Frame interpolation

Frame Interpolation Apps for iPhone: How to Choose (and What to Avoid)

Search the App Store for “smooth slow motion” or “60fps” and you’ll get dozens of apps. Many of them only change playback speed or the frame rate number, and they don’t generate a single new frame. This guide gives you the checks that separate real frame interpolation apps from the rest. It then compares the main options as of October 2026 and suggests which kind of tool fits which goal. I make one of these apps, so I’ve tried to be specific about where it isn’t the best pick.

Published October 18, 202611 min read

What a frame interpolation app does (and what else it’s called)

A frame interpolation app looks at two neighboring frames, estimates how everything moved between them, and generates a new frame for the moment in between. You can use those extra frames in two ways. You can raise the frame rate at the same length, for example turning 30fps into 60fps. Or you can stretch the clip into slow motion without it turning choppy. How the different methods work, and where they fail, is explained in what frame interpolation is.

Apps describe this with different words: frame interpolation, motion interpolation, optical flow, smooth slow-mo, AI slow motion, or the name of a model such as RIFE. On TVs and video players it’s often called MEMC (motion estimation, motion compensation). They all mean the same basic thing: new frames are generated from estimated motion. If you want the full explanation of duplicated vs. generated frames, see how to convert 30fps to 60fps on iPhone.

7 things to check before you download (or pay)

1. Does it actually generate in-between frames?

This is the big one. Plenty of “slow motion” apps just slow playback down, which means each existing frame stays on screen longer. Slow a 30fps clip to half speed that way and you see only 15 distinct frames per second, and it looks choppy. iMovie on iPhone works like this: it can slow clips down (to as little as 1/8 speed in Storyboard and Magic Movie projects, per Apple), but it doesn’t generate in-between frames. Look for explicit wording in the App Store description, such as “frame interpolation,” “optical flow,” “RIFE,” or “generates new frames.” Words like “speed” and “fps converter” alone aren’t enough.

2. Can you export a file?

Some apps are video players that interpolate in real time while you watch. SVPlayer, for example, is a player that uses the SVP engine to convert video to 60fps or higher as it plays, according to its App Store listing. That’s great for watching movies more smoothly. But if you want to post the clip, send it, or edit it, you need an app that writes the result to a new video file.

3. On-device or upload?

Online AI services do the work on their servers. That means uploading your video, waiting, and downloading the result, usually with file-size or length limits, and it means trusting their data handling with your footage. On-device apps skip all of that and work offline. Recent iPhones are fast enough to run interpolation models locally, so on-device is now common. It isn’t unique to any one app.

4. What does the free tier really let you test?

Before paying, you want to see the result on your own footage. Check three limits: length (how many seconds can you process for free?), watermark (is the preview or the saved file marked?), and saving (can you save anything at all, or only preview?). A free tier that lets you judge the quality on a real clip is worth more than a long feature list.

5. Subscription or one-time purchase?

Look at the “In-App Purchases” list on the App Store page, not just the word “Free” at the top. Weekly subscriptions are common in this category. Some apps offer a lifetime option next to their subscriptions. If you only need to fix a few clips a year, a weekly or monthly plan you forget to cancel can cost more than you expect.

6. Frame rate and slow-down options

Match the options to what you need. Do you want 60fps, 120fps, or 240fps output? Only 2× and 4× slow motion, or custom speeds and speed curves for velocity edits? How is audio handled in slow motion? Apps differ a lot here.

7. Can you compare before you save?

Interpolation sometimes warps fast-moving edges, text, or thin lines. A side-by-side or split-screen comparison lets you catch that before you save. Otherwise you’re flipping between two files in Photos.

The kinds of tools that “make video smoother”

CapCut’s smooth slow-mo

CapCut’s US App Store description says you can “create smooth slow-motion with the optical flow feature and speed curve tool.” That is frame interpolation, so if you already edit in CapCut, it’s the obvious first thing to try. Whether it’s free is less clear. CapCut’s own help content describes its speed tools as free, but users have reported smooth slow-mo becoming a Pro feature. As of October 2026 it may depend on region, timing, or account, so check whether a Pro badge appears in your app. CapCut’s paid plans are subscriptions. We cover this in detail in CapCut smooth slow-mo: is it free, and what are the alternatives?

