WebM is an open-source video format developed by Google in 2010, optimised for web delivery. It's used extensively for HTML5 video, YouTube playback in Chrome, browser-based screen recordings, and videos exported from Google services like Slides and Canva. The problem: WebM doesn't play on iPhones, doesn't work in most Smart TVs' native media players, and is rejected by many social media platforms and video editors. Converting to MP4 instantly resolves all of these compatibility issues.
How You End Up With WebM Files
WebM files appear in several common workflows:
- Downloading video from YouTube using a browser extension (YouTube often serves WebM in Chrome)
- Screen recording on Linux — GNOME Recorder, SimpleScreenRecorder, and OBS default to WebM
- Screen recording in Chrome OS (Chromebook recordings are WebM by default)
- Exporting video clips from Google Slides or Canva
- Downloading video from Twitter/X using a downloader tool
- Receiving a WebM file from a developer or colleague on Linux
- Downloading video from a website that streams VP9 WebM content
Where WebM Fails
WebM just doesn't work in a lot of places:
- iPhone and iPad — iOS does not support WebM in any built-in app
- Smart TVs (most Samsung, LG, Sony models) — native media players reject WebM
- WhatsApp, Instagram, and TikTok — reject WebM video uploads
- Windows Media Player — does not support WebM without codec installation
- iMovie, Final Cut Pro, Premiere on Mac — limited WebM support
- PowerPoint and Keynote — cannot embed WebM video files
How to Convert WebM to MP4 Free
Go to convifi.com/convert/webm-to-mp4, drop your file, and it converts right in the browser:
- Go to convifi.com/convert/webm-to-mp4
- Drag and drop your WebM file or click to browse
- Choose a quality preset — Balanced is usually sufficient for most purposes
- The conversion runs locally in your browser using WebAssembly
- Download the MP4 when it's done
WebM Codecs: VP8, VP9, and AV1
WebM can contain different video codecs depending on its source. VP8 is the older codec (used in early WebM files). VP9 is the modern standard used by YouTube for high-quality streams. AV1 is the newest codec, offering excellent compression but slow encoding. When converting to MP4, all three can be re-encoded to H.264 or H.265. The quality difference between VP9 and H.264 at equivalent bitrates is minimal for most content.
Will Quality Be Lost?
Converting WebM to MP4 involves re-encoding the video, which introduces some quality loss. At high quality settings, this loss is imperceptible — the difference is statistically present but visually invisible. At low quality settings, you'll see compression artifacts. For screen recordings (which contain text and UI elements), always use a high quality preset — text in videos is the first thing to look degraded by compression. For casual video content, Balanced quality is fine.
File Size After Conversion
WebM and MP4 at equivalent quality settings are very similar in file size. VP9 WebM is sometimes slightly more efficient than H.264 MP4. If you convert and notice the MP4 is somewhat larger than the original WebM, that's normal — you're trading a marginal size increase for massively better device compatibility. If you need to reduce file size, lower the quality setting slightly.
Converting WebM Screen Recordings
Screen recordings in WebM often look blocky or have compression artifacts when converting. This happens because screen recordings were often saved at a low bitrate to keep file sizes manageable. The solution: when recording, always use a high bitrate or lossless codec setting. If your WebM recording already has artifacts, converting to MP4 won't remove them — those are baked into the source file.