Why GIFs are so large
GIF dates from 1987 and was never designed for video. It stores animation as a run of complete still frames, each limited to a 256-colour palette, with only very basic compression between them. Modern video codecs do the opposite: they store one full frame and then only what changed, which is why the same three-second clip can be twenty times smaller as MP4.
| GIF | MP4 | |
|---|---|---|
| Colours | 256 per frame | Millions |
| Interframe compression | Minimal | Yes — the main saving |
| Transparency | 1-bit on/off | None |
| Typical size, 3s clip | 2–8 MB | 100–500 KB |
| Autoplays inline | Always | With muted + playsinline |
Making an MP4 behave like a GIF
The one real cost of switching is that a video element does not loop silently by default. Three attributes fix that, and the fourth stops iOS taking it fullscreen:
<video src="clip.mp4" autoplay loop muted playsinline></video>
muted is the load-bearing one: browsers refuse to autoplay anything that could make noise, so without it the video simply will not start.
Frequently Asked Questions
Why convert a GIF to MP4?
Size, almost entirely. GIF is a 1987 format that stores animation as a sequence of palette-limited still frames with no real interframe compression, so an animated GIF is routinely five to twenty times larger than the same clip as MP4. MP4 also supports far more than 256 colours, so gradients and video footage look better rather than banded.
Does this upload my GIF anywhere?
No. Decoding and video encoding both run on your own device through the browser WebCodecs APIs. You can watch your Network tab stay silent during the conversion, which is exactly why the tool is limited to browsers that implement those APIs rather than falling back to a server.
Why does it need Chrome?
The conversion uses ImageDecoder and VideoEncoder from the WebCodecs specification, which as of 2026 only Chromium browsers implement. Chrome, Edge, Opera, Brave and Arc all work. Safari and Firefox do not yet, and rather than quietly uploading your file to a server instead, the tool says so.
What happens to transparent areas?
MP4 has no alpha channel at all, so transparency has to become a solid colour. The tool defaults to white and lets you pick any colour before converting. If your GIF has a transparent background, choose the colour of the page it will sit on.
Will the MP4 always be smaller?
Nearly always, and often dramatically, but not universally. A very short GIF of a few flat-colour frames is already close to optimal, and video encoding adds container overhead that can exceed the saving. The result panel shows the before and after size either way, including when the file got bigger.
Does the MP4 autoplay like a GIF?
It can, but it needs three attributes rather than none: autoplay, loop and muted. Browsers block autoplay for anything with an audio track, so muted is what makes it behave like a GIF. Add playsinline as well so iOS plays it in place instead of going fullscreen.
Related tools
- Image converter — JPG, PNG and WebP, in every browser.
- Image compressor — shrink stills without changing format.
- Image resizer — change dimensions before converting to cut the size further.
- How to reduce image file size — where format choice fits in the order.