Video Speed Changer
Speed up or slow down any video for free — no sign-up, no uploads, nothing to install. Choose from seven speed presets with automatic pitch-corrected audio. Everything runs right in your browser, so your video never leaves your device.
Drop a video file here
MP4, WebM, MOV, AVI — up to 500 MB
How It Works
Choose your video
Drop any MP4, WebM, MOV, or AVI file up to 500 MB. Loads instantly into browser memory — nothing leaves your computer.
Pick a speed
Choose from seven presets: 0.25× to 4×. Slow motion or fast forward — each preset includes automatic pitch-corrected audio.
Process in your browser
FFmpeg WebAssembly re-encodes the video using the setpts and atempo filters entirely on your device. No upload ever occurs.
Download your video
The speed-adjusted MP4 saves straight to your device — no server round-trip ever occurs.
Your video stays on your device
Unlike cloud-based video editors, this tool never transmits your video to a server. All processing happens inside your browser tab using FFmpeg WebAssembly — a full-featured video encoder compiled to run natively in modern browsers. You can verify this by watching your network tab in DevTools — you'll see zero outbound video requests.
Pitch-corrected audio at every speed
Changing a video's speed without correcting the audio pitch produces the classic "chipmunk" effect at high speeds or an unnaturally deep voice at slow speeds. This tool uses FFmpeg's atempo filter to adjust tempo independently of pitch, so voices and music stay natural at every preset. For the extreme 0.25× and 4× speeds, two atempo filters are chained together (each handles 0.5× to 2×) to achieve the full range.
Common use cases
- Slow motion replays — drop to 0.25× or 0.5× to examine fast movements frame by frame.
- Speed-run through lectures — set to 1.5× or 2× to watch long recordings faster.
- Social media clips — create satisfying slow-motion or hyperlapse effects for reels and shorts.
- Accessibility — slow down fast-talking content to 0.75× for easier comprehension.
Supported formats and output
The tool accepts MP4, WebM, MOV, and AVI files up to 500 MB. The output is always an MP4 file (H.264 video, AAC audio) — the most compatible format for sharing across phones, tablets, and desktop computers without any additional software.
Frequently Asked Questions
Is my video uploaded to a server?
No. All processing happens locally in your browser using FFmpeg WebAssembly. Your video files never leave your device — nothing is transmitted to a server.
Does the audio stay in sync and sound natural?
Yes. The tool uses FFmpeg's atempo audio filter, which adjusts playback tempo without changing the pitch. Voices and music stay natural at every speed. For 0.25× the filter is chained (atempo=0.5,atempo=0.5) and for 4× it is also chained (atempo=2.0,atempo=2.0) to stay within FFmpeg's per-filter range.
What video formats are supported?
The tool accepts MP4, WebM, MOV, and AVI files up to 500 MB. The output is always saved as MP4 for maximum compatibility.
What speed presets are available?
Seven presets are available: 0.25× (quarter speed), 0.5× (half speed), 0.75× (three-quarter speed), 1.25×, 1.5×, 2× (double speed), and 4× (quadruple speed).
Is this tool really free?
Yes, completely free. No account, no sign-up, no watermarks, and no hidden fees. Because all processing runs on your own device, there are no server costs to pass on.
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