Video Converter: Free Online MP4, WebM & GIF Converter, No Upload

How the conversion works

When you drop in a file, the tool writes it into an in-memory filesystem that FFmpeg can read directly, then runs an encoding command tuned for the format you picked. MP4, MOV, and MKV outputs use the H.264 codec at a constant quality setting (CRF 23), which balances file size against visible quality for most footage. WebM uses VP9 and Opus instead, both open codecs built for the web, and typically produces a smaller file than MP4 at a comparable quality level. Audio-only outputs strip the video stream entirely with the -vn flag before encoding just the sound. None of this touches a server: the FFmpeg binary itself runs as WebAssembly inside your tab, so the encoding math happens on your CPU the same way it would if you had FFmpeg installed as a desktop app.

Supported output formats

Choosing the right format

Pick MP4 when you need something that opens everywhere without a second thought: phones, TVs, video editors, and every major platform accept it. Choose WebM if the file is headed for a website and you want a smaller footprint at similar quality. MOV suits an Apple-based editing workflow, while MKV earns its place when you need to preserve extra audio tracks or subtitle streams in one container. Reach for GIF only for short, silent, low-resolution clips, since the 30-second and 480-pixel caps exist to keep the output file from ballooning. If you only need the sound, MP3 covers nearly every use case, and WAV is there for the rare situation where you cannot afford any quality loss at all.

Converting multiple files at once

The Batch tab applies one chosen format to every file you drop in, then processes them one at a time so your browser tab does not run out of memory trying to hold several encodes in flight simultaneously. Each file gets its own progress bar and its own download link once it finishes, and you can remove a queued file before processing starts if you added the wrong one. A failed file shows its error message inline without stopping the rest of the queue.

Tips for smoother conversions

• •Keep files under 500 MB where you can. Conversion time scales with both file size and your device's CPU speed, and very large files can push against your browser's available memory.
• •Leave the tab open and active while a job runs. Switching away or closing the tab interrupts the FFmpeg worker mid-encode.
• •Trim a clip down first with a dedicated clipper if you only need part of a long video. Smaller input means a faster conversion.
• •The engine downloads roughly 32 MB the first time you use it, then your browser caches it, so the second conversion in a session starts immediately.

Privacy and local processing

Because encoding happens on your device, this tool has no upload step, no storage bucket holding your footage, and no server-side log of what you converted. There is nothing to delete afterward because nothing was ever sent anywhere. The only network activity is the one-time download of the FFmpeg engine itself, which contains no tracking and reads none of your files.