Video speed · Mac and iPhone
Speed up or slow down a video, with everything kept in sync
Every tutorial has a stretch where nothing happens: an install, a build, a form being filled in. Speeding that part up keeps the video moving without cutting out the proof that it works, and a slow-motion beat right before a reveal does the opposite job.
The hard part of retiming is everything else on the timeline. Zella shifts captions, zoom blocks and keyframes to their new times for you and leaves the music at its own speed, so a 2× stretch never turns your soundtrack into a chipmunk.
- Mac and iPhone
- Free, with Pro export extras
Quick answer
To speed up a video on iPhone or Mac in Zella, cut out the part you want and set its speed: 2× halves that part's length, and anything below 1× is slow motion. Audio is pitch-corrected, captions and zooms move to their new times, and background music keeps playing at its normal speed. Constant speed and Reverse are free on both, and on iPhone Instant Replay and Rewind are free too; smooth speed ramps belong to Zella Pro's depth toolset ($89 once, Mac and iPhone).
How to do it in Zella
-
Step 1: Cut out the part to retime
On the Mac, press B at the start and at the end of the stretch to split it out. On iPhone, cut the clip on the timeline at each end.
-
Step 2: Mac: set the speed in the transport
Select the segment and open the 1× ▾ control in the playback bar. Choose 2× or faster to speed it up, or a value below 1×, such as 0.5×, for slow motion.
-
Step 3: iPhone: open Speed
Select the clip and open Speed in the editor's tool row. Slow it down or speed it up, or pick Reverse, Instant Replay to repeat a beat, or Rewind to play forward and whip back.
-
Step 4: Add a speed ramp with Pro
A ramp eases from slow into fast and back instead of jumping to one number. It is part of the depth toolset; on the Mac, the Advanced switch in the top toolbar reveals it.
-
Step 5: Play it back and export
Check the retimed stretch. Captions, zooms and keyframes have already moved with it, and the export bakes the new timing in.
Why do it this way
Everything stays in sync
A caption at 6 seconds inside a 2× stretch moves to where it now belongs, and zoom blocks and keyframes follow the same way, with nothing to line up by hand.
No chipmunk voices
Sped-up speech is pitch-corrected, ramps included, and background music keeps its normal speed under the faster picture.
The same tools on both
The phone's retiming matches the Mac's, so a project you speed up on iPhone behaves the same when you hand it to the Mac as a .zella file.
What you need
- macOS 14 Sonoma or later (Apple Silicon or Intel), or iPhone on iOS 18 or later
- Free on every tier: constant speed, slow motion and Reverse, plus Instant Replay and Rewind on iPhone, no watermark, exports up to 2 minutes at 1080p
- Zella Pro ($89 once, Mac and iPhone) for speed ramps, part of the depth toolset; on the Mac the replay and rewind moves come with them
Questions
How do I speed up part of a video?
Cut the part out first. On the Mac, press B at each end, select the segment and choose 2× in the 1× ▾ control; on iPhone, select the clip and open Speed. The video's total length updates straight away.
Does speeding up a video make the voice sound like a chipmunk?
No. Zella corrects the pitch of sped-up audio, including during ramps, and background music keeps playing at its normal speed.
What is a speed ramp, and is it free?
A ramp speeds up and then slows down smoothly across a stretch, instead of one fixed speed. It belongs to Zella Pro's depth toolset on Mac and iPhone. A project that already uses a ramp still previews and exports on every tier, and every new install gets Pro Week: 7 days of Pro with no card.
Can I reverse a clip or add an instant replay?
On iPhone, Reverse, Instant Replay and Rewind are free alongside constant speed. On the Mac, Reverse is part of the free speed set, and the replay and rewind moves come with Pro's speed ramps.
Will my captions stay in sync after a speed change?
Yes. Captions, zoom blocks and keyframes shift to the new timing automatically, so they stay on the words and moments they belong to.
Related tools
Read the manual