Overview
Re-encodes a video in your browser to WebM with VP9 or VP8, or to MP4 where the browser can record it, so you can shrink it, change resolution or switch formats without uploading. Choose resolution, frame rate and quality or an exact bitrate, trim the start and end, keep or drop audio, and compare the size before and after.
How It Works
Drop a video the browser can play. The tool reads its resolution and length and lists the output formats this browser supports, greying out the rest. Pick a format, a resolution from 240p up to the original, a frame rate and a quality level, or type a bitrate in kbps. Trim with the sliders and the panel shows the output size, bitrate and an estimated file size. Click Convert; the clip plays silently while it is recorded, and the result appears with a player and a download button.
Step-by-Step Usage Guide
- Drop the video you want to compress or convert.
- Choose an output format that this browser supports.
- Pick a resolution, frame rate and quality or bitrate.
- Trim the start and end if you only need part of the video.
- Click Convert, keep the tab open, then download the result.
Technical Specifications & Standards
Browsers expose video encoders through MediaRecorder, and that is what this tool uses. The source plays in a hidden video element, each frame is drawn onto a canvas scaled to the chosen size, and the canvas capture stream is recorded at your frame rate and bitrate. Audio is routed from the element through the Web Audio API into the same stream without reaching your speakers. Because MediaRecorder works in real time, a 3-minute clip takes about 3 minutes, and keeping the tab visible matters, since background tabs throttle drawing. The format list comes from MediaRecorder.isTypeSupported. Chrome, Edge and Firefox record WebM with VP8 or VP9 and Opus, Chrome 126 and later can also record MP4, and Safari records MP4 with H.264 and AAC. Automatic bitrates scale with pixels per second, from about 0.05 bits per pixel for small files to 0.15 for high quality, and resolutions are rounded to even numbers as encoders require. WebM files from MediaRecorder lack a duration field, so some players show the length only after playing.
Targeted Use Cases
- Shrinking a phone video so it fits under an email or chat attachment limit.
- Converting an MP4 to WebM for a website video background.
- Lowering a 4K recording to 720p for a quick review link.
- Cutting the first and last seconds off a clip while re-encoding.
- Removing the audio track from a screen recording.
Notes & Gotchas
- Pick 720p with the Balanced setting for most sharing; it usually cuts size a lot with little visible loss.
- Choose VP9 over VP8 when available, as it is smaller at the same quality.
- Leave the tab in front and the device plugged in for long conversions.
- Check the estimated size before converting and lower the bitrate if it is still too big.
Frequently Asked Questions
Why does conversion take as long as the video?
Browsers only offer video encoding through MediaRecorder, which records a stream as it plays. The tool plays your clip silently at normal speed and records it, so encoding time equals clip length.
Why is MP4 not available?
Your browser cannot record MP4. Safari and Chrome 126 or later can; Firefox and older Chrome builds record WebM only. The list shows exactly what this browser's MediaRecorder reports as supported.
Can it make the file bigger instead of smaller?
Yes, if the bitrate is higher than the source's. Phone videos are often already efficient, so choose a lower resolution or the Small file setting, and compare the before and after sizes shown.
Is my video uploaded to a server?
No. Decoding, scaling and encoding all happen in your browser. That is why it is limited to the formats your browser can record, and why it works with no internet connection after the page loads.
Why can my player not show the length of the WebM?
MediaRecorder writes WebM as a live stream and leaves out the duration field. Chrome, Firefox and VLC still play and seek it; some other players show the length only after reaching the end.
Related tools
- Extract Audio from Video - Pull the audio track out of an MP4, WebM or MOV video and save it as lossless WAV (16 or 24-bit) or as compact Opus where supported. Optional mono mixdown. Decoded locally, never uploaded.
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- Audio Trimmer & Converter - Cut audio on a waveform, add fade in and fade out, normalise the peak, change speed or mix to mono, then export WAV (16, 24 or 32-bit float) or Opus. Preview the result before saving.
- Camera & Screen Recorder - Record your webcam, screen, or both with webcam picture-in-picture — configurable resolution and audio, saved as MP4 or WebM locally. No uploads.
- Online Video Editor (Timeline, Trim, Text & Music) - Edit video in your browser on a multi-track timeline: trim, split, speed, fades, filters, transitions, titles, logos and music, then export WebM or a WAV mix. Files never leave your device.
- Image Compressor - Shrink JPEG and WebP file sizes with a quality slider and optional max-width. Preview the result and see exactly how many percent you saved.