Change Video Speed
Speed up or slow down a video (with pitch-corrected audio) locally in your browser.
Loading Change Video Speed… If nothing happens, please enable JavaScript.
Changing the speed of a video lets you stretch a moment out for a slow-motion look or compress a long take into a quick, watchable clip. Slowing footage down (to 0.75x or 0.5x) is great for reviewing technique, savouring detail, or adding a dramatic feel, while speeding it up (1.25x, 1.5x, 2x, or even 4x) turns lengthy walkthroughs, screen recordings, and time-lapse style shots into something far shorter without cutting anything out. This tool changes both the picture and the sound together, so the audio still matches the action at the new pace.
Frequently asked questions
Is my video uploaded to a server?
Does the audio stay at a normal pitch?
What happens to a video that has no sound?
Why is 4x done in stages?
Does changing speed affect the frame rate?
What format does it output?
Will speeding up a video make the file smaller?
Does it work offline?
About Change Video Speed
It all runs inside your browser using a WebAssembly build of FFmpeg. Your file is read locally, the video frames are retimed and the audio is resampled to follow, then the result is re-encoded as MP4 and returned as a download. Nothing is uploaded to any server, which makes the tool safe for private recordings, confidential screen captures, or any footage you would prefer to keep on your own device.
The audio gets special handling. Naively retiming sound would change its pitch (slowing it down turns voices into a low drone, speeding it up creates a chipmunk effect), so this tool uses tempo adjustment that keeps the pitch natural while changing the speed. For large jumps such as 4x, the tempo change is applied in stages to stay within the safe range of the audio filter, which preserves clarity. If a clip has no audio track at all, the tool detects that and simply retimes the video on its own.
Why fast audio used to sound like chipmunks
For most of recording history, changing a sound's speed and changing its pitch were the same operation, because both came from one physical control: how fast the medium moved. Spin a record faster or run a tape at a higher speed and everything rises in pitch as well as tempo, which is exactly how the famous high-voiced novelty recordings of the 1950s were made. Slow it down and voices drop into a slow, syrupy growl. Speed and pitch were chained together by physics, and there was no easy way to separate them.
Digital audio broke that link with a technique often called time stretching. Instead of simply playing samples faster, the software analyses the sound in short overlapping windows and intelligently repeats or skips tiny segments, so the tempo changes while the frequencies (and therefore the perceived pitch) stay put. Done well, a voice can be sped up to fit a shorter clip and still sound like the same person talking quickly, rather than a cartoon character. This is the same family of algorithms that lets podcast apps offer 1.5x playback without turning the host into a chipmunk.
The filter behind this tool works within a safe range for each pass to keep that illusion convincing, which is why large speed changes are applied in steps. Push any single time-stretch too far and the artefacts become audible: echoes, warbling, or a metallic edge. By chaining moderate adjustments instead of one extreme one, the audio stays clear even at 4x, and the picture and sound arrive at the new speed perfectly together.