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Make a slow motion video

Slow a clip down to half, a quarter or a tenth of its speed, holding each frame or computing new ones for smooth motion, with nothing uploaded from your device.

Drop a clip to slow downMP4, MOV, WebM, MKV, AVI · up to 500 MB and 10 min free
Choose video
Runs in your browser · no uploadHow it works

How to use Slow motion video

  1. 1

    Add a short clip

    Drop an MP4, MOV, WebM, MKV or AVI video of up to 10 minutes. Slow motion works best on a few seconds of fast action.

  2. 2

    Pick how slow

    Choose 0.5×, 0.25× or 0.1×, or any speed down to a tenth with the slider; the preview plays at that speed right away.

  3. 3

    Choose the motion

    Hold frames is instant and lossless. Smooth computes in-between frames for flowing movement and shows how long that will take before you start.

  4. 4

    Set the sound and save

    Keep the pitch, let it drop like a film slow-mo, or mute it, then press Make slow motion and download the clip.

Limits and Pro

One clip at a time, up to 500 MB and 10 minutes, slowed to as little as 0.1×; smooth motion is offered while it would take under about 10 minutes.

Pro opens videos of up to 4 GB and 10 hours; smooth motion keeps its length cap, which depends on what a browser can compute. See Pro

About Slow motion video

Slow motion video stretches a clip to two, four or ten times its length, and there are two ways to fill the extra time. Hold frames, the default, keeps every original frame and shows each one for longer. Nothing is re-encoded, so it finishes in seconds with no loss, but a clip only has the frames it was filmed with: a 30 fps video at 0.25× shows 7.5 new pictures a second, and fast movement looks steppy. That is exactly what repeating each frame four times would look like. Footage shot at 60, 120 or 240 fps has frames to spare, so it slows down smoothly this way.

Smooth asks ffmpeg's minterpolate filter to estimate the motion between frames and draw new pictures in the gaps, giving fluid slow motion at the clip's own frame rate. It is heavy work for a browser: the clip is processed at up to 720p and re-encoded as H.264, and a few seconds of video can take a minute or more, so the option appears only when the estimate stays under ten minutes. Interpolation can smear or warp fast edges, hands, and anything passing in front of something else.

The sound can be stretched at its own pitch, dropped in pitch for the classic deep slow-motion roar, or removed. Good subjects are a trick, a jump, a splash, a pet catching a treat, or a golf or tennis swing you want to study frame by frame.

Privacy

Every frame stays on your computer or phone: the clip is slowed down, and for smooth motion interpolated, by ffmpeg.wasm in a Web Worker in this tab, with no upload. The 31 MB engine is fetched from jsDelivr on first use only and then cached by the browser.

Features

Down to 0.1×

Presets at half, a quarter and a tenth of normal speed, and anything between.

Smooth motion

Computed in-between frames for short clips, with a time estimate up front.

Instant hold-frame mode

Frames are retimed rather than re-encoded, so the picture keeps its quality.

Deep slow-mo sound

Let the pitch drop with the speed, keep it level, or mute the clip.

Slow motion video: frequently asked questions

Does slow motion repeat frames?
Ordinary slow motion does, in effect. With Hold frames, each original frame stays on screen longer instead of being duplicated, which looks identical to repeating it: at 0.5× every frame shows twice as long. That keeps the original quality and takes seconds, but motion turns jerky at low speeds unless the clip was filmed at a high frame rate. Smooth creates genuinely new frames instead.
What does the Smooth option do?
It runs motion-compensated frame interpolation with ffmpeg's minterpolate: the tool estimates where each block of the picture moves between two frames and draws the pictures in between, so a 30 fps clip at 0.25× still shows 30 different frames a second. This needs a lot of computing, so it works at up to 720p, takes minutes, and is offered only for short clips.
How slow can I make a video?
Down to 0.1×, which turns a 3-second clip into 30 seconds. The presets are 0.5×, 0.25× and 0.1×, and the slider or the exact field accept anything in between. At a tenth of the speed a 30 fps clip holds each frame for a third of a second, so Smooth or high-frame-rate footage gives a far better result there.
Will 60 fps or 120 fps footage look better?
Yes, much better. Slow motion needs frames, and high-frame-rate footage has them. A 120 fps clip slowed to 0.25× still shows 30 real frames every second, as smooth as normal video, with no interpolation and no re-encoding. If your phone or camera has a 60, 120 or 240 fps mode, film the action with it and slow it down here.
What happens to the sound in slow motion?
You choose. Keep pitch stretches it with ffmpeg's atempo filter so voices stay at their own pitch, although at 0.25× and below they sound washed out. Change pitch slows the samples down, so everything drops an octave at 0.5× for the familiar deep slow-motion effect. Mute removes the audio track, and many slow-motion clips are better off without one.

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