Does the audio stay in sync when I change the speed?

Yes. Crisp speeds up or slows down the audio to match the video and pitch-corrects it, so a sped-up clip doesn't sound chipmunky and a slowed one doesn't sound droning. Video and sound stay locked together.

How fast or slow can I go?

Anything from 0.1× (ten times slower) to 8× (eight times faster). Common choices are 2× and 4× to speed up, and 0.5× or 0.25× for slow motion.

Is this the same as slow motion?

Slow motion is just a speed below 1× — e.g. 0.5× is half speed. The Speed lane does both directions, so it covers slow-mo as well as speeding up. For extra-smooth slow motion, Crisp can also interpolate in-between frames.

Can I speed up and enhance in one step?

Yes. Ask for both in one breath — "speed it up and upscale to 4K" — and Crisp keeps the enhancement instead of dropping it.

Is my video uploaded anywhere?

No. Crisp changes the speed entirely on your Mac — nothing is uploaded, so there's no queue, no size cap, and your footage never leaves the device.

Guide · Change video speed on Mac

How to change video speed on a Mac

Whether you want to speed up a long clip into a snappy time-lapse or slow it down for a dramatic slow-mo, changing a video's speed shouldn't need a timeline editor, an account, or an upload to some website. Here's how to change the speed of a video on a Mac in seconds, 100% offline — anywhere from 0.1× to 8× — with the audio kept in sync and pitch-corrected and no watermark, either by typing it in plain English or by using the Speed lane.

Updated July 2026 · step-by-step

The fastest way: just ask

Crisp has a plain-English box ("Or just tell Crisp what to do…"). Drop your video in and say what you want:

speed it up (defaults to 2×) or speed it up 4x
slow it down (defaults to half speed) or 3x slower
make it 2x faster, double the speed
slow motion, half speed

Crisp reads the request, shows you the plan, switches to the Speed lane and sets the factor for you — you just press the button. And if you ask for a bigger edit in the same breath — "speed it up and upscale to 4K" — the enhancement rides along instead of being dropped.

The manual way: the Speed lane

Open Crisp and drop in your video

Get the free Crisp app for Mac and drag your clip onto the window. Nothing is uploaded — the whole job runs on your Mac.
Pick the Speed lane

Choose Speed in the task row. It's for video clips; if you've staged a photo, Crisp will nudge you to pick a video.
Choose a speed

Pick a preset — 2× faster, 0.5× (half speed) — or set any factor from 0.1× to 8×. Above 1 speeds up; below 1 slows down.
Press Change speed

Crisp rescales the video and pitch-corrects the audio on-device with hardware encoding, and saves the result beside your original — watermark-free. Staged several clips? It re-times each one in the same batch.

The audio is done right

Naively speeding up a clip makes voices sound like chipmunks; slowing it down makes them drone. Crisp pitch-corrects the audio as it re-times it, so a 2× clip still sounds natural and a 0.5× one stays intelligible — and the sound stays perfectly in step with the picture. It handles big changes too, chaining the time-stretch in stages so even 8× or 0.1× comes out clean.

Speeding up vs slowing down — and smooth slow-mo

Speed is one lane that goes both ways. A factor above 1× speeds the clip up (great for condensing a long screen-recording or making a time-lapse); a factor below 1× slows it down (0.5× is half speed, 0.25× is quarter-speed slow motion). For really smooth slow motion, Crisp can also interpolate extra in-between frames so the slowed clip doesn't look choppy — see the dedicated slow-mo guide.

Crisp vs iMovie vs QuickTime for changing speed

	Crisp	QuickTime	iMovie	Online tools
Speed up AND slow down	Yes — 0.1×–8×	No	Yes (presets)	Yes
Pitch-corrected audio	Yes	—	Often chipmunk	Varies
Plain-English ("slow it down")	Yes	No	No	No
Speed + enhance in one step	Yes	No	No	No
100% offline, nothing uploaded	Yes	Yes	Yes	Uploads your clip
No watermark	Yes	Yes	Yes	Often watermarked
Price	Free during beta	Free	Free	Free + upsell

QuickTime has no speed control at all; iMovie can change speed but often leaves the audio pitch-shifted. Crisp keeps it natural and does both directions in one lane.

Why offline matters for changing speed

Your footage stays yours. The web "change video speed online" tools upload your clip first. Crisp re-times it entirely on your Mac — nothing leaves the device.
No queue, no size cap. Cloud tools throttle by file size and make you wait; Crisp works on the whole file locally.
The audio sounds right. Pitch-corrected sound, locked to the picture, at any factor.
Batch a whole set. Stage several clips and Crisp re-times each one in a single batch.

Change your first clip's speed — offline

Free to try on your Mac. Speed up or slow down, pitch-corrected audio — no account, no watermark, nothing leaves your device.

Download Crisp for Mac

Apple Silicon · macOS 12+ · Notarized

FAQ

How do I speed up or slow down a video on a Mac for free?

Use Crisp: drop your clip in, pick the Speed lane (or type "speed it up" or "slow it down"), choose a factor, and press Change speed. It re-times the video and keeps the audio pitch-corrected, entirely on your Mac, with no account, no upload and no watermark.

Does changing speed keep the audio in sync?

Yes — Crisp re-times the audio to match and pitch-corrects it, so it stays in sync and sounds natural instead of chipmunky or droning.

How fast or slow can I make it?

From 0.1× (ten times slower) up to 8× (eight times faster). 2× and 4× are common for speeding up; 0.5× and 0.25× for slow motion.

Is slow motion the same thing?

Slow motion is just a speed below 1×. The Speed lane does both directions; for extra-smooth slow-mo, Crisp can also interpolate in-between frames.

Can I change a photo's speed?

No — speed only applies to video, so the Speed lane is video-only. If you've staged a photo, Crisp will point you to a video clip.