How to Use
- Click the drop zone above or drag-and-drop your video file (MP4, WebM, MOV, AVI, MKV).
- Select a preset speed (0.25× to 4×) or drag the custom slider to any value.
- Choose how to handle audio: keep it (auto-adjusted) or mute it.
- Click Process Video and wait for FFmpeg to re-encode the file in your browser.
- Click Download Video to save the speed-adjusted file to your device.
Features
100% Browser-Based
Powered by FFmpeg.wasm — your video never leaves your device.
Flexible Speed Range
From 0.1× ultra slow-motion to 4× time-lapse. Any increment.
Audio Control
Keep adjusted audio or mute it entirely — your choice.
MP4 Output
Always outputs MP4 (H.264/AAC) for maximum device compatibility.
Mobile Friendly
Works on modern Android and iOS browsers without any app install.
Completely Free
No sign-up, no watermark, no file size caps beyond device memory.
Use Cases
FAQ
What video formats are supported?
The tool supports MP4, WebM, MOV, AVI, and MKV input files. The output is always MP4 (H.264 + AAC) for maximum compatibility.
Is my video uploaded to a server?
Absolutely not. All video processing is done inside your browser using FFmpeg compiled to WebAssembly. Your file never leaves your device.
What speed values can I use?
You can select any speed from 0.1× (extreme slow motion) to 4× (fast forward). Use the preset buttons for common values or the slider for precision.
Does changing speed affect audio?
Yes. When you choose 'Keep (adjusted)', the audio pitch is preserved as closely as possible using FFmpeg's atempo filter. You can also choose to mute audio entirely.
Why does processing take a while?
FFmpeg re-encodes the entire video in your browser — a CPU-intensive task with no server assistance. Larger files or slower CPUs take more time. Closing other tabs can speed it up.