Trim Video
Cut clips with stream-copy or re-encode - drag & drop studio powered by ffmpeg.wasm.
OpenSpeed up or slow down video with synced audio tempo adjustment. - runs entirely in your browser. Free, fast and private.
Preview the original pacing before you retime.
From 0.5× slow motion to 2× fast forward.
Audio uses atempo so pitch stays natural when kept.
Use for tutorials, montages and time-lapses.
Change Video Speed is a free video & audio utility on OneDevToolkit. Speed up or slow down video with synced audio tempo adjustment. It runs in your browser for this session - use the workspace on this page to try it.
Need a related step? Open the Video & Audio hub at /video-tools/ or the <a href="/blog/">blog</a> for longer workflows.
Processes data instantly with no server round-trips.
Your data never leaves your browser. Nothing is uploaded.
Works in any modern browser. Nothing to download or install.
No limits, no sign-up, no credit card required.
Works on desktop, tablet and mobile devices.
Beautiful in both themes. Your preference is saved.
Keyboard shortcut
Run Change Video Speed on local files when you cannot upload client or work documents.
Process deliverables on-device and keep an audit trail with privacy receipts where supported.
Handle common video & audio tasks without installing desktop software.
Answers for this tool. For site-wide help, open the FAQ hub.
Video tools use ffmpeg.wasm in your browser after the engine loads. Your clip is processed locally - it is not uploaded to OneDevToolkit for conversion.
The first run downloads the FFmpeg WebAssembly engine (~30 MB). Later runs reuse the browser cache and start faster.
Common inputs include MP4, WebM, MOV, and MKV. Exact support depends on what your browser can demux and what FFmpeg can decode in-wasm.
Stream copy needs compatible codecs/keyframes. Switch to re-encode for frame-accurate cuts or mixed sources - Change Video Speed often retries automatically.
Shorter clips are safer in-browser. Very long 4K files may exhaust memory. Trim first if jobs fail or the tab freezes.
Most modes let you keep or drop audio. Check the Options panel before processing.
Yes for short clips. Prefer Wi-Fi for the first FFmpeg download and avoid huge phone recordings when possible.
Lower resolution, stronger compression, or shorter duration reduces size. The success banner shows before/after size when available.
OneDevToolkit does not add watermarks to Change Video Speed outputs.