Dimensions
Balanced and Smallest redraw each frame on a smaller canvas. Fewer pixels usually mean less data, but fine detail becomes softer.
Local tool · measured output
GIF Compressor
Ready in your browser
01Choose and compress
Preparing…0%
02Measured result
Your compressed GIF appears here
The result stays in this tab until you leave or refresh.
Direct answer: choose a GIF, select a preset, and compare the measured input and output sizes. The file is decoded and rebuilt locally in this browser tab; it is not uploaded to SwapMyGIF.
Three real controls
What this GIF compressor changes
Palette size
Every output frame is mapped to a limited indexed palette. Fewer colors can reduce detail and may add banding in gradients.
Frame sampling
Smallest keeps alternate frames and adds each skipped frame's delay to the preceding kept frame. Motion may look less smooth.
Choosing between presets? Read GIF compressor settings explained: dimensions, colors, and frames for the exact preset table and timing rules.
Original method map
The file never leaves the tab
First-party evidence
Judge the actual output, not a promise
GIF compression is content-dependent. Flat artwork, gradients, transparency, motion, and the source encoder can all change the result. This tool therefore reports both byte counts after every run and warns when a preset does not produce a smaller file.
Implementation evidence: the current page uses the site's bundled GIF decoder and encoder, Canvas scaling, per-frame palette quantization, and no processing API. Format reference: MDN GIF guide.
Direct answers
GIF compressor questions
How can I compress a GIF?
Choose the GIF, start with Balanced, and run the compressor. Compare the measured result with the original. Use Smallest only when a smaller file matters more than dimensions, color detail, and smooth motion.
Does the compressor upload my GIF?
No. The selected file is read, decoded, redrawn, and encoded by JavaScript in the current browser tab.
Why can a compressed GIF look softer?
Reducing dimensions removes pixels, reducing the palette removes color choices, and dropping frames removes motion samples. Those are the same controls that can make the file smaller.
Will every preset make every GIF smaller?
No. The source encoder and image content matter. The result panel shows exact byte counts and warns when the new file is not smaller. See the first-party larger-output diagnosis for a 34-byte source that rebuilt to 64 bytes.
Does it preserve transparency?
The compressor can write binary transparent pixels when the rebuilt palette contains transparency, but it does not preserve source palettes or disposal metadata. Review the controlled transparency and disposal audit, then replay your complete result before downloading.
Can compression change GIF speed?
Yes. This compressor normalizes very short or missing decoded delays, and Smallest combines skipped-frame time into retained frames. See the five-frame timing audit for decoded before-and-after values from every preset.
Does it preserve a finite loop count?
No. The current encoder writes an endless-loop value into each rebuilt GIF. See the controlled loop metadata audit before compressing an animation that must stop after a set number of repeats.
Why can a small GIF still need substantial memory?
Compressed file bytes do not equal decoded pixel bytes. A 10,905-byte controlled source produced 12 MiB of RGBA frame patches before the preset was applied. Read the decoded-size audit for the exact method and limits.
Why can compression change GIF colors?
Every retained frame is mapped to a newly selected limited palette, even under Light. The controlled color audit isolates that palette step with a 256-color fixture.