Is my video uploaded anywhere?

No. The conversion runs with ffmpeg compiled to WebAssembly directly in this browser tab — the file is read locally and never transmitted to a server.

How big a file can I convert, and will it be slow on a phone?

Browser memory is the real limit, roughly 2 GB in a tab, so very long 4K footage may fail on lower-end devices. Desktop browsers with more RAM handle multi-minute clips comfortably; on a phone, keep clips shorter or lower the resolution first for reasonable speed.

Which codecs are actually available?

This build ships H.264 (libx264), VP8 and VP9 (libvpx) for video, and AAC, MP3, Opus, Vorbis and FLAC for audio — no HEVC/H.265 or AV1, since those aren't in the default WebAssembly core.

Why is conversion slower than desktop software?

ffmpeg.wasm runs single-threaded in WebAssembly rather than using native hardware encoders, so it trades some speed for running with zero installs and zero uploads.

Can I add a watermark or burn in subtitles?

Yes — the advanced panel supports a text or image watermark with position and opacity, plus SRT subtitle burn-in with adjustable font size and colour.

ToolMano

Video converter & compressor

Convert, resize and compress video between MP4, WebM, MKV, MOV and AVI.

No uploadNo signupWorks offline

Drop files here or click to choose

MP4, WebM, MKV, MOV or AVI · converted in your browser

Up to 20 MB

Output container

Video codecOnly codecs this WebAssembly build actually supports

Quality (CRF, lower = better) — 23

Resolution

Quick presets

Choose a video above to start.

Idle — nothing is uploaded, everything runs on this device.

Runs fully in this browser tab via WebAssembly — nothing is uploaded. Very large files are limited by your device's memory, roughly 2 GB in a browser tab, so trim long recordings first if you hit an out-of-memory error.

10 of 10 runs left today on the no-signup plan. Get more with a free account

About video converter & compressor

Video converter & compressor re-encodes video between MP4, WebM, MKV, MOV and AVI, with full control over codec, quality, resolution, frame rate, crop, rotation, colour, watermarks and audio track — all with live progress as ffmpeg.wasm runs.

Everything happens with the WebAssembly build of ffmpeg loaded straight into this page, so raw footage never leaves your device. That matters for family videos, unreleased edits or anything under an NDA.

Presets get you to a smaller file fast; the advanced panel exposes close to a hundred real ffmpeg options for people who want to dial in bitrate mode, GOP size, subtitles or a watermark precisely.

How to use Video converter & compressor

1Drop in a video file (MP4, WebM, MKV, MOV or AVI).
2Pick an output container and codec, or start from a resolution preset.
3Adjust quality, trimming, filters or watermark in Advanced mode if needed.
4Press Convert and download the result once processing finishes in your browser.

What it does

H.264, VP8 and VP9 encoding with CRF or bitrate control
Resolution presets from 4K down to 360p plus custom scaling
Trim, speed change, deinterlace and frame-rate conversion
Colour correction: brightness, contrast, saturation, gamma, hue
Text and image watermarking with position and opacity control
Subtitle burn-in from an SRT file
Audio re-encode, volume, loudness normalisation or full mute
Runs entirely offline in the browser tab via WebAssembly

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