Slow motion
How to Make a Normal iPhone Video Slow Motion After Recording
You caught the moment — a first step, a dive, a trick shot — but in regular Video mode, not Slo-mo. The good news is that you can still slow it down after recording. The catch is that most iPhone videos are 30fps, and slowing those down the usual way makes them choppy. This guide covers the three ways to do it on iPhone, which one fits your video, and how to keep the result smooth.
THE SHORT ANSWER
- Yes, you can make a normal iPhone video slow motion after recording. There are three ways: the Photos app, iMovie, or an AI frame interpolation app.
- Photos can slow down a video only if it was recorded above 30fps (for example, 60fps) and your iPhone runs iOS 18 or later. That's Apple's own rule.
- iMovie can slow down any video, but it doesn't create new frames. A 30fps clip at half speed shows only 15 frames per second, which looks choppy.
- AI frame interpolation generates the missing in-between frames, so a 30fps clip slowed 2× or 4× still plays at 30fps. In FrameFlo you can create and preview this for free; saving slow motion requires Pro, a one-time purchase.
Which method fits your video?
The right tool depends almost entirely on one number: the frame rate your video was recorded at. If you're not sure what yours is, here's how to check a video's frame rate on iPhone.
| Your video | Best option | Will it look smooth? |
|---|---|---|
| Shot in Slo-mo mode (120 or 240fps) | Photos: adjust the slow-motion section | Yes — it already has the extra frames |
| 60fps or higher, iPhone on iOS 18 or later | Photos: change the playback speed | Yes at moderate slowdowns — at half speed, 60fps still gives 30 real frames per second |
| 30fps (most everyday videos) or 24fps | AI frame interpolation | Yes — the missing frames are generated |
| Any video, if some choppiness is OK | iMovie | Depends on the frame rate (see the table below) |
If your video falls in the first two rows, you don't need another app. Use Photos.
Method 1: Slow down a video in the Photos app (iOS 18 and later)
Since iOS 18, the Photos app can change a video's playback speed. Apple's condition is specific: the video must have been "captured at a frame rate higher than 30FPS" (Apple Support).
- Open the video in PhotosThen tap the Edit button.
- Tap VideoThis shows the video editing tools.
- Tap the Playback Speed buttonThen choose a speed.
Apple notes that "the playback options available depend on the format of the video you captured" — the higher the recording format, the more options you get. The steps are the same in Apple's iPhone User Guide for iOS 18, iOS 26 and iOS 27.
There are two catches. First, a standard 30fps video gets no speed option at all, and 30fps has long been the default in the Camera app's Video mode. If that's what you're seeing, here's why you can't slow down a video in Photos and what to do. Second, Apple doesn't describe this feature as creating new frames. For a 60fps clip that's fine: at half speed it still has 30 real frames for every second of playback.
Shot in Slo-mo mode? Those videos are already slow. Open the video, tap Edit, and drag the vertical bars under the frame viewer to choose which part plays in slow motion.
Method 2: iMovie — works on any video, but adds no frames
iMovie, Apple's free editing app, can slow down any clip, including 30fps ones. The iMovie slow motion guide has every step and the numbers by frame rate. In a movie project:
- Tap the clip in the timelineThe inspector opens at the bottom of the screen.
- Tap the Speed buttonA yellow bar appears under the clip.
- Drag the slider leftThe relative speed appears below the clip — 1/2x means half speed.
In Storyboard and Magic Movie projects, Apple says you can go as low as one-eighth speed. By default, iMovie keeps the pitch of the audio the same when you change speed (Apple's iMovie guide).
What iMovie doesn't do is create new frames. Apple's documentation describes no frame interpolation or optical flow feature; the frames you already have are simply shown for longer. That's where the choppiness comes from.
