Convert AVI to MP4 Online

Convert AVI to MP4 online for a video you can share, upload, and play more easily. Use the browser tool for a quick file, or UniConverter Desktop on Windows and Mac for a folder of recordings and more control over video settings.

Create a compatible local copy:

Add your AVI video
Choose MP4 and suitable settings
Convert, save, and check playback

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Quick Answer

To convert AVI to MP4, add your .avi video, choose MP4, convert it, and save the result.
For broad playback compatibility, select H.264 video with AAC audio when those settings are available.
Keep the source resolution and frame rate unless you need a smaller delivery copy.
Renaming .avi to .mp4 does not convert the file.

How to Convert AVI to MP4

Step 1

Add your AVI video

Upload the .avi file in the converter above. Play the source first if possible: an AVI container may use an older codec, and a recording that is already damaged may need repair before conversion. For a desktop batch, add the local recordings to UniConverter.

Step 2

Choose MP4 and suitable settings

Select MP4 as the output. Online conversion offers a quick browser workflow; for codec, resolution, bitrate, or frame-rate choices, use the available desktop output settings. H.264 and AAC are a practical combination for many phones, browsers, and editing applications.

Step 3

Convert, save, and check playback

Run the conversion and download the MP4. Check the beginning, middle, and end for sound, sync, and smooth motion. Retain the AVI original until the MP4 plays in the application or on the device you actually need.

Convert AVI to MP4 with UniConverter Desktop

Use a local conversion queue for supported files, then review the exported copy before sharing.

See the official video conversion guide.

Add your local recordings

Open UniConverter Desktop, select Converter, and use Add Files to import the AVI recordings.

Add video files or a folder in UniConverter 18 Converter. Official desktop guide illustration.

Choose the MP4 output

Choose MP4 in Convert to. For broad compatibility, use H.264 video and AAC audio. Match source resolution and frame rate unless your destination needs something different.

Choose a video output profile in UniConverter 18 Converter. Official desktop guide illustration.

Convert and review

Choose Save to, run Convert All, and check duration, seeking, audio and sync in the intended player.

Review converted files in the Finished tab. Official desktop guide illustration.

Before you finish: compare the result with the source, check the actual dimensions and file size, and open it in the application where it will be used. Keep the original until these checks pass.

AVI vs MP4: What Changes?

What to compare	AVI	MP4
Extension	.avi	.mp4
Format type	Audio Video Interleave media container	MPEG-4 Part 14 media container
Video codecs	Varies; older files may use DivX, Xvid, or MJPEG	Varies; H.264 is a common compatibility choice
Audio	Depends on the streams in the AVI	AAC is common; compatibility depends on the player
Typical use	Older recordings, camera exports, legacy software	Playback, web uploads, sharing, and device delivery
Quality	Depends on the original codec and settings	Re-encoding can lose detail; the container adds none
File size	Not inherently large or uncompressed	Not guaranteed smaller; codec and bitrate matter
Keep as master	Keep an original recording for future work	Use the converted copy for the target workflow

References: UniConverter video conversion guide · Supported desktop formats

Practical Tips for AVI to MP4

Online AVI to MP4 conversion

Turn an occasional AVI recording into an MP4 in your browser. Follow the file-size and conversion allowance displayed in the tool. A free online task is useful for quick sharing; it does not make the desktop software or every conversion option unlimited.

Output for everyday playback

MP4 is a container, so choosing the right streams matters. H.264 video and AAC audio often work well for sharing with colleagues, uploading to websites, and watching on phones. An MP4 containing an unsupported codec can still fail to play.

Keep the detail that matters

Match the source dimensions and frame rate when your priority is a faithful copy. Increasing resolution will not recover detail missing from the AVI. Avoid repeatedly encoding the same video; make a new delivery copy from the original instead.

Batch AVI files on desktop

Use UniConverter Desktop when you have a collection of camera clips or legacy recordings. Add files to one conversion queue, select an MP4 output, and choose a destination folder. Check one representative result before converting the rest.

Balance bitrate and file size

Reducing video bitrate can make a smaller MP4, but aggressive compression creates blocking and soft edges. Use an appropriate resolution for the destination and keep enough bitrate for movement. Shortening unwanted footage is another way to reduce the delivery size.

Check older recordings carefully

AVI files can contain unusual audio, interlaced footage, or variable timing. If the output is silent, inspect the source audio and selected track. If motion has comb-like edges, an interlaced source may need deinterlacing in a suitable video workflow.

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AVI to MP4 FAQs

How do I convert AVI to MP4 online for free?

Add an AVI file to the online converter, choose MP4, run the conversion, and save the output. Use the allowance shown in the widget. For a large folder or more output settings, use the desktop converter; its trial and paid features have separate terms.

Is AVI a video codec or a file format?

AVI stands for Audio Video Interleave. It is a container that can hold video and audio encoded with different codecs. A player needs support for the streams inside it, so two .avi files can behave differently even though their extensions match.

What program should I use for high-quality AVI to MP4 conversion?

Choose a converter with the settings your task needs. UniConverter provides a desktop interface for conversion and batches; HandBrake is a free transcoding option, and FFmpeg offers command-line control. Source quality, codec, resolution, and bitrate matter more than a promise of lossless conversion.

Can I convert AVI to MP4 without losing quality?

Re-encoding video can reduce quality. A compatible stream-copy or remux workflow avoids re-encoding, but not every codec found in AVI works in MP4 or in the target player. For broad compatibility, an H.264/AAC conversion may be preferable even though it re-encodes.

Will an AVI to MP4 converter make my video smaller?

It can, particularly when an older or less efficient source is encoded with suitable settings. The result is not guaranteed to be smaller. Duration, resolution, frame rate, audio settings, and video bitrate all affect the final size.

Why does my converted MP4 have no sound?

First confirm that the AVI has an audible audio track. Then check the selected track, volume, and output audio codec. AAC is a useful compatibility choice. Test the MP4 in a second player before assuming the converter removed the sound.

Can I change the extension from AVI to MP4?

Changing the filename only changes the label. It does not rewrite the container or encode the streams. Use an AVI to MP4 converter and keep the original until the exported MP4 opens correctly.

Can I batch convert AVI to MP4 on Windows or Mac?

Yes. Add multiple local videos in UniConverter Desktop, choose MP4, set the output folder, and run the queue. Review a test clip first, especially when your folder mixes different cameras, dimensions, or codecs.

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Supported desktop formats