Analyze your MP4.
safe · secure · no server · works offline · fast
…or just start typing at the cursor.
safe · secure · no server · works offline · fast
…or just start typing at the cursor.
Drop an .mp4 and OmniViewer reads the moov index and
reports the file’s technical shape: the codec, the
resolution, the frame rate, the bitrate, the running time and
per-track details for video, audio and subtitle streams. It reads the index only,
not the media — so it’s instant and entirely local.
Stats are the fastest way to confirm what a clip actually is — H.264 vs HEVC, 1080p vs 4K, its true duration and track layout — before you play, convert or edit it. The same drop also plays the video, explores the box tree, edits metadata, and opens raw and hex views.
It’s one lens on OmniViewer’s MP4 File Viewer — Boxes, Metadata & Fast Start: 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.
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.