Nothing leaves your device
Every byte stays in your browser tab. No upload, no server round-trip, no copies you can't see.
Why not upload
Free online MP4 converter without the upload.
Uploading is not part of converting a video. It is what happens when the converter runs on a computer that isn't yours — and it is almost all of the wait.
Every other converter
8 minutes Your video is sent to their computer and the result is sent back. That round trip happens before anything is converted.
WAVE
MP4
0 minutes The converter is already on your computer. Your video stays where it is and never goes anywhere.
A 1.2 GB video takes about eight minutes to upload on a typical home connection (around 20 Mbit/s up), and the result still has to come back down. Converting takes about the same time either way — it is the same work. The round trip is the only part Wave removes, and it is most of the wait. The animation is sped up.
Every other converter
Upload · queue · download
Wave
Drop · convert · save
The file
Uploaded to their server
Never leaves the tab
Progress bar
Actually your upload speed
The actual conversion
“Deleted later”
You take their word for it
No server = no copy to delete
File size
Free tier caps or queues you
8 GB per file, no queue
Terms of service
You grant a licence to your file
MIT site · LGPL FFmpeg
Under the hood · real time
What a conversion actually looks like.
wave://engine · sample.mkv → sample.mp4
ready
- INIT engine 30 MB WASM · once per session
- MOUNT sample.mkv 24.3 MB · in-memory only
- PROBE streams 1× H.264 · 1× AAC · 1080p
- PLAN route streams already fit MP4 → remux
- REMUX container Matroska → ISO base media · no re-encode
- WRITE sample.mp4 24.3 MB · fast-start atom · 2.1 s
0
bytes uploaded
2.1s
total
100%
local
How it works
Three steps.
No upload in any of them.
Wave is a converter with no upload stage. Here is the whole pipeline — three stages, all of them inside the tab you are reading this in.
Scope · your browser tab
Servers involved 0
-
01
Drop your file
Drag a video onto the card, or pick one from your device. The browser hands Wave a reference to the bytes already sitting on your disk — nothing is copied anywhere first.
-
02
The engine runs here
A WebAssembly build of FFmpeg loads once, then works on your own processor. When the streams already fit an MP4 container, Wave remuxes instead of re-encoding — same quality, seconds instead of minutes.
-
03
Save the result
MP4 for the video, MP3 if the audio was all you wanted. The file is written with a fast-start atom so it plays the moment it opens, and it lands straight in your Downloads folder.
Don't take our word for it: open DevTools, sit on the Network tab, and convert something. Wave pulls its engine down once, from this domain. After that the tab makes no request at all — there is nowhere for your file to be sent.
Why Wave
The converter that respects your files.
Fast when it can be
If the streams already fit MP4, Wave repackages instead of re-encoding. Same quality, seconds instead of minutes.
Free. No account. No file limits.
Convert as many files as you want. No sign-up wall, no "10 free conversions" gimmick, no watermark on the output.
Real MP4, real playback
Output ships with a fast-start atom so it plays everywhere - QuickTime, VLC, Windows, iOS, Android, the web.
Audio, too
Grab just the audio from any clip as an MP3 - same offline pipeline, one universally-playable format.
Open, LGPL-only
Built on FFmpeg's LGPL core. No GPL contamination, no closed encoders - the engine you can inspect.
FAQ
Answers, briefly.
Do you actually upload my video anywhere?
No. Wave loads a WebAssembly build of FFmpeg into your browser and runs the whole conversion locally. You can open your browser's network tab while you convert and see for yourself - no file bytes go out.
Is it really free?
Yes. No sign-up, no trial, no per-file limit, and no watermark on the output. The conversion itself always stays on your device and free to use.
How large a file can I convert?
Up to 8 GB per file. Wave streams the source through the WebAssembly engine in chunks (via WORKERFS) and, on Chrome and Edge, can save the output straight to disk with the File System Access API instead of buffering it in RAM - so the ceiling is really about your browser's decoder headroom, not file size. A warning appears above 2 GB so you know it'll take a while.
Which formats does it read?
MP4, MOV, MKV, AVI, WEBM, FLV, TS, 3GP, M4V, and most other common containers. When the input already contains H.264, HEVC, AAC, or MP3, Wave copies the streams straight into MP4 - no re-encode.
Why is my "just repackage" conversion so fast?
Because there's no encoding involved. Wave inspects the source, and if the video and audio streams already fit inside MP4, it just changes the container. The pixels and samples are untouched - same quality, a fraction of the time.
Can I extract audio from a video?
Yes, from any video Wave can read. On the conversion screen, pick MP3 as the output format - Wave discards the video and re-encodes the audio through LAME at 192 kbps. There is a dedicated video to MP3 page and per-format extract pages (MP4, MKV, MOV, and more). Output is MP3 on purpose - one format that plays on every device that plays sound.