Why are GIF files so big?
GIF compresses each frame on its own with LZW, a lossless method from the 1980s, and limits each frame to 256 colours. It can't take advantage of the fact that consecutive frames are almost identical, which is the main trick of every modern video codec. H.264 stores mostly the differences between frames, so the same animation typically takes a fifth to a tenth of the space, sometimes less.
That's why the GIFs you see on Twitter/X, Reddit, Giphy and Imgur are usually served as MP4s: a 10 MB GIF often plays from a 1 MB video, loads faster and looks smoother.
Where MP4 works and GIF doesn't
Converting matters most where GIF uploads are refused or handled badly:
- Instagram posts, Reels and Stories accept video, not GIF files.
- TikTok and YouTube Shorts only take video uploads.
- WhatsApp sends small MP4s as looping 'GIFs' in chats.
- PowerPoint, Keynote and Google Slides handle MP4 better than large GIFs, with smaller decks and smoother playback.
- Video editors treat MP4 as normal footage you can cut, speed up or add sound to.
What the converter does
Each GIF frame is decoded with its original timing, and the animation is encoded as H.264 at high quality (CRF 23) in an MP4. Frame dimensions are rounded to even numbers, which H.264 requires, so you lose at most one pixel row or column. The colours come through exactly: H.264 can show every colour the GIF has, and its slight smoothing usually makes the GIF's dithering pattern less noticeable.
GIFs have no sound, so the MP4 is silent. Transparent areas, which GIF supports and MP4 doesn't, become solid.
Looping
A GIF carries a loop setting inside the file; an MP4 doesn't. Social apps loop short videos automatically, and on a web page you get a GIF-like loop with the video tag's autoplay, loop, muted and playsinline attributes, which is how most sites replace GIFs today. In a desktop video player, turn on repeat.
If you need a few repetitions baked into the file, for example a 2-second loop that should run for 10 seconds on a platform that doesn't loop, convert it here and then join copies in a video editor.
Converted on your device
The conversion runs in your browser with ffmpeg, usually in a second or two for typical GIFs. Nothing is uploaded and no watermark is added. To go the other way, the Video to GIF converter turns a clip into an optimised GIF.
Replacing GIFs on a website
If you run a website, swapping big GIFs for MP4 is one of the easiest speed wins available. Google's Lighthouse and PageSpeed Insights even flag large GIFs with the audit 'Use video formats for animated content'. Convert the GIF here, then embed it with an HTML video element set to autoplay, loop, muted and playsinline. It plays inline on iPhone and Android, loops like a GIF, and usually loads in a fraction of the time.
Keep the original GIF as a fallback only if you need to support email newsletters, where many email clients don't play video. In ordinary web pages and apps, the MP4 alone is enough.