How to convert WebM to MP4 without losing quality
Three free ways to turn a WebM into an MP4 that plays everywhere — and why downloading the MP4 in the first place is usually better.
3 min read · Updated
WebM files are efficient, but iPhones, QuickTime, many TVs and most editing apps won't open them. Converting to MP4 fixes that. How much quality you lose depends on how you convert — and sometimes you don't need to convert at all.
First: can you skip converting?
If the video is still online, the cleanest fix is to download it again as MP4. A converted file is a copy of a copy: the WebM was already compressed once, and converting compresses it a second time. The MP4 version from the source has been compressed only once.
On the YouTube downloader, each option shows its format. If you need MP4 for an editor, a presentation or an iPhone, pick an MP4 option at the resolution you want.
Why converting loses a little quality
WebM usually holds VP9 or AV1 video with Opus audio; MP4 for maximum compatibility holds H.264 video with AAC audio. Changing codecs means decoding every frame and compressing it again, and each compression discards some detail.
At a high quality setting the loss is very hard to see. It becomes visible when the setting is too low, or when a file is converted repeatedly. Convert once, from the best file you have.
Option 1: HandBrake (Windows, Mac, Linux)
HandBrake is a free, open-source converter with sensible presets:
- Open HandBrake and drag in the WebM file.
- Choose a preset that matches the resolution, such as Fast 1080p30 (or a higher-quality “HQ” preset).
- Under Summary, set Format to MP4. Under Video, the H.264 encoder gives the widest compatibility.
- Choose where to save, then click Start Encode.
If a preset's frame rate or resolution doesn't match your source, set them to “Same as source” so nothing is changed unnecessarily.
Option 2: VLC (every platform)
VLC can convert as well as play:
- Open VLC and choose Media › Convert / Save (on a Mac: File › Convert / Stream).
- Add the WebM file and click Convert / Save.
- Pick the profile “Video – H.264 + MP3 (MP4)” or a similar H.264 MP4 profile.
- Choose a destination file ending in .mp4 and start.
VLC's defaults aim for speed rather than maximum quality. For something you'll keep, HandBrake or FFmpeg give more control.
Option 3: FFmpeg (command line)
FFmpeg is the engine behind many converters. This command re-encodes to H.264 and AAC at a high quality setting:
ffmpeg -i input.webm -c:v libx264 -crf 18 -preset slow -c:a aac -b:a 192k output.mp4
Lower -crf values mean higher quality and bigger files; 18–22 is a good range. -preset slow compresses more efficiently than the default at the cost of time.
Remuxing: the no-loss shortcut that rarely works for WebM
Remuxing moves the existing streams into a new container without re-encoding, so nothing is lost. It only produces a widely playable file when the codecs inside are already MP4-friendly — H.264 or H.265 with AAC audio. WebM files almost always carry VP9 or AV1 with Opus, so remuxing them to .mp4 gives a file that many of the same devices still can't play. For WebM, re-encoding is usually the honest answer. H.264 vs H.265 vs AV1 explains why.