---
title: "How to convert a video to MP4 | ToolSugar"
description: "Convert MOV, WebM, MKV or AVI to MP4 in your browser, and see why some files finish in seconds while others take minutes."
canonical: https://toolsugar.com/blog/how-to-convert-a-video-to-mp4
image: https://toolsugar.com/og.png
---

# How to convert MOV, MKV or WebM to MP4

Updated 2026-11-09

To convert a video to MP4, move its picture and sound into an MP4 file, and re-encode them only if the format does not fit. Convert to MP4 does this in your browser. It reads the codecs first, then tells you whether it copied or re-encoded. MOV and MKV files with H.264 video copy in seconds.

[Open Convert to MP4](https://toolsugar.com/tools/video-converter)

## Convert a video to MP4 in four steps

The tool takes MOV, WebM, MKV, AVI, M4V and most other video files.

1. Choose a MOV, WebM, MKV, AVI or M4V file.
2. Leave the method on Copy when possible, unless a player rejects the result.
3. Press Convert to MP4 and keep the tab open.
4. Read what was copied or re-encoded, then download the MP4.

## Copy or re-encode: what actually happens

MOV, MKV and MP4 are containers, like boxes. The video and audio inside are separate things. When the video is H.264 and the audio is AAC or MP3, the tool lifts them out of one box and places them in an MP4 box. Nothing is decoded, so the picture is unchanged.

VP9 or HEVC video, or Opus audio, cannot go into this MP4 as they are. Those streams are re-encoded to H.264 and AAC. That takes far longer and costs a small amount of detail.

## File size limits for each path

A copy handles files up to 500 MB on a computer and 250 MB on a phone, because it only moves data. A re-encode is limited to 120 MB on a computer and 60 MB on a phone, because the browser has to decode every frame.

## What is left out

The MP4 keeps the first video track and the first audio track. Subtitles and extra language tracks are dropped. If you need a second audio language, convert with a tool that keeps every track.

## When the MP4 still will not play

Some strict players reject a copied file, for example when the source is 10 bit video or uses an unusual H.264 profile. Switch the method to Always re-encode. It rebuilds the video as standard 8 bit H.264, which plays on nearly every device.

## Questions

### How do I convert MKV to MP4 without losing quality?

Leave the method on Copy. If the MKV holds H.264 video and AAC or MP3 audio, the streams move across unchanged and the result states that it was a copy.

### Will the MP4 be smaller than the original?

About the same size after a copy, because the same data is stored. To shrink it, run the MP4 through Compress Video afterwards.

### Does the conversion upload my file?

No. The work happens in your browser tab from a copy of the file in memory, and the page does not send the video to a server.

[Open Convert to MP4](https://toolsugar.com/tools/video-converter)

## Related guides

- [How to compress a video without losing quality](https://toolsugar.com/blog/how-to-compress-a-video)
- [How to trim a video without re-encoding](https://toolsugar.com/blog/how-to-trim-a-video)
- [How to remove audio from a video](https://toolsugar.com/blog/how-to-remove-audio-from-a-video)
- [How to extract audio from a video](https://toolsugar.com/blog/how-to-extract-audio-from-a-video)

## Comparisons

- [Clideo alternative](https://toolsugar.com/alternatives/clideo-alternative)
- [CloudConvert alternative](https://toolsugar.com/alternatives/cloudconvert-alternative)
- [Convertio alternative](https://toolsugar.com/alternatives/convertio-alternative)
- [FreeConvert alternative](https://toolsugar.com/alternatives/freeconvert-alternative)