Video Speed Changer to Speed Up or Slow Down Video Online

By the team at VidHaul

Some clips are too long to watch at normal speed: a cooking video, a drawing, a car ride or a screen recording of a long task. Other moments, like a jump, a dance step or a splash, look better slowed down. This video speed changer does both. You can speed up video online free or slow it down to slow motion, then download a new file that plays at that speed everywhere. Unlike the speed button in a video player, which only changes playback on your own screen, the change is saved into the video itself. It works as an online video speed changer in any current browser on a computer, iPhone or Android phone, and the video is never uploaded: the work happens on your device.

How does the video speed changer work?

Every frame in a video has a time stamp that says when it should appear. To change the speed, the tool divides each time stamp and each frame’s duration by the speed you pick, then encodes the frames again (H.264 for MP4, MOV and MKV, VP9 for WebM). At 2× a frame that used to appear at 10.0 s now appears at 5.0 s. No frames are thrown away and no new frames are invented, so the new length is simply the old length divided by the speed.

The sound is decoded and played back faster or slower inside the browser’s audio engine, like a tape played at a different speed, and saved as 48 kHz stereo at 128 kbps (AAC, or Opus for WebM). Because the sound is sped up as a whole, its pitch changes too. If you untick Keep sound (pitch follows speed), the result has no sound track.

Worked example (our own test, 24 October 2026, Chrome on a desktop): a 10-second clip at 2× came out at exactly 5 seconds, and the same clip at 0.5× came out at 20 seconds. That is the formula: new length = old length ÷ speed.

How to speed up a video

1. Click the box at the top of the page or drag your video onto it.
2. Open the Speed list. 2× is already selected; pick 1.25×, 1.5×, 3× or 4× if you want a different speed.
3. Leave Keep sound ticked to keep the audio, or untick it for a silent clip.
4. Press Start, wait for the progress bar, then click Download.

To slow a video down, do the same and pick 0.75×, 0.5× or 0.25× instead.

How long will my video be at each speed?

The chart shows what happens to a 60-second clip at each speed in the list. Slow speeds make the file much longer, which also means more work and a bigger file.

Which speed should you choose?

The frame rate and pitch columns are computed from how the tool works: frames keep their count but are squeezed or stretched in time, and the sound is resampled. A 30 fps clip slowed to 0.25× shows only 7.5 frames per second, so it looks choppy. Slow motion looks smoothest when the original was filmed at a high frame rate, such as a phone’s 60 fps or slo-mo mode.

How to speed up video on iPhone

You do not need an extra app. Open this page in Safari or Chrome on your iPhone, tap the file box and pick the video from your photo library or the Files app. Choose the speed and press Start. When it finishes, tap Download; the file goes to the Downloads folder in Files, and you can save it to Photos from the share menu. Keep the tab open and on screen while it works, because iOS can pause tabs in the background.

How to speed up video on iPhone more than 2x

Pick 3× or 4× in the Speed list. If you need even faster, for example 8× for a long time-lapse, run the result through the tool a second time: 4× and then 2× gives 8× in total, and 4× twice gives 16×. Each pass re-encodes the video, so use the fewest passes you can.

How to speed up video on Android

Open this page in Chrome on Android, tap the file box and choose the video from your gallery or files. Pick a speed and press Start. The new video is saved to your Downloads folder. Phones are slower than computers and everything is done in the phone’s memory, so very large files (over about 1.5 GB) may be slow or fail. A short clip for WhatsApp or Instagram is usually quick.

How to speed up video on Instagram and Instagram Story

If you want a sped-up clip for a Reel or a Story, make the fast version here first and post that file. Pick 1.5× or 2× for a lively Reel, or 3× to 4× to squeeze a long process into a short Story. Because the speed is part of the file, it plays the same on Instagram, WhatsApp Status and YouTube Shorts. If the clip needs a different shape for Stories, resize it to 9:16 afterwards with resize video.

Speed up video online free, without CapCut or Premiere Pro

Many people search how to speed up a video in CapCut or Premiere Pro. Those editors have speed controls inside a full editing project, and they can do far more than this page, such as speed ramps or keeping the voice at its normal pitch. If all you need is one clip at a new speed, a full editor is a lot to install and learn. This page does only the speed step and gives you a ready file that you can still import into any editor later.

Keep sound or remove it?

With Keep sound (pitch follows speed) ticked, the audio speeds up or slows down together with the picture, so lips and sounds stay in sync. Because it is sped up like a tape, the pitch changes: at 2× voices sound high, like a chipmunk, and at 0.5× they sound deep and slow. That suits funny clips. If you do not want that, untick the box and the result is silent. You can then put fresh music on it with add music to video, a common way to make sped-up reels and time-lapses.

Tips for the best result

• Cut out only the part you want to change with the video cutter first. A shorter clip processes faster.
• Slow speeds make long files: a 5-minute video at 0.25× becomes 20 minutes.
• Repeat a short slow-motion moment with loop video, or play it backwards with reverse video.
• If the new file is too big to send, shrink it with the video compressor.

How accurate is the video speed changer?

The length is exact: the tool divides every time stamp by the speed, so a 10 s clip gives 5.0 s at 2×, as in our test. Honest limits:

• No frame blending. Slow motion does not create new in-between frames, so 0.25× of a 30 fps clip plays at 7.5 fps and can look jerky.
• High frame rates when speeding up. All frames are kept, so 4× of a 30 fps clip is a 120 fps file. Most players handle this, but some apps may convert it to a lower frame rate on upload.
• Pitch is not corrected. Voices change pitch with the speed. There is no option to keep the normal voice.
• It re-encodes. The picture is encoded again at a balanced quality setting, so the file size changes and the quality is close to, but not exactly, the original.
• Range. Speeds are fixed steps from 0.25× to 4×. Other values such as 1.1× are not available.

Why this tool is different

Most online speed changers upload your video to a server, change it there and let you download it again, often with a sign-up, a size limit or a watermark on the free plan. VidHaul uses the WebCodecs API, the video engine built into modern browsers, so the frames are decoded and encoded on your own computer or phone. The sound is reshaped with the browser’s Web Audio engine. The video is never sent anywhere, and once you have pressed Start the work keeps going even without an internet connection.

The method is simple and checkable. The new length is always the old length divided by the speed, so you can predict the result before you press Start. Nothing is dropped and nothing is invented. The tool does only what this page describes: it does not stabilise, crop, add effects or change the colours of your clip.

What we measure

We test with real files in a real browser. For this tool we check that the output length matches the formula at both ends of the range: a 10-second clip came out at 5 s at 2× and at 20 s at 0.5×. The chart and the frame rate and pitch columns above are not measurements; they are computed from the settings the tool uses, so they hold for any clip.

What we do not measure: we do not score visual quality, and we do not publish processing times, because they depend on your device. The result card shows the file size before and after, and Copy summary copies those numbers for your notes.

Sources

• MDN Web Docs: WebCodecs API - the browser video engine used to decode and encode the frames.
• Mediabunny: Converting media files - documents the per-frame process step used to change each frame’s time stamp.
• MDN Web Docs: AudioBufferSourceNode.playbackRate - how the sound is played faster or slower by resampling.
• MDN Web Docs: OfflineAudioContext - how the reshaped sound is rendered without playing it.

Only edit videos you own or have the right to use.