AVI files are often huge. A short clip from an old camera or screen recorder can run to gigabytes, which is too big to email or upload. The good news: AVI is one of the easiest formats to shrink, and the biggest saving usually comes from switching format, not from degrading the picture.
Why AVI Files Are So Large
AVI is a container, a wrapper that holds video and audio. The size depends on the codec inside it, and many AVI files use old or barely compressed codecs:
- Uncompressed or lightly compressed video, common in screen recorders and some capture cards.
- Older codecs such as DivX, Xvid, or MJPEG, which are far less efficient than modern H.264.
- High bitrates set by the original device and never reduced.
Modern H.264 (in an MP4) can often deliver similar-looking video at a fraction of the size. For the format background, see MP4 vs MOV vs AVI vs WebM.
Step 1: Convert to MP4 (Biggest Win)
For most AVI files, converting to MP4 with H.264 gives the largest reduction for the least loss. Follow converting AVI to MP4 or use the AllMediaTools Compress Video tool.
Expected results vary with the source. A file that’s currently uncompressed can shrink dramatically; one already using an efficient codec will shrink much less. Check the result before deleting the original.
Step 2: Lower the Bitrate if It’s Still Too Big
What bitrate means: it’s the amount of data per second of video, and it largely decides the size. If the MP4 is still too large:
- Reduce the bitrate a little at a time and watch for visible blocking in fast motion.
- Lower the resolution only if you don’t need it (1080p to 720p saves a lot, and looks fine on phones).
- Trim the clip to the part you need.
Each step trades some quality for size, so do the least you need and stop.
Step 3: Check Audio
AVI audio is sometimes uncompressed PCM, which is large. Converting it to AAC in the MP4 shrinks the audio with little audible loss.
Choosing a Target Size
| Where it’s going | Sensible target |
|---|---|
| Email attachment | Under about 20 MB, since many providers cap around 25 MB |
| Messaging apps | Check the app’s limit; WhatsApp and Discord both cap uploads |
| Website upload | Check the site’s limit, then leave some room |
| Archive | Don’t over-compress; keep a good-quality MP4 |
For general techniques, see how to compress video without losing quality.
Things to Watch
- Keep the original until you’ve watched the compressed file all the way through.
- Re-compressing repeatedly loses quality each time. Compress once from the original.
- Old AVIs with unusual codecs occasionally refuse to open in some tools. Try another converter if one fails.
Frequently Asked Questions
Does compressing an AVI reduce quality?
Converting to a more efficient codec can keep quality that looks the same to the eye while cutting size. Pushing the bitrate too low will cause visible loss.
What’s the best format to compress an AVI to?
MP4 with H.264 video and AAC audio is the most compatible and usually the smallest practical choice.
Why is my AVI file so much bigger than an MP4 of the same video?
AVI often holds older or uncompressed codecs. MP4/H.264 is far more efficient.
Can I compress an AVI without converting it?
You can re-encode it as AVI with a better codec, but MP4 is more compatible and almost always the better move.
How small can I make it?
It depends on the source, the content, and the quality you accept. Test with a short clip first.
Will compressed files play on my phone?
MP4 with H.264 plays on virtually every phone, TV, and computer.