Video Speed Changer: Speed Up or Slow Down Video Online, Free
Drop an MP4, MOV, WebM or MKV, choose a playback speed from 0.25× slow motion to a 4× fast-forward, and re-time video and audio together. Powered by FFmpeg compiled to WebAssembly, it runs 100% in your browser. Your footage is never uploaded, and the download carries no watermark.
What is the video speed changer?
The Video Speed Changer sets any playback speed from a 0.25× slow-motion crawl to a 4× fast-forward, with presets and a live readout of the new duration. Keep the audio pitch natural or drop the sound. Handles MP4, MOV, WebM, MKV and AVI. Free, in the browser, no uploads or watermark.
The GigAI Video Speed Changer re-times a clip the way a proper editor does (by re-encoding the frames, not by asking a player to fake it) so the exported file actually plays back faster or slower everywhere you take it. Drop a video and it probes the file locally, then hands you a speed control that runs from a dreamy 0.25× slow motion through real-time up to a brisk 4× fast-forward, with one-tap presets for the common jobs (½× slow-mo, 1.5× lecture skim, 2× time-lapse feel). You decide what the audio does: keep it and let FFmpeg's tempo filter stretch the sound while holding the original pitch so voices still sound like themselves, let the pitch ride up or down with the speed for the classic chipmunk or slowed-and-reverbed effect, or drop the audio track entirely for a clean silent time-lapse. When you run it, a self-hosted FFmpeg WebAssembly core does the re-timing on your device and hands the result straight back as a download, showing the new duration and file size next to the original. Because everything happens on your own machine, personal recordings, client footage and anything under NDA never leave the tab: there's no upload bar, no queue, and no watermark stamped across your result. It's honest about the trade-offs: WASM FFmpeg is single-threaded and memory-bound, so it's slower than a desktop app and happiest with files up to roughly a few hundred megabytes, and a live progress bar shows exactly where the re-encode stands the whole way through. Close the tab and every trace is gone.
- Difficulty:
- Medium
- Typical time:
- ~1–2m
- Processing:
- 100% browser processing
Last updated
How to use the video speed changer
- 1
Drop your video
Drag an MP4, MOV, WebM or MKV onto the workspace, or click to browse. It's read and probed locally: nothing is uploaded.
- 2
Pick a speed
Slide from 0.25× to 4× or tap a preset. The tool shows the exact multiplier and the resulting runtime so you know what you'll get before you commit.
- 3
Choose what the audio does
Keep the sound with its natural pitch, let the pitch change with the speed, or drop the audio for a silent time-lapse.
- 4
Change speed & preview
Hit Change speed and watch the progress bar. When it finishes, the re-timed clip plays back so you can confirm it before you save.
- 5
Download
Download the re-timed video, clean and watermark-free, and check the new duration and size against the original right on the result card.
What Video Speed Changer includes
0.25× to 4×: smooth or preset
Drag the speed slider anywhere from a 0.25× slow-motion crawl to a 4× fast-forward, or tap a preset (½×, 1.5×, 2×, 3×) for the common jobs. A live readout shows the exact multiplier and the new duration before you run it.
Three ways to handle audio
Keep the sound and hold its natural pitch so voices still sound right, let the pitch ride with the speed for the classic sped-up or slowed-down effect, or drop the audio entirely for a clean silent time-lapse.
See the new runtime up front
The tool does the math as you choose: a 4-minute clip at 2× reads 2 minutes, at 0.5× reads 8 minutes. No surprises when the encode finishes. The target duration is on screen the whole time.
Honest live progress
A determinate progress bar tracks the re-encode from start to finish, and a one-time note covers the first-run engine download. No spinner that leaves you wondering whether it hung.
Preview, size delta & one-click download
Play the re-timed result before you save it and see the new duration and file size next to the original, then download the clip. No sign-up, no email, no watermark.
100% in your browser
A self-hosted FFmpeg WebAssembly core does the re-timing on your device. Your video is never uploaded, queued or stored, which makes it safe for personal, client and NDA footage alike.
Why use our video speed changer
Keep private footage private
The usual way to speed up a clip online is to hand it to a random server. Here the re-encode runs on your machine, so recordings of your family, your clients or anything confidential never leave the tab.
No watermark, no account, no cap
Free speed tools love to stamp a logo across your export or gate the download behind a sign-up. This one just gives you the re-timed clip, clean, unbranded, and as often as you like.
