Are files uploaded during browser conversion?
No. The selected file is copied into the browser's local WebAssembly memory and is not posted to VLC.ONL. Closing the page clears that working session.
Free Browser Video Converter for Local Files
Convert MKV, AVI, MOV, MP4, WebM and common audio files without uploading the source. Choose a fixed output preset, run FFmpeg in this browser, and download a separate converted file.
Convert one file on this device
The 31 MB conversion engine loads only when conversion starts. Input bytes stay in browser memory and are not posted to VLC.ONL.
Browser-local processingNo media upload endpoint
Your selected file is not uploaded to the VLC.ONL server.
- Source file
- Browser type
- File size
MP4 compatibility preset
Creates H.264 video with AAC audio for broad playback support. Conversion cannot add detail missing from the source.
Preparing the local engine0%
Waiting for a file.
Your converted file is ready
The original file remains unchanged.
Choose an output for the next device or task
A container is not a quality setting. MP4 is the broadest general-purpose choice, WebM fits modern web delivery, AVI targets older workflows, and audio presets remove the picture.
| Output | Encoded streams | Useful when | Important limit |
|---|---|---|---|
| MP4 | H.264 + AAC | You need broad phone, computer and television compatibility | Re-encoding takes time and can reduce quality |
| AVI | MPEG-4 + MP3 | An older editor or device explicitly requires AVI | AVI is not the best default for modern delivery |
| WebM | VP9 + Opus | You need an open format for modern browsers | Older hardware may not support VP9 |
| MP3 or AAC | Lossy audio | You need a smaller audio-only copy | Removed video cannot be restored from the output |
| FLAC or WAV | Lossless audio | You need editing or archival audio without added lossy compression | Files are much larger than MP3 or AAC |
What conversion changes
Transcoding writes new streams
MP4, AVI and WebM conversion decodes the source and encodes new video and audio streams. The result may play on more devices, but it cannot improve the detail already present in the source.
Remuxing changes only the container
The fast MP4 option first checks the browser engine's stream report. It copies H.264 video with compatible AAC or MP3 audio. Other combinations automatically use the regular MP4 transcode preset.
When to use another VLC.ONL path
Edit instead of converting
Use the browser video editor when you need trimming, reframing, picture adjustments or a title.
Diagnose before rewriting
Read the containers and codecs guide when one file fails in VLC. For desktop conversion with more control, follow the VLC Convert/Save workflow.
Continue with the finished file
Upload and share the finished video with a temporary link, use the VLC subtitle directory when it needs a separate text track, or return to all free video tools.
Open-source engine and source availability
This tool uses the single-threaded @ffmpeg/ffmpeg 0.12.15 wrapper and @ffmpeg/core 0.12.10. The wrapper is MIT-licensed and the WebAssembly core is GPL-2.0-or-later. Runtime files are pinned and checksum recorded.
Browser video converter questions
These answers cover the decisions that most often change the correct next step.
Can converting a video improve its quality?
No. Conversion can make streams compatible with another container or device, but it cannot recreate detail missing from the source. Re-encoding may reduce quality.
What is the difference between transcoding and remuxing?
Transcoding decodes and encodes new streams. Remuxing copies compatible streams into a new container. The fast MP4 option checks for H.264 video with AAC or MP3 audio before copying.
Why is browser conversion slower than desktop FFmpeg?
The converter uses a single-threaded WebAssembly build inside browser limits. Large or long videos usually convert faster in VLC or a desktop FFmpeg installation.