Online services and desktop software

Online AI tools can be convenient for a one-off clip, but read their limits, watermark rules, and privacy terms before uploading. Desktop software is still the strongest option for long videos, batches, and fine control, if you have the computer for it. Flowframes, a popular free tool, is Windows-only. Mac users have other options, covered in Flowframes for Mac? Your options.

Dedicated frame interpolation apps for iPhone, compared (October 2026)

Everything in this table comes from each app’s US App Store listing, checked on October 18, 2026. Listings change, so check the current page before you buy. I’ve listed pricing models but not prices.

Minimum iOS versions: Time Cut iOS 13, PixelJex iOS 17.6, SlowCam iOS 26, FrameFlo iOS 16, SVPlayer iOS 16. To find them on the App Store, search for “Time Cut: Smooth Slow Motion,” “AI Video Smoother: 120FPS” (PixelJex), “SlowCam - Create SloMo Videos,” and “SVPlayer - watch in 60+ fps.”

A few notes for context. Time Cut is the most established of these, with about 15,000 US ratings, and has the broadest set of speed and frame rate tools. Its listing was last updated in February 2025. SlowCam is new and has very few ratings, but it’s free and does exactly one job. SVPlayer’s listing says high-quality conversion, such as with RIFE, needs a desktop computer running SVP 4.

What FrameFlo does and doesn’t do

Since I make it, here are its limits plainly. FrameFlo tops out at 120fps, with no 240fps. Slow Motion is 2× or 4× only, with no custom speeds or speed curves. It’s built for frame interpolation only, so for cuts, effects, or speed ramps you’ll still want an editor. In Slow Motion, the original audio plays at normal speed from the start, so it won’t match the slowed video and goes silent after the original length. SlowCam, for comparison, time-stretches the audio. It doesn’t improve sharpness, noise, or shake. And neither RIFE nor on-device processing is unique to it.

What it does offer: Pro is a one-time purchase and there’s no subscription at all. See the App Store for the price. The free version lets you convert clips up to 10 seconds (or the first 10 seconds of a longer clip) to 60fps and save the result, at Low export quality. You can also create and preview 2×/4× slow motion for free (saving it needs Pro). A split slider lets you compare the original and the result on one screen before saving.

Best frame interpolation app for iPhone? Picks by goal

• You already edit in CapCut and want a slow-mo moment: try CapCut’s smooth slow-mo first. If it’s locked behind Pro for you, come back to the list below.
• You want 240fps, speed curves, velocity edits, or motion blur: Time Cut lists all of these. FrameFlo doesn’t offer them.
• You just want free 2× or 4× slow motion and you’re on iOS 26: SlowCam is free with no in-app purchases listed (October 2026).
• You want to make clips 60fps or 120fps at the same length: FrameFlo and PixelJex both do this on-device. FrameFlo lets you save 10-second 60fps results for free and compare them in a split view before saving. PixelJex adds 90fps and GIF interpolation.
• You hate subscriptions: FrameFlo is one-time purchase only. Time Cut and PixelJex also list one-time options next to their subscriptions.
• You want to watch movies smoother, not export: a motion-smoothing player such as SVPlayer.
• Long videos, batches, or interpolation plus upscaling: desktop software. See your options on a Mac, or Flowframes on a Windows PC.
• Analyzing a golf swing or other technique: generated frames are estimates, so they make motion look smooth but aren’t measurements. Record in Slo-mo when you can. See smooth slow motion for golf swings.

Red flags

• “60fps” that finishes instantly. Generating frames takes computation. A near-instant result usually means frames were duplicated. You can check by playing fast motion side by side.
• No way to see the result before paying. If the app asks you to subscribe before showing you anything, you can’t judge the quality.
• A subscription required just to save. Not a dealbreaker on its own, but compare it with how often you’ll actually use the app.
• Interpolation as a footnote. If an app’s main pitch is something else (effects, filters, “enhance”), test its interpolation on a fast-motion clip before relying on it.
• Vague upload terms. For online tools, look for a clear statement of how long your video is kept and what it’s used for.

FAQ

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.