AVI to MP4 Converter
Convert AVI to MP4 (Xvid, DivX, MJPEG) with H.264 and AAC in your browser, so your videos play on phones, TVs and the web. Free, no upload.
How it works
- Choose an AVI file.
- Keep the default quality (CRF 23) or pick another.
- Convert and download the MP4.
Tips
- CRF 23 looks like the original for most old AVI footage; CRF 28 gives a smaller file.
- If you mainly watch on a phone, pick 720p or 480p under Scale to shrink large sources.
Why convert AVI to MP4?
AVI is Microsoft's container from 1992. The AVI files around today mostly come from camcorders, older digital cameras and DVD rips, with Xvid or DivX (MPEG-4 Part 2) or Motion JPEG video and MP3 or PCM audio. iPhones, iPads, Safari and some smart TVs do not play those codecs, which is why the same file opens on one device and not on another.
This converter re-encodes the video to H.264 and the audio to AAC in an MP4 container, with the index moved to the start of the file so it can start playing before it has fully downloaded. That combination plays on practically every phone, browser and video editor.
Measured example
A 15-second, 720p, 30 fps Xvid AVI with MP3 audio (5.28 MB), in desktop Chrome on an Apple Silicon Mac:
| Quality | MP4 size | Time |
|---|---|---|
| CRF 23, AAC audio (default) | 2.42 MB | 15.5 s |
| CRF 28, AAC audio | 1.48 MB | 14.3 s |
Settings
H.264 compresses better than Xvid, so the MP4 is often smaller than the AVI at the same visual quality: less than half the size in the example above. Conversion ran at about real time for 720p; 1080p sources and phones are slower.
| Setting | Options | When to use |
|---|---|---|
| Quality (CRF) | 18, 23, 28, 32, 38 | Lower is better quality and a bigger file. 23 is the default; 18 for footage you will edit |
| Compression speed | Ultrafast to Slow | Slower presets give slightly smaller files and take longer; Veryfast is the default |
| Scale | Original, 720p, 480p, 360p | Only sizes below the source are offered |
| Audio | Re-encode to AAC, keep original, remove | AAC is the default because it plays everywhere |
Limits
Files up to 500 MB on a computer and 100 MB on a phone: the whole AVI is loaded into the browser's memory.
Interlaced camcorder and DV footage stays interlaced: the converter does not deinterlace, so combing on fast motion carries over to the MP4.
FAQ
What is the AVI to MP4 converter?
It re-encodes AVI videos (Xvid, DivX, Motion JPEG) to MP4 with H.264 and AAC in your browser, so they play on phones, TVs and the web. Your file is never uploaded.
How do I convert an AVI file to MP4 for free?
Choose the AVI, keep the default quality (CRF 23) or pick another, click Convert to MP4 and download it. There is no account or watermark.
Will I lose quality?
Re-encoding is lossy, but at CRF 23 the difference from an Xvid source is hard to see. Choose CRF 18 to stay closer to the original at the cost of a bigger file.
Why is the MP4 smaller than the AVI?
H.264 is a newer, more efficient codec than the Xvid or DivX video in most AVI files, so it needs fewer bits for the same picture.
Can I convert DivX or Motion JPEG AVI files?
Yes. DivX and Xvid use the same MPEG-4 Part 2 codec, and Motion JPEG is also supported. The measured example is an Xvid file with MP3 audio.
Will the MP4 play on an iPhone?
Yes. H.264 video with AAC audio in an MP4 plays natively on iPhone, Android, Windows, macOS and every major browser.
Can VLC convert AVI to MP4?
Yes. VLC's Convert/Save menu can, once VLC is installed, and HandBrake is another free desktop app for many files at once. This page needs no install and converts one file at a time.
How long does it take?
About as long as the video itself for 720p on a recent computer: 15.5 seconds for our 15-second test. 1080p files, long files and phones take longer. Files can be up to 500 MB on a computer and 100 MB on a phone.