Convert local video files without uploading
Media bytes stay in browser memory and are never sent to a conversion server.
Private FFmpeg.wasm conversion
Free Online Video Converter for MP4, WebM, MKV, MP3, and GIF
Choose a media file from this device and convert it locally with FFmpeg.wasm. Nothing is uploaded, stored, watermarked, or tied to an account.
No upload No signup No watermark
Open the tool Choose a local media file. It will not be uploaded.
Create MP4, WebM, MKV, MP3, or GIF output
Choose fast remuxing for compatible streams or re-encode to a selected output profile.
Reuse the browser FFmpeg engine for more files
The 31 MB core loads on demand and remains available for additional conversions in the same session.
How to convert a video file online without uploading it
Select or drop a local file, choose the output format and quality, then start conversion. The result is assembled in browser memory and downloaded from a temporary local object URL.
Private local processing is useful for short drafts and compatibility fixes. It also avoids waiting for an upload before work can begin.
When to use desktop FFmpeg instead of browser conversion
Use native FFmpeg for multi-gigabyte files, long 4K media, batch jobs, hardware acceleration, subtitle workflows, or complex filters.
The browser sandbox has memory and CPU limits. This page intentionally blocks files above about 1 GB rather than risking an unstable tab.
Common questions
Local Video Converter frequently asked questions
Straight answers about browser support, privacy, source access, and output behavior.
Are local video files uploaded during conversion?
No. The file is read into browser memory and passed to FFmpeg.wasm locally. There is no upload step or cloud storage.
Why is browser video conversion slower than desktop FFmpeg?
WebAssembly runs inside the browser sandbox and commonly uses fewer CPU resources than a native FFmpeg build. The first conversion also loads a 31 MB media engine that is reused for the rest of the session.
Which local media formats can I convert online?
Common MP4, MOV, MKV, WebM, AVI, MP3, AAC, and WAV inputs are supported when the bundled FFmpeg build contains the required decoder. Outputs include MP4, WebM, MKV, MP3, and GIF.
Will remuxing a video reduce quality?
No. Original-stream remux mode copies compatible encoded tracks without recompressing them. It is much faster, but a copied codec may still be unsupported by the target device.
How do I convert MKV to MP4 without losing quality?
Use Original quality mode. When the MKV contains H.264 video and AAC audio, remuxing copies those tracks into an MP4 container in seconds without any recompression. Re-encode only when the source codecs are not supported by your target device.