What is Video Frame Rate Changer?

Video Frame Rate Changer converts your video to a different FPS. It's useful for matching platform requirements, creating slow-motion or speed-ramp effects, and reducing file size. Processing happens on your device with ffmpeg.wasm, so your footage stays private.

Under the hood, the tool re-encodes your clip with libx264 using the H.264 codec. You pick one of two modes: Keep duration holds the clip at its original length and synthesises or drops frames, while Change speed re-times playback so every frame survives and the clip runs faster or slower. In Keep duration mode you choose how frames are made — Duplicate repeats or drops whole frames, Blend averages adjacent frames, and Motion uses motion-compensated interpolation for the smoothest result. A quality preset maps to a libx264 CRF value so you can trade file size against visual fidelity. Audio is copied untouched when the length is preserved, and time-stretched with pitch preserved when you change speed. Input can be MP4, WebM, MOV, AVI, MKV, FLV, WMV or M4V; the output is MP4 (MOV stays MOV).

How to use

1. Upload a video file — MP4, WebM, MOV, AVI, MKV, FLV, WMV or M4V are all accepted.
2. Pick a target frame rate from the presets — standard rates (24, 25, 30, 48, 60 fps) or broadcast and cinema rates (23.976, 29.97, 50, 59.94, 120 fps) — or type in a custom value.
3. Click Convert, then download the re-timed video.

When to use

• Lowering a 60 fps screen recording to 30 fps before uploading to a CMS with size limits.
• Matching mixed footage from a phone (30 fps) and a camera (24 fps) before editing.
• Cutting file size for an email attachment by halving the frame rate of an explainer clip.

Result

Your 60 fps gaming clip needs to be 30 fps for a client's broadcast deliverable. Select 30 fps, convert, and the timeline stays the same length with every other frame dropped cleanly.

FAQ

Does lowering the frame rate make my video shorter?

It depends on the mode. In Keep duration mode the length stays exactly the same — ffmpeg drops frames (60 to 30 fps keeps every other one) or duplicates them (24 to 30 fps doubles some up), and audio stays in sync. In Change speed mode the clip is deliberately re-timed, so raising the rate makes it shorter and faster while lowering it makes it longer and slower; the audio is stretched to match with its pitch kept intact.

Will converting from 24 fps to 60 fps make motion look smoother?

It can, depending on the interpolation method you pick. Duplicate just repeats frames so motion still steps in the original cadence. Blend averages neighbouring frames for a softer look. Motion uses motion-compensated interpolation to synthesise new in-between frames, which gives the smoothest result at the cost of much slower encoding.

Why is the output file bigger even though I lowered the frame rate?

Re-encoding always changes the bitrate, and the encoder defaults can sit at higher visual quality than your source. Pick the Smallest quality preset to push CRF higher and shrink the file, or run the result through a video compressor afterwards.

What frame rate should I use for Instagram or TikTok?

Both platforms accept 30 and 60 fps. 30 fps is the safer pick for compatibility and smaller files; 60 fps looks better for fast motion (sports, gaming) but doubles the bitrate the platform stores.

Is there a limit to how large a video file I can process?

The whole file loads into memory on your device, so practical limits sit around 1–2 GB on a typical laptop. Phones cap out lower. If processing hangs, trim the clip first or switch to a device with more available RAM.

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