Why does the first audio or video tool take a moment to start?

Because it downloads FFmpeg. These tools run the open-source FFmpeg engine compiled to WebAssembly — a 32 MB file, roughly 10 MB once your connection compresses it — which arrives once, is cached by the browser, and then runs entirely on your device. Every tool you open afterwards starts immediately.

Are my videos uploaded for conversion?

No. That download is the converter itself coming to your file, instead of your file being sent to a converter. The video never leaves the tab.

Which audio and video formats are supported?

MP4, MOV, WebM and GIF on the video side, and MP3, WAV and M4A on the audio side, including conversions between the two — for example pulling an MP3 out of an MP4.

Is browser conversion slower than a desktop app?

Usually yes, on a long video. FFmpeg in WebAssembly runs slower than the native build and gets one browser tab's worth of memory. For short clips and audio extraction the difference is small, and nothing gets uploaded or queued behind other people's jobs.

Audio & Video Tools

Convert, compress and trim video and audio right in your browser. These tools run the open-source FFmpeg engine compiled to WebAssembly — the first tool you open downloads it once (a 32 MB file, roughly 10 MB compressed in transit), and after that it loads from your browser cache. Your media files are never uploaded.

Video

MP4 to MP3

Extract the audio track from an MP4 video as an MP3 file — entirely in your browser with the FFmpeg engine.

MP4 to GIF

Turn a video clip into an animated GIF with adjustable frame rate and width, using a two-pass palette for the best colors.

GIF to MP4

Convert animated GIFs into small, smooth MP4 videos that autoplay everywhere and are usually dramatically smaller.

MOV to MP4

Convert QuickTime MOV videos — including iPhone recordings — into MP4 files that play everywhere.

WebM to MP4

Convert WebM videos (VP8/VP9) into H.264 MP4 files that play on Apple devices and everywhere else.

MP4 to WebM

Convert MP4 videos into open-format WebM (VP8/Vorbis) files for royalty-free web embedding.

Compress Video

Shrink MP4, MOV and WebM videos with a quality you choose, plus an optional 720p cap — with honest before/after sizes.

Video Trimmer

Cut a clip out of a video with a live preview — frame-exact re-encode or instant lossless keyframe copy.

Add Audio to Video

Put a music or voice track into an MP4 without re-encoding the picture — the browser equivalent of ffmpeg -c copy.

Audio

Compress Audio

Shrink MP3, WAV, M4A, OGG and FLAC files to a bitrate you choose, with honest before/after sizes.

WAV to MP3

Convert uncompressed WAV recordings into small, universal MP3 files at the bitrate you choose.

MP3 to WAV

Convert MP3 files into standard 16-bit PCM WAV files for editors, samplers and burning software.

M4A to MP3

Convert M4A/AAC audio — iPhone voice memos, iTunes tracks — into MP3 files that play absolutely everywhere.

Guides

MP4 to GIF with FFmpeg

The one-line command bands your colours. Here is the two-pass fix, and what it measures.

Add audio to a video with FFmpeg

The command everyone copies keeps the wrong audio. Here is what it does, measured, and the fix.

Honest limits: files are capped at 100 MB, encoding runs on a single browser thread so long videos take minutes, and phones with little free memory may struggle with large files. Every job shows real progress and can be cancelled at any point.

Frequently asked questions

Why does the first audio or video tool take a moment to start?: Because it downloads FFmpeg. These tools run the open-source FFmpeg engine compiled to WebAssembly — a 32 MB file, roughly 10 MB once your connection compresses it — which arrives once, is cached by the browser, and then runs entirely on your device. Every tool you open afterwards starts immediately.
Are my videos uploaded for conversion?: No. That download is the converter itself coming to your file, instead of your file being sent to a converter. The video never leaves the tab.
Which audio and video formats are supported?: MP4, MOV, WebM and GIF on the video side, and MP3, WAV and M4A on the audio side, including conversions between the two — for example pulling an MP3 out of an MP4.
Is browser conversion slower than a desktop app?: Usually yes, on a long video. FFmpeg in WebAssembly runs slower than the native build and gets one browser tab's worth of memory. For short clips and audio extraction the difference is small, and nothing gets uploaded or queued behind other people's jobs.