Turn your MP4 into a GIF.
safe · secure · no server · works offline · fast
…or just start typing at the cursor.
↓ scroll for about & FAQsafe · secure · no server · works offline · fast
…or just start typing at the cursor.
↓ scroll for about & FAQ
Drop an .mp4 (or .m4v/.mov), open the
GIF tab, scrub to the moment you want and press convert. You get
the five controls every converter offers — trim (start and
duration), frame rate, width,
quality (palette size and dithering) and loop
— and a live estimate of the frame count and file size before you commit.
The difference is where it runs. Every other online converter uploads your video to a server, encodes it there and hands back a link; your footage sits on someone else’s disk, behind a queue, a 200 MB cap and often a watermark. OmniViewer encodes in the tab itself, with a real FFmpeg build compiled to WebAssembly. Nothing is transmitted, nothing is stored, and there is no account.
Quality is the other difference. A GIF holds at most 256 colours, so a careless
converter falls back to a fixed web palette and your video comes back banded and
muddy. OmniViewer runs FFmpeg’s two-pass palettegen /
paletteuse recipe: one pass measures the colours your clip actually
contains, the second maps every frame onto that measured palette with the dither
you chose. Read
how the exporter is built.
It’s one lens on OmniViewer’s MP4 File Viewer — GIF Export, Boxes & Metadata: drop a file and every tab is one click away. OmniViewer opens every file format, entirely in your browser — no upload, no server.
No. OmniViewer is a static page with no server-side processing: your MP4 is read directly by your browser and never leaves your computer. Even the fast-start fix and metadata edits happen locally, assembled from byte slices of your original file.
A tree of length-prefixed "boxes" (atoms): ftyp declares the format, moov is a small index holding every track’s codec, timing and byte offsets, and mdat is the actual compressed media. The player never scans mdat — it looks everything up in moov. MP4 is the ISO Base Media File Format, a descendant of Apple’s QuickTime .mov.
Because its moov index was written after the media data, a browser can’t learn the codecs or find any frame until the download reaches the end. That is the "fast start" problem. OmniViewer’s BOXES tab shows the verdict, and the Make streamable button moves moov to the front while patching every chunk offset.
No. The fix is pure byte surgery: the media bytes are copied untouched, only the moov index is rebuilt and the stco/co64 chunk-offset tables are patched to the new layout. Quality is bit-identical, and the rewrite streams — a 20 GB file is never held in memory.
Yes. The METADATA tab edits the iTunes-style tags (title, artist, album, date, genre and more) stored in moov/udta and downloads a re-tagged copy without re-encoding. It also shows the ©xyz GPS location atom, with a one-click Remove for a clean copy.
Yes — the GIF tab does it in the browser. Trim the clip on the scrubber, choose the frame rate, width, palette size, dither and loop count, and the tab encodes it locally with FFmpeg compiled to WebAssembly. There is no upload, no watermark and no account. Because the encoder holds the source in memory, the GIF tab caps the input video at about 512 MB — every other tab still opens a file of any size.
A GIF frame can use at most 256 colours. A converter that encodes straight from video falls back to a fixed, generic palette, which is what produces the muddy bands. OmniViewer runs FFmpeg’s two-pass recipe instead: palettegen measures the colours your clip actually contains, then paletteuse maps each frame onto that measured palette with the dither you picked.
Effectively unlimited. The box walk reads 16 bytes per box and skips the media data entirely, then parses only the small moov index — so a 20 GB movie costs a handful of tiny reads. Playback, raw and hex views read only the bytes needed on screen.
Yes. MOV, M4V and M4A use the same ISO BMFF container as MP4, so they get the same toolkit. OmniViewer identifies the format from the ftyp bytes, not the file extension, so a renamed file is detected for what it actually is.
Fragmented files — a skeleton moov followed by moof+mdat fragments — are detected and shown in the BOXES tree, but relocation rewrites are disabled: fragment offsets can’t survive a box shuffle, and such files are already built for streaming delivery.