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How to convert AVI to MP4 on a Mac
By Himanshu Ranjan · Updated 8 November 2026
AVI is a 1992 Microsoft container that modern Apple apps often refuse to play. To convert AVI to MP4 on a Mac, select the file in Finder and run FileDial's Convert › Convert to MP4. You get a new MP4 beside the original, made offline, with nothing uploaded and the AVI kept.
Why old AVI files will not open
AVI, short for Audio Video Interleave, was introduced by Microsoft on 10 November 1992 as part of Video for Windows. It predates most of what we expect from video today. Wikipedia notes that the original specification has no standard way to record aspect ratio, was not designed for compression that uses B-frames, and cannot hold attachments such as subtitles.
In practice, old camcorder clips, downloaded files and archived family video arrive as AVI. QuickTime Player may refuse the file or play it with the wrong shape or no sound, because the codec inside is one macOS does not read.
Convert it with FileDial
The conversion is one tool and works on one file or many.
- Select the AVI file or files in Finder.
- Hold the right Option key to open the dial.
- Choose Convert › Convert to MP4.
- Check the new MP4, which is saved beside the AVI, plays correctly in QuickTime Player.
Check the result before deleting anything
Play the MP4 from start to end and look at three things: the picture shape, whether audio stays in sync and whether the whole length is there. If you notice interlaced lines, a comb-like effect on moving edges common in older camera footage, run Adjust › Deinterlace on the result. If the clip is too dark, Adjust › Brightness, contrast & saturation… can help.
Keep the AVI until you are satisfied. Disk space is cheap compared with a family video you cannot recover.
Alternatives on macOS
VLC and similar players can open many AVI files directly, which is the simplest option if you only need to watch. QuickTime Player on current macOS does not reliably play legacy AVI codecs, so you cannot count on it. For editing in iMovie or sharing to a phone, converting to MP4 is the dependable route.
If you want a smaller file after converting, FileDial's Compress tools run on the new MP4. See the compress-video guide for the options.
Digitised tapes and old downloads
Many AVI files on a Mac are digitised camcorder tapes, clips from old digital cameras or downloads from years ago. They tend to be low resolution and sometimes interlaced, so expect a modest picture even after conversion. Converting does not add detail, but it makes the footage playable and editable in current tools.
Check dates and names while you are at it. FileDial's Rename › Add date prefix puts a creation date in front of file names, which keeps a converted archive in order, though it renames the originals, so use it deliberately.
Organising the converted files
Put the MP4 copies in a new folder and keep the AVIs in a separate archive until you are sure everything converted well. Batch › Checksums (SHA-256) writes a text file of checksums, which lets you confirm later that a backup copy has not changed.
If you want the footage on a phone, MP4 works with AirDrop and Photos. If it is for a family member's older TV, check the TV supports MP4 and the codec inside.
Settings, size and what to expect
AVI files from the early 2000s are often small in pixels, sometimes 640 by 480 or lower, so the MP4 will also be small. Converting will not sharpen them, and enlarging them afterwards only makes soft pictures bigger. If you want to watch them full screen, accept some softness.
File size can move either way. Old AVI files used less efficient codecs, so the MP4 may be smaller, but a conversion that re-encodes can also make a larger file than you expect. Read the size on the result card rather than assuming. If the MP4 is too large, run a Compress tool on it. If you plan to keep an archive for years, convert once and avoid repeated re-encoding, because each generation loses a little quality.
Wikipedia also notes that AVI cannot hold subtitles, so any subtitles for an AVI live in a separate file that you should keep next to the MP4. FileDial is the right tool for a quick, private conversion. For a rescue of a damaged file or unusual codec, a specialist tool may succeed where a general converter fails.
Do not upload old family video
Old AVI collections often hold personal footage. Free web converters need the whole file uploaded, and the FBI has warned that free online converters are increasingly used to spread malware. A local conversion keeps the footage on your Mac.
Questions
Why does my AVI file not play on a Mac?
AVI is only a container, and the video inside may use a codec macOS does not read. QuickTime Player often fails on older AVI files. Converting to MP4 with Convert › Convert to MP4 produces a file Apple apps can open. Many old AVI files use codecs that macOS no longer includes, which is why even a working file can fail to open.
Is AVI to MP4 conversion lossless?
Not necessarily. A conversion may re-encode the video, which can reduce quality slightly. Keep the original AVI until you have confirmed the MP4 looks and sounds right from start to finish. Compare the length and sound of the MP4 with the original before deleting anything, because quality issues show up on playback.
What if the video looks striped when it moves?
That is interlacing, common in older footage. Run Adjust › Deinterlace on the converted file to get a copy without the comb effect. Your original stays unchanged. Interlacing was common in tape-era footage, and deinterlacing makes a separate copy, so you can compare both.
Can FileDial convert a folder of AVI files?
Yes. Select all the files in Finder and run Convert › Convert to MP4 once. Each file gets its own MP4 beside the original, so the originals are never overwritten. Selecting a whole folder works well, and the originals are never overwritten, so you can compare each pair.