Why a slowed-down 30fps video looks choppy
Slowing down doesn't add frames. It spreads the same frames over more time. A 5-second clip at 30fps has 150 frames. At half speed it runs for 10 seconds, but it still has only 150 frames — 15 per second. As a rough rule of thumb, motion starts to look steppy below about 24 frames per second.
| Recorded at | 1/2 speed | 1/4 speed | 1/8 speed |
|---|---|---|---|
| 30fps (standard video) | 15 frames/s | 7.5 frames/s | 3.75 frames/s |
| 60fps | 30 frames/s | 15 frames/s | 7.5 frames/s |
| 120fps (Slo-mo) | 60 frames/s | 30 frames/s | 15 frames/s |
| 240fps (Slo-mo) | 120 frames/s | 60 frames/s | 30 frames/s |
The numbers are real, recorded frames per second of playback. Read across the 30fps row: half speed already drops below the comfortable range, and 1/8 speed is close to a slideshow. Now compare the 240fps row — that's why videos shot in Slo-mo stay smooth. No editor setting changes these numbers, because they're fixed by what the camera recorded. If your iPhone's Auto FPS setting dropped a low-light video to 24fps, it's even fewer: 12 frames per second at half speed. For more on frame rates, see 30fps vs 60fps vs 120fps.
Method 3: AI frame interpolation — smooth slow motion from a 30fps video
If the frames you need were never recorded, the only way to get smooth slow motion is to create them. Frame interpolation looks at two neighboring frames, estimates how things moved between them, and generates new in-between frames. Add one new frame between every pair and you have twice as many frames — enough to play the clip at half speed without dropping below 30 frames per second.
Each box is one frame of 30fps playback. When a 30fps clip is stretched, the same picture repeats, so motion moves in jumps. When it's interpolated, every slot shows a different picture.
That's how FrameFlo's Slow Motion mode works. It runs RIFE, an AI frame interpolation model, through Core ML on your iPhone. The new frames are generated from the estimated motion — they aren't copies or blends of the neighboring frames. Everything happens on the device: your video is never uploaded, and processing works even in Airplane Mode.
How to make smooth slow motion in FrameFlo
- Pick your videoOpen FrameFlo and choose a clip from your Photo Library or the Files app. The free version handles videos up to 10 seconds. For longer videos, it can process just the first 10 seconds for free.
- Look at Video InfoThe Video Info screen shows Before and After side by side: frame rate, duration, file size and output resolution, plus an estimated processing load (Light, Moderate, Heavy or Very Heavy). The Before column tells you your video's actual frame rate.
- Set Duration to Slow MotionThe other option, Same Length, adds frames without changing the length. That one is for making a video smoother at 60fps or 120fps.
- Choose Slow Down: 2× or 4×2× generates one new frame between each pair and doubles the length. 4× generates three and makes the clip four times as long. There's no Frame Rate picker in this mode: the output keeps your video's original frame rate, so a 30fps clip stays 30fps — it just gets longer.
- Check the After column, then tap Add to QueueThe duration should be 2× or 4× the original, with the same frame rate.
- Compare before and afterYou'll get a notification when it's done. Drag the split slider across the picture to compare the original with the slow-motion result.
- Save (Pro)Save to your Photo Library or the Files app. Saving slow motion requires Pro. In the free version, the button reads "Save with Pro" and the preview carries a PREVIEW watermark.
To stop the screen from locking mid-job, turn on Keep Screen Awake While Processing (available in the free version). In the free version, leaving the app interrupts processing.
The free version uses the lowest settings; Pro unlocks the rest. A higher Inference Resolution (Medium or High) lets the AI work at a larger size internally, which helps it estimate fine detail more accurately but takes more time and memory; it doesn't change the size of your output video. Export Quality sets the compression (Low, Medium or High — 3, 8 or 20 Mbps). Output Resolution can resize the video from 480p up to 4K, but that's plain resizing, not AI upscaling, so it doesn't add detail.
2× or 4×?
| Slow Down | New frames per pair | Length | Output (30fps source) | Good for |
|---|---|---|---|---|
| 2× | 1 | 2× longer | 30fps | Most clips. Start here. |
| 4× | 3 | 4× longer | 30fps | The split second you want to study, like an impact or the top of a jump |
The faster the subject moves, the more the AI has to guess, and 4× asks it to guess three frames instead of one. If 4× looks smeared on a fast subject, 2× usually holds up better.
What happens to the audio
The original audio plays at normal speed from the start. Because the picture is stretched, sound and motion won't line up, and once the original length has passed, the rest of the clip is silent. For most slow-motion clips you'll want to mute it or add music in an editor afterward.
What's free and what needs Pro
You can create slow motion for free — 2× or 4× — and compare the result with the split slider. That way you can see whether it works on your video before paying anything.
Saving slow motion requires Pro. In the free version, the save button reads "Save with Pro" and the preview shows a PREVIEW watermark.
