100% on-device
Compress an AVI in your browser
AVI is an old container holding old codecs — which is exactly why re-encoding one usually makes it far smaller. Done on your own device, with no upload.
How it works
- Drop your .avi. Old camcorder footage, DivX, XviD and MJPEG all read fine.
- Name a size. Type a limit and the bitrate is solved from your byte budget and the clip's duration.
- Download an MP4. H.264/AAC — smaller than the original at the same quality, and playable this decade.
An AVI’s size comes from the age of its codec, not from its resolution
AVI dates to 1992 and predates almost everything now put inside it. A typical one holds DivX or Xvid, 1990s Cinepak or Indeo, MJPEG where every frame is a standalone JPEG with no prediction between frames whatsoever, or DV from a miniDV camcorder - which runs at a fixed 25 Mbit/s whether the shot is a crowd scene or a blank wall.
That fixed cost is why a 480-line capture can outweigh a modern 1080p file. H.264 brings bidirectional prediction, variable block sizes, quarter-pixel motion compensation, in-loop deblocking and arithmetic coding; MJPEG has none of them and MPEG-4 Part 2 only some. The same picture simply needs a fraction of the bits once a modern codec describes it.
The other AVI problems: drifting audio and the 2 GB wall
AVI has no proper timing model for a variable frame rate and no clean way to carry variable-bitrate audio. VBR MP3 inside an AVI is a classic source of sound sliding out of sync as a long file plays on. Re-encoding hands back a container with a real timebase, which fixes the drift as a side effect rather than as a feature.
The original format addressed files with 32-bit offsets, capping them at 2 GB until the OpenDML extension arrived; old capture software simply split at the limit, which is why a camcorder transfer often turns up as numbered parts. Watch the size here - the file is read into the tab, and a large capture on one thread is slow and bounded by what the browser will allocate.
Questions
Is my video really not uploaded?
Yes — and not as a policy, as a fact of how it is built. There is no upload endpoint: the file is read straight into this browser tab and compressed by code running on your own machine. You can watch the Network tab while it works, or pull your Wi-Fi out mid-compression and it will still finish. Nothing is stored, nothing is queued, and there is no account.
Why does an AVI shrink so much?
Because of what is inside it. AVI files usually hold codecs from the 2000s — DivX, XviD, or worse, raw MJPEG where every frame is a separate JPEG. H.264 compresses far better than any of them, so the same footage at the same visible quality simply needs a fraction of the bytes. Old camcorder captures are the extreme case.
Will the quality get worse?
It is a re-encode, so strictly speaking yes — but from a codec this inefficient, the loss is usually invisible while the saving is enormous. If it matters, name a generous size limit: the tool spends every byte of the budget you give it.
My AVI will not open anywhere any more.
That is the other half of what this fixes. Modern phones, browsers and chat apps have no interest in AVI; an MP4 with H.264 plays on all of them. Compressing an old AVI here also quietly modernises it.
Other formats
The same workbench handles all of them — pick a tab above, or start from its own page: