opposite things. JPEG discards detail the eye is poor at seeing and codes what remains very efficiently, which is ideal for photographic gradients. GIF uses LZW, which rewards long runs of identical pixels, and a photograph, even reduced to 256 colors, has almost none. This is normal and it is the single best reason not to convert photos to GIF.
Why does the sky look striped?
That is banding from the 256-color palette. A smooth gradient across a sky might use several thousand distinct blues; the encoder has to pick at most 256 and map every pixel to the nearest. Since there is no dithering, the transitions between palette entries show as hard steps.
Is this an animated GIF?
No. This produces a single-frame GIF89a from one still image. Animation would require multiple frames, delay times, and a loop block, none of which this tool accepts or writes.
What should I use instead of GIF for a photo?
WebP for the web: it holds full color, supports transparency, and is dramatically smaller than either GIF or JPEG at the same quality. A well-tuned JPEG if you need maximum compatibility. PNG if the image is a graphic rather than a photograph and you need it lossless.
When does JPG to GIF actually make sense?
When something downstream only accepts GIF, or when the JPG is not really a photograph: a screenshot, a chart, a logo saved to JPG by mistake. Those have few distinct colors, so the palette is not a constraint and LZW compresses them well. Check the reported palette size: if it comes back well under 256, you are in the good case.
Is my image uploaded to convert it?
No. The JPG is decoded onto a canvas, quantised, LZW-compressed, and wrapped in GIF89a blocks entirely in JavaScript on your device. There is no server in the path.