Video Speed Changer
Runs in your browser — your files are never uploaded.
Speed a video up or slow it down, from quarter speed to 4×, with the audio following correctly. That last part is where this differs from a naive command: ffmpeg’s tempo filter only accepts a factor between 0.5 and 2 in one pass, so anything beyond that has to be chained. Asked for 4× directly, some builds reject it and others silently discard the audio — leaving a video at the right speed with no sound and nothing to explain why.
How to use Video Speed Changer
- 1
Drop your video onto the box, or click to choose one.
- 2
Pick a speed — 2× halves the running time, 0.5× doubles it.
- 3
Click “Convert” to save the result.
Share
Embed this tool on your site
Paste this where you want the tool to appear. It runs entirely in your visitor's browser — no uploads, no account, no tracking.
Please keep the attribution line — it's what keeps these tools free.
Need a different size, a dark theme, or a different tool? Build an embed lets you preview it first.
Frequently asked questions
Does the audio go squeaky when I speed it up?+
No. The audio is time-stretched rather than resampled, so the pitch stays where it was and voices still sound like themselves. Resampling — the naive approach — is what produces the chipmunk effect.
Why do other tools lose the audio at 4×?+
Because the tempo filter accepts 0.5–2.0 in a single instance and 4 is outside it. Handled properly the filter is chained — two passes of 2× multiply out to 4× — but an unchained request is either rejected or, worse, dropped silently along with the whole audio track.
Will it stay in sync?+
Yes. The video timestamps and the audio tempo are derived from the same factor, so they cannot drift apart. Mismatching the two is the usual cause of audio that starts aligned and is seconds out by the end.
Does slowing a video make it smooth?+
Not by itself. Slowing down holds each existing frame on screen for longer, so heavy slow-motion looks juddery unless the footage was filmed at a high frame rate to begin with. There is no way to recover motion that was never recorded.