Speeding up or slowing down a video by physically re encoding it, rather than only setting a playback rate flag, is what makes the result behave consistently everywhere the file is opened. A flag based speed change only works in a player that respects it, while a video whose frames were actually recorded at the new rate plays correctly at that speed in absolutely any video player, on any device.
Everything runs locally. The browser decodes the source video, plays it back at the chosen rate, draws each resulting frame onto a canvas, and MediaRecorder captures that canvas to produce the output, so a private clip never has to be uploaded anywhere just to change its speed.
What a video speed changer is useful for
Fast forwarding long recordings such as lectures, screen captures or security footage reviews saves real viewing time, since a two hour recording sped up to double speed becomes an hour long file that still contains every frame in order. Slowing footage down is useful for the opposite reason, revealing detail in fast motion that is hard to follow at normal speed, such as a sports technique or a mechanical process.
Video editors also use speed changes creatively, for slow motion emphasis on a key moment or a fast forward montage effect that compresses a long process into a few seconds. Producing an actual sped up or slowed down file rather than relying on a player's own speed control means the effect survives being embedded, shared or played back on a device that has no speed control at all.
- Use a video speed changer to shorten a long lecture, meeting or screen recording into less viewing time.
- Slow footage down to reveal detail in fast motion that is hard to follow at normal speed.
- Produce an actual sped up or slowed down file for editing into a larger project, rather than relying on a player's speed control.
- Keep changes moderate, roughly between 0.5x and 2x, for the most watchable result.
Being honest about audio at non default speeds
Changing a video element's playback rate changes both its picture and its audio together, and different browsers handle the resulting audio differently. Some browsers apply pitch preservation automatically so a sped up voice does not turn into a chipmunk, while others simply resample the audio the way changing the speed of a tape would, letting pitch rise or fall with the rate. Because this varies by browser and this tool captures the audio track directly from the video element during playback, the pitch and clarity of the audio at anything other than 1x speed depends on what your specific browser does internally, and that behaviour is outside this tool's control.
If the audio in your result sounds off at a changed speed, or you only care about the picture, consider recording without the audio track and adding a separately processed soundtrack afterward, or use a dedicated audio speed changer on the audio only if precise pitch handling matters more than convenience.
Choosing a speed multiplier
Speeds between 0.5x and 2x stay easy to watch and follow, since both slower and faster motion still tracks naturally to a human eye at that range. This is the range best suited to fast forwarding a lecture or gently slowing down a demonstration without the result feeling jarring or unnaturally rushed.
More extreme speeds, down toward 0.25x or up toward 4x, are supported and useful for specific purposes such as detailed slow motion analysis or a rapid overview scrub through very long footage, but expect motion to look noticeably less smooth the further the setting moves from normal speed, since frame timing becomes more compressed or stretched at the extremes.
Re-encoding every frame at a new timestamp, not just relabelling
The source video's playbackRate property is set to your chosen multiplier before playback begins, which changes how quickly the browser advances through the file's frames. A canvas the same size as the source frame is drawn on every animation frame while the video plays at that adjusted rate, and MediaRecorder captures the canvas as a live stream, encoding the result as it goes.
Because the recording watches real playback happen rather than processing frames instantly, a sped up video finishes recording faster than its own original duration, while a slowed down video takes longer to record than it will eventually play back. No server is involved in any part of this pipeline.
How to change video playback speed
- 1
Add your video file
Drag a video file onto the drop area, or click it to browse. MP4, WebM and MOV are all accepted.
- 2
Choose a speed multiplier
Move the slider between 0.25x and 4x. Values close to 1x preserve the most natural motion.
- 3
Process the video
Press process. The video plays at the new speed while a canvas records the result in real time.
- 4
Download the sped up or slowed down file
Download the WebM result once recording finishes. Its duration reflects the chosen speed change.
Related tools worth bookmarking
Sources and further reading
- MDN: HTMLMediaElement.playbackRateThe property this tool uses to play the source video back at the chosen speed.developer.mozilla.org
- W3C: MediaStream Recording specificationThe specification defining how MediaRecorder captures a stream into an encoded file.w3.org
- WebM ProjectThe open format and codec suite that MediaRecorder writes the sped up or slowed video into.webmproject.org
Frequently asked questions
Common questions about the video speed changer.
Picture and audio are captured from the same playback session, so they generally stay aligned, but exactly how each browser resamples the audio track at a changed playback rate varies and is not something this tool controls. If audio quality at a changed speed matters more than convenience, process the audio separately with a dedicated audio speed changer.
It depends on the browser. Some browsers preserve pitch automatically when playback rate changes, keeping voices sounding natural, while others let pitch rise and fall with speed the way a tape does. This is a browser behaviour outside this tool's control, so results can differ depending on where you run it.
Recording watches the video actually play at the new speed, so a video sped up to 2x finishes recording in about half its original duration, while a video slowed to 0.5x takes about twice as long to record as it will eventually play back.
Roughly 0.5x to 2x tends to look the most natural, since motion still tracks smoothly to the eye at that range in either direction. More extreme speeds toward 0.25x or 4x are supported but can look noticeably choppier, since frame timing becomes more compressed or stretched.
Yes, in reverse. Since recording watches real playback at the chosen rate, dividing the source duration by the speed multiplier gives a close estimate: a ten minute video at 2x takes about five minutes to process, while the same video at 0.5x takes about twenty minutes, before either file is ready to download.
Yes. This tool lets you speed up video online directly in a browser tab, using the same playback and recording features already built into the browser, so there is nothing to install and no account required to produce a faster running file.
Set the speed slider well below 1x, such as 0.25x or 0.5x, and turn off the audio track if pitch and clarity are not needed for your analysis. This is a reliable way to slow down video file playback for studying motion in detail, at the cost of a longer recording time while the tool plays it back.
Yes. Speeds up to 4x are supported for a fast forward video export of long recordings such as lectures or security footage, though motion becomes noticeably choppier the further the setting moves from normal speed.