Bottom Line Up Front (BLUF): Boost video frame rates (FPS Booster ×2/×4) or create smooth slow motion (Smooth Slow Motion ×2/×4) entirely in your browser. Intermediate frames are generated using optical flow motion estimation rather than simple duplication. Everything runs on your device — no files are uploaded, no tokens are spent, and audio is preserved.
The tool analyzes consecutive video frames, calculates motion vectors between them, and synthesizes intermediate frames. This makes motion remarkably smooth when raising FPS or slowing down action without stutter.
Unlike traditional video slowdown that simply duplicates frames, optical flow motion interpolation computes the exact intermediate position of moving elements, preserving fluid and natural motion.
Your video never leaves your computer: decoding, interpolation, and encoding run directly inside your browser using WebGL and WebCodecs. This guarantees privacy and zero token consumption.
Hardware-accelerated WebGL shaders compute motion on the GPU, with a reliable CPU fallback if needed.
FPS Booster mode preserves original duration while multiplying frame rate by ×2 or ×4 (e.g. converting 30 FPS to 60 or 120 FPS). Audio remains at original playback speed.
Smooth Slow Motion mode stretches duration by 2× or 4×. Video plays smoothly at the target frame rate while audio is time-stretched in sync with the video.
Source frame rate and duration are detected automatically. You can choose Auto or specify an explicit target FPS: 30, 48, 60, or 120 FPS.
The finished video can be downloaded as MP4 (H.264 + AAC) or WebM (VP9/VP8 + Opus) depending on browser support.
Yes. In FPS Booster mode, original audio is preserved at 1× speed. In Slow Motion mode, audio is time-stretched in sync with the slowed video.
No. The entire process runs client-side in your browser.
No, it is completely free and runs without server inference.
Common video formats including MP4, WebM, and MOV are supported. For best performance and fastest processing on your device, videos up to 1080p and a few minutes in duration are recommended.