AVI to MP4 Converter

Bring an old AVI into MP4 so phones and modern players handle it.

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What to expect when converting AVI to MP4

Typical file-size change

30–60% smaller (typically)

Example

A 1 GB AVI typically becomes 400 – 700 MB as MP4 with H.264 at the same resolution.

Quality: Re-encoded from the AVI's codec (often older DivX/XviD) to modern H.264. Visual quality is preserved or improved.

Best for: modernizing legacy AVI video files, smaller storage, broad playback compatibility.

Avoid when: the AVI is your only master copy and you don't want any re-encoding loss.

Tip: AVI files from the early 2000s are usually larger than necessary. Converting to MP4 with H.264 keeps the visual quality and roughly halves the file size.

AVI to MP4 - Old Windows video, ready for a modern upload

AVI turns up in early-2000s camcorder footage, captures from utilities nobody runs any more, and batches of archive digitisation. MP4 is what makes that material playable today and acceptable to a platform. Expect it to take longer than converting a MOV, though: plenty of old AVI files are encoded with DivX or XviD and have to be genuinely re-encoded rather than simply repackaged.

AVI to MP4: modernizing a legacy format

AVI (Audio Video Interleave) was introduced by Microsoft in 1992. It lacks support for modern codecs, variable frame rates, subtitle tracks, and streaming. AVI files typically use older codecs (DivX, Xvid, or uncompressed) that produce much larger files than H.264/H.265. Converting to MP4 with H.264 re-encodes the video with a modern codec, typically achieving 50-70% file size reduction at equivalent or better visual quality.

Convert AVI to MP4 for playback on phones, tablets, smart TVs, and web browsers, most modern devices play MP4 natively but struggle with AVI. Also convert when file size matters: AVI's older codecs are far less efficient than H.264.

AVI vs MP4: Side-by-side

Technical comparison of the two formats, useful for deciding which to use, or for confirming what changes during conversion.

Property	AVI	MP4
Full name	Audio Video Interleave	MPEG-4 Part 14
Year introduced	1992	2001
Developer / standard body	Microsoft	MPEG
MIME type	video/x-msvideo	video/mp4
File extension	.avi	.mp4 / .m4v
Compression	Codec-dependent (DivX, XviD, MJPEG)	H.264 or H.265 codec
Color / data depth	Codec-dependent	8/10-bit
Max dimensions / size	Codec-dependent	Codec-dependent (up to 8K)
Transparency	No	No
Animation	No	No
Standard / specification	Microsoft RIFF	ISO/IEC 14496-14
Best for	Legacy video files, archival	Universal video compatibility, plays on every device

Frequently asked questions

What is AVI?

AVI is an older Microsoft video container, typically used for legacy editing software. Converting it to MP4 produces a file that opens on systems without AVI support.

How do I open AVI files?

On Windows: Media Player, or VLC for older codecs. On a Mac: VLC, QuickTime dropped most AVI codecs. The container is ancient and the codecs inside vary wildly. VLC is the reliable answer for anything from the DivX/XviD era.

Why are old AVI files so much larger than equivalent MP4s?

AVI files from the early 2000s typically used DivX, XviD, or even uncompressed video, all far less efficient than modern H.264. Converting to MP4 with H.264 keeps the visual quality and roughly halves the file size.

Will I lose video quality converting AVI to MP4?

There is a single re-encoding step, which introduces a small amount of additional compression. For most legacy AVI files (DivX-encoded), the quality loss is barely perceptible and is easily worth the size savings and compatibility improvement.