Same Length mode (making a video smoother without changing its length) saves for free at up to 60fps; 120fps output is a Pro feature.
Pro is a one-time purchase, not a subscription — see the App Store for the price. It also removes the 10-second limit, lets you queue up to 10 videos, and keeps processing for up to about 30 seconds if you switch to another app (the most time iOS allows).
See whether your 30fps clip can become smooth slow motion — before you pay anything.
Get FrameFlo on the App StoreCreate and preview free · Saving slow motion requires Pro (one-time purchase) · iPhone with iOS 16 or later
When interpolation won't look right
Frame interpolation makes motion smoother. It doesn't fix everything, and it's better to know that before you start.
- Very fast motion. If something moves a long way between two frames, the estimate can miss, leaving smears or doubled edges. Think splashing water, flapping wings, or the head of a golf club.
- Things passing in front of other things, like a hand crossing in front of a face.
- Thin lines and fine detail: hair, the outlines of arms and legs, fences, nets.
- Text, captions and cuts between shots. Frames generated across a cut mix two unrelated scenes, so trim around cuts and process each shot separately.
- Semi-transparent things and things that appear suddenly.
- Very low frame rates, around 10fps or below.
- Image quality doesn't improve. Blur, noise, compression artifacts and camera shake stay as they are — FrameFlo doesn't stabilize or enhance video. Information lost to dropped frames can't be recovered either.
- Memory. Heavy settings can use more than 2GB of memory, so on iPhones with less memory (roughly iPhone 12 and earlier) iOS may stop the job. Lower the Inference Resolution, don't push Output Resolution too high, trim the video, or close other apps.
Next time: record in Slo-mo or 60fps
Interpolation rescues videos you can't reshoot. When you can plan ahead, recording more real frames always beats generating them.
- Slo-mo mode. By default, Slo-mo records 1080p at 240fps on the back camera and 120fps on the front. You can switch the back camera to 120fps in Settings > Camera > Record Slo-mo, and supported models also offer 4K at 120fps (Apple).
- 60fps in Video mode. In the Camera app's Video mode, tap the resolution and frame rate shown at the top of the screen and pick 60 (options depend on your model). A 60fps video can be slowed to half speed in Photos and still show 30 real frames per second. Files are larger.
For when 60fps is worth it and when 30fps is fine, see 30fps vs 60fps vs 120fps on iPhone. Filming sports? The golf swing slow-motion guide covers lighting and camera angles.
FAQ
Can you make a video slow motion after recording on iPhone?
Yes. If the video was recorded above 30fps and your iPhone runs iOS 18 or later, open it in Photos, tap Edit, tap Video, then tap the Playback Speed button. For a standard 30fps video, iMovie can slow it down but it will look choppy; an AI frame interpolation app keeps it smooth by generating new frames.
How do I make a normal video slow motion on iPhone for free?
It depends on the frame rate. A 60fps-or-higher video can be slowed in Photos at no cost. A 30fps video can be slowed in iMovie (free), but it will get choppy. In FrameFlo you can create and preview smooth 2× or 4× slow motion for free, but saving it requires Pro.
How do I slow down a video on iPhone without losing quality?
Slowing down doesn't lower the resolution — what you lose is frames per second, which is what makes slow motion look choppy. To avoid that, start from a high frame rate (Slo-mo or 60fps) or generate the missing frames with frame interpolation. Interpolation keeps the resolution unless you change it, but it won't make a blurry video sharper.
Can I make only part of a video slow motion on iPhone?
Yes, in two ways. For videos shot in Slo-mo, Photos lets you drag the vertical bars to choose the slow section. In iMovie, you can split a clip into ranges with different speeds. FrameFlo slows the whole clip, so trim it first: in Photos, tap Edit, drag the ends of the frame viewer, and choose Save Video as New Clip.
Why is my slow motion video choppy?
Because it doesn't have enough frames for the speed you chose. A 30fps video at half speed shows 15 frames per second; at quarter speed, 7.5. Recording in Slo-mo or generating in-between frames with interpolation fixes it.
Does FrameFlo upload my videos?
No. All processing happens on your iPhone, and it works in Airplane Mode. The app only goes online to show the price, make a purchase, or restore a purchase through the App Store.
Written by punimaru, the developer of FrameFlo. App details are based on how the app is actually built. Since this is my own app, I've also noted where it isn't the right tool and what else you can use.