Why convert MP4 to WebM?

WebM files are smaller and optimized for web browsers. They're ideal for HTML5 video elements and web performance optimization.

Which codec is used for WebM?

WebM uses VP9 video codec and Opus audio codec, providing excellent quality at smaller file sizes than H.264.

Is WebM supported by all browsers?

WebM is supported by Chrome, Firefox, and Edge. Safari has limited support. For maximum compatibility, keep MP4 as fallback.

MP4 to WebM Offline Converter

Convert MP4 videos to WebM format completely offline in your browser

No Upload 100% Private Free

Loading Video Processing Engine

This tool uses FFmpeg.wasm for video processing. The first time you use it, it will download the processing engine (~25MB). This only happens once and enables powerful offline video conversion.

Initializing video processor...

Drop your MP4 videos here

or click to select MP4 files

Conversion Settings

Video Quality

Output Resolution

VP9 encoding for WebM is slower than H.264. VP9 uses constant quality rate (CRF) mode for best results.

Optimized for Web Video

Web Optimized

WebM with VP9 is ideal for HTML5 video elements and web performance optimization.

Smaller Files

VP9 codec produces smaller file sizes than H.264 at equivalent visual quality.

100% Private

All processing happens locally in your browser. Your videos never leave your device.

WebM Browser Support

Chrome - Full Support

Firefox - Full Support

Edge - Full Support

Safari - Limited

Android - Full Support

iOS Safari - Limited

HTML5 Video Tag

Web Apps

Tip: For maximum compatibility, keep your original MP4 as a fallback alongside the WebM version.