Guide
AVI to MP4: old videos that play on any phone
Drop an AVI file above and get an MP4 that plays on phones, TVs and social apps. The file never leaves your device.
In short
- This converter turns an AVI file into an MP4 with H.264 video and AAC sound.
- It suits old camera clips, Windows exports and videos kept in an archive.
- Most AVI video is re-encoded once at high quality, so it still looks the same.
- The MP4 is often smaller than the AVI you started with.
- Nothing is uploaded. Everything runs inside this browser tab.
AVI to MP4
Runs in your browser · files never leave this page
Drop a AVI file here
or
The engine reads the file first. An H.264 picture with AAC sound is copied into the MP4 with no re-encode. Anything else is written as H.264 + AAC.
Your file never leaves this page. The engine downloads once, the work happens in this tab, and there is no upload, no account and no storage. Close the tab and the file is gone unless you downloaded it.
More free tools: Video compressor · Video resizer · Video to MP4 · Video to MP3 · Video clipper · all tools
What is an AVI file?
AVI is an older Microsoft video format, first released in the early 1990s.
- AVI files come from old digital cameras, Windows editors and archives.
- Inside an AVI you often find DivX, Xvid or Motion JPEG video. The sound is usually MP3, or stored uncompressed, which is why old AVI files are so large.
- Phones, Macs and social apps often refuse to open an AVI file.
- An AVI can hold almost any video format inside, so one AVI opens on your computer and the next one does not.
What the converter does
It copies what an MP4 can hold as it is, and re-encodes only what it cannot.
- Copied: H.264 video and AAC sound go into the MP4 untouched. No quality loss.
- Re-encoded: any other video becomes H.264 at a high quality setting (CRF 23).
- Sound: any other sound becomes AAC at 160 kbps.
- Web ready: the MP4 is set up to start playing before it fully loads.
What happens to each part of your AVI file
The first video track and the first sound track are used. The rest is left out.
| Inside the file | What you get in the MP4 | How long |
|---|---|---|
| DivX or Xvid video | Re-encoded once to H.264 | Minutes for a long file |
| Motion JPEG video (old cameras) | Re-encoded to H.264, usually far smaller | Minutes for a long file |
| H.264 video | Copied as is | Seconds |
| MP3 or uncompressed sound | Converted to AAC at 160 kbps | Seconds |
Inside the file: DivX or Xvid video
- What you get in the MP4
- Re-encoded once to H.264
- How long
- Minutes for a long file
Inside the file: Motion JPEG video (old cameras)
- What you get in the MP4
- Re-encoded to H.264, usually far smaller
- How long
- Minutes for a long file
Inside the file: H.264 video
- What you get in the MP4
- Copied as is
- How long
- Seconds
Inside the file: MP3 or uncompressed sound
- What you get in the MP4
- Converted to AAC at 160 kbps
- How long
- Seconds
This is the whole editor
Highlight a phrase and a clip lands on those exact words. No timeline, no keyframes, no layers.
How to convert AVI to MP4
Four steps, all in this tab.
AVI to MP4 in four steps
Drop your AVI file
In the box at the top
The engine reads it
Which video and sound it holds
Copy or re-encode
Only what MP4 cannot hold is redone
Download the MP4
Saved to your device
How to see what is inside your AVI
Two AVI files can hold completely different video, and that decides how long this takes.
- Open the AVI in the free VLC player and look under Tools for Codec Information. On a Mac it is Window, then Media Information.
- If it says H.264, the video is copied into the MP4 and you are done in seconds.
- If it says DivX, Xvid or Motion JPEG, the video is made again frame by frame, which takes minutes for a long file.
- If VLC cannot play the file at all, the file is damaged and no converter will read it.
- When the conversion finishes, the tool tells you whether it copied the video or made it again.
Limits of a browser tool
Everything runs on your own device, so your device sets the limits.
- File size: up to 500 MB runs comfortably. Bigger files may run out of memory.
- Speed: the engine uses one processor core, so a long re-encode takes minutes.
- First run: the engine downloads once, about 32 MB. After that it starts fast.
- Phones: it works, but a laptop is faster and has more memory.
Questions people ask
- Will my AVI get smaller as an MP4?
- Often, yes. Old AVI formats need much more data than H.264 for the same picture. A Motion JPEG clip from an old camera usually shrinks a lot.
- Can I convert AVI to MP4 on a Mac?
- Yes. The converter runs in Safari, Chrome or Firefox on a Mac. You install nothing.
- Why does it say it cannot read my AVI?
- Your AVI holds an old video format this converter cannot read, or the file itself is damaged. Try the file in the free VLC player: if VLC plays it, the format is the problem, and VLC can save it as an MP4 for you. If VLC cannot play it either, the file is damaged.
- How long does AVI to MP4 take?
- Most AVI video has to be re-encoded, so plan on minutes for a long clip. Only an AVI that already holds H.264 video is copied in seconds.
- Is my AVI file uploaded anywhere?
- No. The tool runs inside this browser tab, so your AVI file never leaves your device. Only the engine itself is downloaded, about 32 MB, once per visit.
Want a finished video with captions, not just a converted file? Cutroom edits your clip for you. Your first video is free.