About Transcodr
Transcodr is a free, general-purpose media converter that runs real ffmpeg compiled to WebAssembly — entirely inside your browser. Drop in a file, pick an output format, and the conversion happens on your own device. Nothing is uploaded.
A project by an indie developer · transcodr.com
What it is
Most online converters upload your file to a server, convert it there, and hand back a download — which means your media leaves your device, sits on someone else’s machine, and is often capped, watermarked, or hidden behind a signup. Transcodr takes the opposite approach: the converter is the ffmpeg engine, and it runs in your tab.
That makes it private by construction, free to run, and usable on anything with a modern browser — no install, no account, no watermark.
How it works
Under the hood, Transcodr ships a build of ffmpeg compiled to WebAssembly. When you add a file, it is read into memory and processed by that engine right there in the browser. You get the same encoders the command-line tool uses — H.264, VP9, AAC, Opus, MP3, libwebp and more — with a live ffmpeg log so you can see exactly what is happening.
- The first conversion downloads the ffmpeg core (~32 MB) from a public CDN, then caches it.
- Subsequent conversions run offline, on your device, with no further network calls for your media.
- A batch queue lets you line up multiple files; each is encoded in turn and downloaded locally.
Privacy by design
Because there is no server doing the conversion, your files have nowhere to leak to. The input, the output, and everything in between stay on your machine, and closing the tab discards it all. The full details are on the privacy page.
What you can convert
Transcodr handles four kinds of media, in essentially any sensible combination:
- Video — MP4, WebM, MOV, MKV, AVI, animated GIF.
- Audio — MP3, WAV, FLAC, OGG, AAC, M4A, Opus.
- Images — PNG, JPG, WebP, AVIF, HEIC.
- Subtitles — SRT, VTT.
Some of the most popular conversions people reach for:
Frequently asked
Is Transcodr free?
Yes. Every conversion is free, with no account, no watermark, and no file-size paywall. The work runs on your own machine, so there are no per-conversion server costs to pass on.
Are my files uploaded anywhere?
No. Conversion happens entirely inside your browser tab using ffmpeg compiled to WebAssembly. Your files are read into memory locally and never sent to a server — there is no server doing the work.
How does it work without a server?
Transcodr ships a build of ffmpeg compiled to WebAssembly that runs directly in your browser. The first conversion downloads the ffmpeg core (about 32 MB) from a public CDN and caches it; after that, encoding happens offline on your device.
What can I convert?
Video (MP4, WebM, MOV, MKV, AVI, GIF), audio (MP3, WAV, FLAC, OGG, AAC, M4A, Opus), images (PNG, JPG, WebP, AVIF, HEIC) and subtitles (SRT, VTT) — in essentially any sensible combination.
Is there a file-size limit?
There is no hard limit, but because everything runs in your browser, very large files (multiple GB) can be slow or hit your browser’s memory ceiling. For most clips, photos and tracks it is fast.
Ready to convert something?
Open the converter