Video Speed Changer
Speed up or slow down a video (with matching audio pitch correction) for time-lapses or slow-motion effects.
What is Video Speed?
A playback-speed editor for video: compress a long process into a fast time-lapse, or slow a moment down for emphasis.
How it works
Video timestamps are rescaled with the setpts filter while the audio is time-stretched with atempo so the pitch stays natural. A silent-video fallback handles clips that have no audio track at all.
- Load your file. Drag a file onto the drop zone or pick one from your device. It is read locally by the browser and never uploaded.
- Set the options. Adjust the handles, format, quality or threshold controls — the preview updates as you change them.
- Process and download. Run the tool, then download the result. Compare the reported before/after size for compressors and converters.
Examples
A 42 MB podcast episode → 9 MB MP3
Trim the intro, normalise to −16 LUFS, and export at 96 kbps mono — a typical interview lands around a fifth of the original size.
A phone video with the wrong orientation
Rotate 90° and the width/height swap in the output, so it plays upright in every player instead of relying on metadata flags.
Common mistakes
Expecting instant encoders
Video encoding runs in single-threaded WebAssembly, so a clip takes roughly its own length (or a little longer) to re-encode. Stream-copy operations are near-instant by comparison.
Re-encoding when a copy would do
Trimming, removing audio and joining same-codec clips can copy streams without re-encoding — pick the copy option when it is offered to avoid any quality loss.
Ignoring the first-load download
The media engine is about 31 MB and is fetched on first use, then cached. The first conversion on a connection is slower than every later one.
Frequently asked questions
Does the audio sound like a chipmunk?
Not unless you ask it to. Pitch correction is on by default; switch it off for the classic sped-up effect.
What speed should a time-lapse use?
4×–8× suits screen recordings and slow processes. Going beyond 8× starts dropping frames visibly.
Does slowing down improve quality?
No — slow motion interpolates timestamps, it cannot invent detail that was never recorded. High-frame-rate source footage looks best slowed down.