Slow Down or Speed Up a Video Free (and Keep It Smooth)

To slow down or speed up a video, re-encode it with a new playback speed. In the Video Speed Changer, drop your clip, pick a speed chip from 0.25x to 4x, choose MP4 as the output format and click Change speed. The new length equals the original duration divided by the speed, and the soundtrack is retimed to match.

Free toolVideo Speed ChangerSpeed up or slow down video clips from 0.25x to 4x with synchronized audio pitch. All encoding happens directly in your browser without uploading files.Open the tool

What changes when you change video speed

A video file stores each frame with a timestamp that tells the player when to show it. Changing speed rewrites those timestamps. At 2x every frame appears twice as early, so the clip finishes in half the time. At 0.5x each frame stays on screen twice as long, so the clip runs twice as long.

That simple idea has three consequences worth knowing before you start:

• Duration is predictable. New length equals original length divided by the speed factor.
• Smoothness depends on the source frame rate. Speeding up never looks choppy, because you have more frames than you need. Slowing down can, because no new frames are invented.
• The audio has to be retimed too. Otherwise sound and picture drift apart. The Video Speed Changer stretches or compresses the soundtrack in time while keeping its pitch, so voices do not turn into cartoon squeaks when you speed up.

Changing speed is a re-encode, like converting a format. If you are new to codecs and containers, the guide to converting video files for any device or platform explains why MP4 with H.264 is the safe default for the result.

How to speed up or slow down a video in your browser

The Video Speed Changer runs in your browser tab, so the clip stays on your device the whole time.

1. Drop your video into the tool. MP4, WebM, MOV, MKV, AVI, FLV and 3GP files up to 1 GB are accepted. A preview player appears.
2. Wait for the one-time engine download on first use. The video engine is about 30 MB and is cached afterward.
3. Pick a Speed chip. The options are 0.25x, 0.5x and 0.75x for slow motion, and 1.25x, 1.5x, 2x, 3x and 4x for faster playback. 1.5x is selected by default.
4. Choose the Output format. MP4 (H.264) plays almost everywhere; WebM (VP8), MOV, MKV and AVI are there if you need them.
5. Click Change speed. A progress bar tracks the encode. Longer and higher-resolution clips take longer, because every frame is encoded again.
6. Check the result and download. The result card shows the new file with a preview player and its size next to the source size. Play it through once, then click Download.

The file name gets the speed added to it, which helps when you export several versions to compare.

Free toolVideo Speed ChangerSpeed up or slow down video clips from 0.25x to 4x with synchronized audio pitch. All encoding happens directly in your browser without uploading files.Open the tool

Which speed should you pick?

The table below uses a 60-second clip recorded at 30 fps. Durations are exact; the “new frames per second” column shows how many distinct source frames reach the viewer each second, which is what your eye reads as smoothness.

Speed	New duration of a 60 s clip	New frames per second (30 fps source)	How it usually looks	Good for
0.25x	240 s	7.5	Visibly stepped, like a flip book	Dramatic moments shot at 120 fps or higher
0.5x	120 s	15	Noticeably choppy with fast motion	Product details, pouring, fabric movement shot at 60 fps
0.75x	80 s	22.5	Slightly softer motion	Calmer pacing for demos
1.25x	48 s	37.5	Natural	Tightening talking-head clips
1.5x	40 s	45	Natural, speech still clear	Tutorials, screen recordings
2x	30 s	60	Brisk, speech hard to follow	Unboxing, assembly, setup walk-throughs
3x to 4x	20 s to 15 s	90 to 120	Time-lapse feel, speech unusable	Packing, cleaning, long processes

Above 60 frames per second, many players and upload platforms simply drop the extra frames, which is fine: the motion still looks fast and fluid.

Getting smooth slow motion from the start

The most important slow-motion decision happens before you open any tool. Slowing down only looks smooth when the camera captured extra frames.

• Footage shot at 60 fps slows to 0.5x and still shows 30 new frames per second.
• Footage shot at 120 fps slows to 0.25x at 30 new frames per second.
• Footage shot at 240 fps gives smooth results at the slowest setting with room to spare.

Most phones label these modes “slo-mo” or offer 60 fps in the camera settings. Be aware that a slow-motion clip can play differently inside the phone’s gallery than it does once exported, so check how the exported file actually plays before slowing it further. iPhone slo-mo exports are often MOV files; if a platform rejects the result, the MOV to MP4 converter fixes the container.

Tidy up the result before you share it

Speeding up does not always shrink a file as much as you expect, because a 2x clip packs twice the motion into each second. Slowing down makes files longer and larger. If the result is too big for an upload form or chat app, run it through the video compressor with a target size in MB.

If your original is an MKV recording from screen capture software, the MKV to MP4 guide explains what to expect from the conversion, and the MP4 video converter handles it before or after the speed change.

Common mistakes

• Slowing down 30 fps footage to 0.25x. Motion turns into a slideshow. Record at 120 fps or higher for heavy slow motion, or stay at 0.75x with standard footage.
• Speeding up the whole clip when only one section drags. The good parts rush by too. Trim the slow section into its own clip, speed that up, and join the parts afterward.
• Expecting speech to survive 3x or 4x. Words blur together even with pitch preserved. Use 1.25x to 1.5x for talking clips and add captions if you go faster.
• Stacking speed changes on the same file. Each pass is another lossy encode, and fine detail softens. Work from the original clip and pick the final speed in one pass.
• Choosing AVI for a web upload. Older containers are often rejected by browsers and phones. Pick MP4 (H.264) unless the destination asks for something else.
• Processing a very long, high-resolution file on a low-memory laptop. The tab can run out of memory. Trim to the part you need or lower the resolution first.

Frequently asked questions

Does speeding up a video make the voices sound high-pitched? No, the Video Speed Changer retimes the audio without raising its pitch. The soundtrack is stretched or compressed in time, so speech at 1.25x or 1.5x stays natural. At extreme settings such as 3x, 4x or 0.25x speech becomes hard to follow even though the pitch stays the same.

Why does my slowed-down video look choppy? It looks choppy because slowing a clip spreads the same frames over more time. A 30 fps clip at 0.5x shows only 15 new frames per second. For smooth slow motion, record at 60, 120 or 240 fps and slow that footage down instead.

How long will my video be after changing the speed? The new duration is the original duration divided by the speed factor. A 60-second clip becomes 30 seconds at 2x and 120 seconds at 0.5x.

Can I change the speed of only part of a video? No, the Video Speed Changer applies one speed to the whole file. Trim the section you want into its own clip first, change its speed, and join the pieces afterward if you need a mixed-speed edit.

Wrapping up

Pick the speed by purpose: 1.25x to 1.5x to tighten talking clips, 2x to 4x for long processes, and slow motion only when the footage has the frames to support it. Everything else is one click. Open the Video Speed Changer, choose a chip, export as MP4 and check the playback before you publish.