Sound that still sounds right
Naïve speed-ups turn every voice into a chipmunk. Pitch-preserving audio keeps speech natural at 1.5× or 2×, so a sped-up tutorial or podcast is still easy to follow, and it's a toggle away when you want the effect instead.
Nothing to install
No desktop editor, no plugin, no FFmpeg command line to memorise. Open the page in any modern browser and you're re-timing in seconds. It even works offline once the engine has loaded.
Built for the way you work
From quick one-off fixes to daily workflows, see how people put this tool to use.
- Content creator
Fake a time-lapse
Speed a long build, unboxing or cooking clip to 3× or 4× so a ten-minute process becomes a punchy short, then drop the audio for a clean, music-ready silent time-lapse.
- Student / Professional
Skim a lecture faster
Bump a recorded lecture or meeting to 1.5× or 2× with the pitch held natural, so the speaker stays perfectly understandable while you get through it in half the time.
- Coach / Analyst
Study the detail in slow motion
Slow a sports rep, a golf swing or a UI interaction to 0.5× or 0.25× to see the frames that fly by at full speed, without a heavyweight editor or an upload.
- Anyone
Set the mood on a clip
Slow a moment down for a dreamy feel or speed it up for energy, and let the pitch ride with it for the sped-up or slowed-and-reverbed sound people expect, all in the browser.
Supported formats
Accepts MP4, MOV, WebM, MKV and AVI, and produces MP4, WebM and MKV, all processed locally in your browser.
- MP4
- MOV
- WebM
- MKV
- AVI
- MP4
- WebM
- MKV
Frequently asked questions
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Common problems, solved
Hit a snag? Here are quick fixes for the issues people run into most.
The first run takes a while before the progress bar moves.
The very first run downloads the FFmpeg WebAssembly engine (a one-time fetch that's then cached). You'll see a 'loading engine' note during that step. Subsequent runs skip it and start re-encoding immediately.
It slowed to a crawl or ran out of memory on a big file.
In-browser FFmpeg is single-threaded and works in your tab's memory, so very large or long high-bitrate clips are demanding, and slowing a clip down makes a longer, heavier output. Keep inputs loosely under a few hundred megabytes, or trim the clip first, then change its speed.
My sped-up video has no sound.
If the source had no audio track there's nothing to re-time, so the output is silent too. If you meant to keep sound from a clip that has it, make sure the audio mode isn't set to 'Remove audio' before you run.
The audio sounds a little different at extreme speeds.
Pitch-preserving audio stretches the sound with a tempo filter. At very high or very low multipliers that stretch can add faint artefacts. If it bothers you, switch to 'Let pitch change with speed' for a cleaner, if higher- or lower-pitched, result.
Get the most out of it
For skimming talks, 1.5× with natural pitch is the sweet spot, fast enough to save real time, slow enough to follow every word.
Making a time-lapse? Speed the clip up and set audio to 'Remove audio', then add your own music track afterwards for a clean result.
Slowing a clip down multiplies its length and file size. A 0.25× pass makes a clip four times longer, so keep the source short for the snappiest export.
Want the classic effect? 'Let pitch change with speed' gives you chipmunk voices sped up and the slowed-and-reverbed sound slowed down.
Keep inputs under a few hundred megabytes for the fastest run. The first run also downloads the engine once, so give the first change a moment.
What's new
Recent updates and improvements to the video speed changer.
Initial release, drag-and-drop input, 0.25×–4× speed slider with presets, pitch-preserving or pitch-changing audio, remove-audio option, in-browser FFmpeg WebAssembly re-encoding, live progress, preview, before/after duration and size, and a watermark-free download.
Added a live target-duration readout that updates as you change the speed, and clearer guidance that slowing a clip down produces a longer, heavier file.
Made silent sources graceful, clips without an audio track now re-time cleanly instead of erroring when audio was requested, and improved MOV/MKV probing.
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Your privacy is built in
Your video is read, probed, previewed and re-timed entirely in your browser using a self-hosted FFmpeg WebAssembly core. It is never uploaded to any server, queued, logged or stored. That makes the speed changer safe for personal recordings, client footage and anything under NDA. There's no account and no watermark, and once the engine has loaded the tool keeps working offline. Close the tab and every trace is gone.
- Runs in your browser
- No uploads
- Nothing stored
Ready to try the video speed changer?
Free, private and instant. Video Speed Changer runs right in your browser.