Does converting AVI to MP4 reduce quality?

Yes, because this is a re-encode to H.264, not a remux. CRF 23 stays close for ordinary viewing. Old camcorder AVI is often already noisy, so the extra pass is less obvious than on a clean digital source. Keep the AVI if it is the only master.

Why not just rename .avi to .mp4?

The extension is not the codec. Players that trust the name still have to decode DivX, MJPEG, or whatever is inside. Renaming produces a file that fails in a more confusing way. Re-encoding writes H.264 and AAC, which is what phones actually implement.

Will interlaced camcorder video look right?

Not always. This preset does not deinterlace. You may see combing on movement. If that happens, deinterlace in a desktop editor and convert the progressive file. A hidden deinterlace here would blur progressive AVI that never needed that filter at all.

Will this work on iPhone or Android?

The converter runs in Safari and Chrome. Re-encoding is heavy, so a long AVI can overheat a phone or exhaust RAM. Prefer a computer for anything beyond a short clip..

Can I convert several AVI files at once?

Not currently. Each job keeps decoded frames in memory. Convert one, download the MP4, then drop the next. After the engine loads once, later files skip that download. A stack of holiday clips is still one conversion at a time.

Is it legal to convert AVI to MP4?

Re-encoding family camcorder files you recorded is the intended case. Re-encoding a commercial DivX you do not have rights to does not become lawful because the extension changed. Videozify does not store files and cannot check a licence.

AVI → MP4

AVI to MP4 Converter

Drop a file here

Click to browse, or paste a file from the clipboard.

Choose file

An AVI to MP4 converter re-encodes an old Windows or camcorder video into H.264 MP4 that phones and modern players open. Drop the file, convert, and download an MP4 you can AirDrop or upload without hunting for DivX codecs.

How to convert AVI to MP4

Drop your AVI file onto the box above, or click Browse to choose it from disk.
Confirm the selected clip is the one you want; this conversion re-encodes to H.264.
Press Convert and wait until the progress bar reaches one hundred percent.
Download the MP4 when it appears; the file saves only to this device.

Why convert AVI to MP4?

AVI is a Windows video container that camcorders, DivX rips, and early desktop editors used for years. DivX and Xvid home rips, MiniDV exports, old scientific captures, and family discs from the 2000s still show up as .avi. iPhone, current Android galleries, and most websites do not. The file is a time capsule with the wrong wrapper and, usually, the wrong codec.

Unlike MOV or MKV remux pages, this conversion re-encodes. AVI often holds MPEG-4 Part 2 (ASP), MJPEG, or other codecs MP4 players will not treat as H.264. Copying streams would produce an MP4 that still fails on a phone. libx264 plus AAC is the translation into what those phones actually decode.

That translation costs a generation of quality and some time. CRF 23 and ultrafast are chosen so a browser tab can finish without melting a laptop, not so you get an archival 2-pass encode. For a 20-year-old camcorder tape that already looks soft, the extra loss is usually less visible than "this will not open." For a carefully mastered AVI, keep the original beside the MP4.

Use this when a relative sends holiday video that plays only on an old PC, or when a lab archive is AVI and the journal portal wants MP4. If you only need the soundtrack from a lecture AVI, extract audio instead of paying for a full video re-encode.

If the new MP4 is still too large for email, compress the video. If you only needed a minute from a long tape capture, trim the video after it is in MP4.

AVI vs MP4: what's the difference?

	AVI	MP4
Extension	.avi	.mp4
Type	Legacy Windows container	MPEG-4 container
Typical size (4 min)	40–120 MB	Often similar after H.264
Compression	DivX/Xvid/MJPEG/other	H.264 + AAC
Quality	Source, often interlaced	Re-encoded (CRF 23)
Device support	Old PCs, VLC	Phones, web, modern editors

AVI is a legacy Windows video container that camcorders and DivX rips used for years and modern phones often cannot play.

Why isn't this a remux?

Because the codecs inside typical AVI files are not the ones MP4-on-iPhone expects. Stream-copying Xvid into an .mp4 extension is how you get a file that still needs ffdshow. This preset decodes the AVI and writes H.264 video at CRF 23 with the ultrafast preset, AAC audio at 128kbps, and fast-start.

Ultrafast favours finishing in a browser over squeezing every byte. The MP4 may be a bit larger than a slow encode of the same CRF. If you need a smaller file after it plays, compress the video as a second job.

Interlaced camcorder AVI can show combing after a naive encode. This preset does not include a deinterlace filter. If the MP4 has horizontal teeth on motion, deinterlace in an editor, then convert a progressive copy. Honesty beats a hidden filter that surprises progressive sources.

Why doesn't AVI play on my phone?

Mobile OS vendors standardised on MP4, H.264, HEVC, and more recently VP9/AV1 in limited cases. They did not ship DivX. A file that "works on the PC" often works because that PC still has an old codec pack. The phone never got one.

Email and cloud folders also block or transcode AVI. Uploading MP4 avoids a second mystery conversion by a mail gateway that might crush the picture worse than this tool. Convert locally, then send the MP4.

Some AVI files are actually a chain of images or an odd audio layout. If conversion fails, the file may be corrupt or use a codec ffmpeg.wasm cannot decode. That is a drop, not a retry loop — keep the AVI and try a desktop build of ffmpeg if this tab errors.

Frequently asked questions

Does converting AVI to MP4 reduce quality?: Yes, because this is a re-encode to H.264, not a remux. CRF 23 stays close for ordinary viewing. Old camcorder AVI is often already noisy, so the extra pass is less obvious than on a clean digital source. Keep the AVI if it is the only master.
Why not just rename .avi to .mp4?: The extension is not the codec. Players that trust the name still have to decode DivX, MJPEG, or whatever is inside. Renaming produces a file that fails in a more confusing way. Re-encoding writes H.264 and AAC, which is what phones actually implement.
Will interlaced camcorder video look right?: Not always. This preset does not deinterlace. You may see combing on movement. If that happens, deinterlace in a desktop editor and convert the progressive file. A hidden deinterlace here would blur progressive AVI that never needed that filter at all.
Will this work on iPhone or Android?: The converter runs in Safari and Chrome. Re-encoding is heavy, so a long AVI can overheat a phone or exhaust RAM. Prefer a computer for anything beyond a short clip..
Can I convert several AVI files at once?: Not currently. Each job keeps decoded frames in memory. Convert one, download the MP4, then drop the next. After the engine loads once, later files skip that download. A stack of holiday clips is still one conversion at a time.
Is it legal to convert AVI to MP4?: Re-encoding family camcorder files you recorded is the intended case. Re-encoding a commercial DivX you do not have rights to does not become lawful because the extension changed. Videozify does not store files and cannot check a licence.