Change Video Speed Online - Speed Up or Slow Down, Free

Speed up or slow down a video

Drop a video here

or click to choose — MP4, MOV, M4V, WebM, MKV

Drop in a video, pick a speed from 0.1× to 16× and download it. Up to 120 frames a second the picture is not re-encoded: every compressed frame is copied as it is and only its timing changes, so the quality is exactly the original. The sound is sped up or slowed down without the chipmunk effect, or like a tape if you prefer, or removed. Nothing is uploaded and there is no watermark.

Nothing is uploaded — the file stays on your device
No file size limit
No sign-up, no watermark
Free, with no paid tier holding anything back

How to speed up or slow down a video

Drop an MP4, MOV, M4V, WebM or MKV into the box above. The line under it shows the length, picture size, frame rate and sound format.
Pick a speed: 0.25× to 16×, or type your own between 0.1 and 16. The preview plays at that speed straight away.
Choose what happens to the sound: Keep voices natural, Pitch follows speed or No sound. The plan line tells you the new length and frame rate before anything is written.
Press Change speed, play the result on the page, and download it.

Why the picture does not need to be re-encoded

A video file is a list of compressed frames, each with a time stamp saying when to show it. Playing a video twice as fast does not need different frames; it needs the same frames shown at half the time stamps. So this page copies every compressed frame as it is and only writes new times next to them. Nothing is decoded and encoded again, which is why it takes a fraction of a second and why the picture is exactly as sharp as before.

Most online speed changers do it the other way: they decode every frame and encode a new video, which costs time and some quality, and on the upload sites also a wait for the file to travel both ways. That is the right tool when you also add text or effects. For only changing the speed, copying is enough.

What we measured

We ran each case through this page in Chrome and read the result with a separate video library (PyAV), comparing the compressed frames with the original byte by byte. Our test clip has its frame number drawn into every frame and a steady 440 Hz tone (the A a tuning fork plays) as its sound.

File and speed	Video frames	Result	Sound
Test clip, 4 s, 30 fps, 2×	120 of 120 identical	2 s at 60 fps, frames 0–119 in order	still 440 Hz
Same clip, 2×, Pitch follows speed	120 of 120 identical	2 s at 60 fps	880 Hz (one octave up)
Same clip, 0.5×	120 of 120 identical	8 s at 15 fps	still 440 Hz
Same clip, 8×	15 kept, re-encoded	0.5 s at 30 fps: frames 0, 8, 16… 112	–
1080p phone video, 12 s, 12.16 MB, 2×	360 of 360 identical	6 s, 12.09 MB, done in 0.32 s	natural pitch, AAC
Portrait phone video, 1.5×	360 of 360 identical	still shown upright (1080×1920)	natural pitch, AAC
Chrome screen recording (WebM), 2×	240 of 240 identical	stays WebM, 4 s	natural pitch, Opus

The file hardly shrinks when you speed it up: the same frames are all still there, only shown faster. If you need a smaller file for a message or an upload form, run the result through Compress video afterwards.

The sound: why voices go squeaky, and how this page avoids it

Sound is different. Playing audio twice as fast doubles every frequency, which is the chipmunk voice: our 440 Hz tone came out at exactly 880 Hz with Pitch follows speed. The default, Keep voices natural, cuts the sound into short overlapping slices of 30 milliseconds and lays them closer together (or further apart) without playing any slice faster. Each slice is picked from the spot where it lines up best with the one before, so the waves join smoothly instead of clicking. On the test tone, 99.99% of the sound energy stayed at 440 Hz at both 2× and 0.5×.

Very large changes (4× and up, or below 0.5×) still sound processed, as they do in any editor; for a time-lapse you may prefer No sound.

Frame rate: smooth fast-forward, steppy slow motion

Because no frames are added or removed, the frame rate changes with the speed. A 30 fps phone clip becomes 60 fps at 2×, which plays smoothly anywhere. At 0.5× it becomes 15 fps and looks steppy, because slowing down cannot show moments the camera never recorded. For good slow motion, record at 60 or 120 fps (most phones have a slow-motion mode) and then slow it down here; 120 fps at 0.25× is still a smooth 30 fps.

Going the other way, a copied 30 fps clip at 8× would need 240 frames a second, which players stutter on and upload sites refuse. So above 120 fps the page switches to a time-lapse: it decodes the frames, keeps the one that falls on each 1/30-second step, and encodes a 30 fps H.264 video. The plan line says so before you start, and the result card counts the frames that were kept.

Good to know

Formats. MP4, MOV and M4V come out as MP4 (sound in AAC). WebM and MKV stay WebM (sound in Opus). The time-lapse path always writes MP4.
Phone videos stay upright. The rotation note a phone writes into a portrait video is carried over.
Long videos. The picture is copied almost instantly whatever the length. The sound is processed in your browser’s memory, roughly 60 MB per minute of stereo sound, so for anything longer than about half an hour choose No sound or cut out the part you need first with Trim video.
Sound only? For an audio file, Trim audio and Compress MP3 are the matching tools.

Frequently asked questions

How do I speed up a video?

Drop the video into the box, choose 1.25×, 1.5×, 2×, 4× or more (or type your own speed), and press Change speed. The preview above already plays at the speed you picked. Check the result on the page, then download it.

How do I slow down a video?

Choose 0.75×, 0.5× or 0.25×, or type a speed down to 0.1×. Keep in mind that slowing down cannot invent frames that were never filmed: a 30 fps clip at 0.5× plays at 15 frames a second and looks steppier. For smooth slow motion, film at 60 or 120 fps on your phone first; then 0.5× still gives 30 or 60 fps.

Does changing the speed lower the quality?

Not the picture, as long as the new frame rate stays at or under 120 fps. The compressed frames are copied byte for byte and only their timestamps change; the result card shows how many were copied. Above 120 fps (for example 8× on a 30 fps clip) the page re-encodes at 30 fps and keeps one frame in every few, like a time-lapse, and says so before you start. The sound is always re-encoded, because speeding sound up changes the sound itself.

Why do voices sound like chipmunks in other speed changers?

Playing sound faster also raises its pitch, the way a tape played fast does. The default setting here, Keep voices natural, stretches or squeezes the sound in small overlapping pieces so the length changes but the pitch does not. If you want the tape effect on purpose, choose Pitch follows speed.

What happens to the frame rate?

With copying, the number of frames stays the same and the frame rate is multiplied by the speed: a 30 fps clip at 2× becomes 60 fps, at 0.5× 15 fps. The plan line under the buttons tells you the new frame rate before you start. Some apps and upload sites cap video at 60 fps and convert anything faster.

Which files work?

MP4, MOV, M4V, WebM and MKV that your browser can play. MP4, MOV and M4V come out as MP4 with AAC sound; WebM and MKV stay WebM with Opus sound. The time-lapse path (above 120 fps) always writes MP4.

Is my video uploaded?

No. The video is read and written by your browser on your own device. There is no upload, no account, no daily limit and no watermark.

Can I also cut or rotate the video?

Not on this page. Use Trim video to cut the start or end first (a shorter clip is also faster to process), Rotate video to turn it, and Compress video if the result is too big to send.