How to Edit Video Speed on iPhone | Slo-mo, Fast, & iMovie

You can edit video speed on iPhone for Slo-mo clips in the Photos app, and for any video using the free iMovie app.

A video that drags or plays back at a breakneck pace rarely captures the moment the way you remember it. Speeding up a long clip or slowing down a fast one takes just a few taps on iPhone, but the method depends on the video itself — and the free tools already on your phone cover both cases. The built-in Photos app only adjusts speed for footage shot in Slo-mo mode; for every other video, Apple’s iMovie handles the job without costing a thing.

The Built-in Method: Editing Slo-mo Clips in Photos

If you shot the video in Slo-mo mode on your iPhone, changing its playback speed or defining the slow-motion segment takes seconds inside the Photos app.

1. Open the Photos app and tap the Slo-mo video you want to edit.
2. Tap Edit in the top-right corner.
3. Tap the Video button at the bottom of the screen.
4. Tap Playback Speed and choose a speed setting to apply to the entire clip.
5. To control where the slow-motion effect plays, drag the two black vertical bars beneath the frame viewer — everything between them runs in slow motion; everything outside it plays at regular speed.
6. Tap Done, then choose Save Video or Save Video as New Clip to keep your original untouched.

The black-bar trick is the one you’ll use most often. A single clip can switch between normal and slow-motion multiple times if you adjust where the bars sit, so you can keep the dramatic entry while speeding up the rest.

Speeding Up or Slowing Down Any Video With iMovie

Normal videos — the ones shot in standard 30 or 60 fps mode — don’t show the speed controls in Photos. Apple’s free iMovie app fills that gap, and it is already available to download if you don’t have it.

1. Open iMovie on your iPhone and tap Create Project, then Movie.
2. Select the video clip you want to edit and tap Create Movie at the bottom.
3. Tap the video clip in the timeline to select it.
4. Tap the Speed button (it looks like a speedometer icon) near the bottom toolbar.
5. A yellow speed bar appears at the bottom of the clip — drag it left to slow down or right to speed up.
6. Tap Done, then tap the Share button (the square with the arrow) and choose Save Video to export the edited clip to your Camera Roll.

This workflow applies the speed change to the entire clip. iMovie doesn’t let you apply a variable speed to a single segment of a non-Slo-mo video — for that, you would use a third-party editor like CapCut.

When Photos Won’t Let You Change Speed

Most people try the Edit screen in Photos first. If the Video button or the Playback Speed option is missing, the clip was not shot in Slo-mo mode. That is Photos only surfaces speed controls for Slo-mo recordings. For standard 1080p or 4K footage, head to iMovie instead — no special settings required.

Speed Editing Options Compared

What Third-Party Apps Add That Apple’s Tools Don’t

Apple’s free methods are reliable, but they treat a video clip in one piece — speeding up or slowing down the whole thing. Third-party editors like CapCut let you vary the speed within a single shot, creating a smooth ramp from fast to slow or back again. CapCut supports playback speed from 0.1x up to 100x and includes a Curve Speed mode that speeds up gradually rather than all at once.

Apps like Video Speed Changer – Editor cut the complexity even further — you import a clip, drag a slider, and export. No timeline, no project setup, no extra learning. The tradeoff is that free apps often export with a watermark or limit resolution, so check the description before downloading.

Common Mistakes That Waste Time

The most frequent error is expecting the Photos app to handle normal videos. The speed control in Photos only appears for Slo-mo clips. If you are editing a standard 4K video and the Playback Speed option is grayed out, iMovie is your next stop — not a second tap on the same button.

Another slip happens in iMovie: speed adjustments only apply inside a project. You have to tap Share and Save Video to export the edited clip back to your Camera Roll. Without that export step, the project stays inside iMovie and the original video remains unchanged.

Apple’s iPhone user guide for trimming and speed lays out the exact Photos workflow. The iMovie speed instructions are also on Apple’s support site with step-by-step screenshots.

Which Tool Should You Use?

The right choice depends on how much control you need. For a single Slo-mo clip, the Photos app handles it in seconds. For any standard video, iMovie is free and Apple-official. And if you want creative speed effects, a third-party app adds the flexibility the built-in tools leave out — at the cost of a watermark or a one-time purchase.