Trim Video

Q: Is my video uploaded to a server?

No. The video is processed entirely in your browser via ffmpeg.wasm (WebAssembly). The site operator never sees the contents. Only the ffmpeg library itself (~32MB) is downloaded on first use; the video itself never leaves your device.

Q: What's the difference between Fast and Precise mode?

Fast mode keeps the original codec (no re-encoding) and finishes a 1GB video in seconds to tens of seconds. The catch: cuts are aligned to H.264 keyframes (typically 1 to 5 seconds apart), so a timestamp between keyframes snaps to the nearest one. Precise mode cuts exactly at the requested timestamp by re-encoding to H.264 — slower (about 0.3 to 1× the clip duration).

Q: How do I enter the times?

HH:MM:SS, MM:SS, or seconds — all three formats work. Examples: 1:23:45 (1 hour 23 minutes 45 seconds), 4:30 (4 minutes 30 seconds), 90 (90 seconds). Decimals are allowed — 90.5 means 90.5 seconds.

Q: What is the output format?

Output is always MP4 (H.264 + AAC) — playable on virtually any device or messaging app. Fast mode just rewraps the existing codec into MP4 even if the input wasn't H.264/AAC.

Q: How long does it take?

Fast mode: independent of file size — even a 1GB video usually finishes in seconds to tens of seconds. Precise mode: about 0.3 to 1× the trimmed clip's length on desktop Chrome. Mobile is 2 to 3 times slower due to the single-thread limit.

Save just the segment you want by start and end times — Fast mode finishes in seconds.

Your video never leaves your browser. All processing happens locally via ffmpeg.wasm (WebAssembly).

First use: the video processing engine (ffmpeg.wasm, ~32MB) downloads automatically. Wi-Fi recommended. After that, it's cached and starts instantly.

📱 Mobile: we recommend videos at 720p or below and under 1 minute — for larger files, desktop Chrome is more reliable.

Drag a video file here, or click to choose

MP4 · MOV · WebM · MKV · AVI — recommended ≤ 500MB (mobile) / ≤ 1.5GB (desktop)

Start time

End time

Mode

Fast mode is enough for most cases. Use Precise only when the start time has to land exactly.

Which mode to pick?

Situation	Recommended mode	Why
Quick clip from a large video	Fast	Even 1GB finishes in seconds. ±1~5 second alignment is acceptable.
Lecture / interview — exact speech segment	Precise	Frame-accurate cut even between keyframes
Multiple clips of identical length	Precise	Fast mode result lengths can vary slightly with keyframe alignment
Social / messenger attachment	Fast	Speed wins; 1~2 second drift is irrelevant

Related tools

Why does Fast mode sometimes miss the start time?

Codecs like H.264 use keyframes (I-frames) as independent reference frames; the rest are stored as differences from neighbors. Cutting without re-encoding only works at keyframe boundaries (typically 1 to 5 seconds apart) — otherwise the output breaks. In Fast mode, your start point may snap back to the nearest preceding keyframe.

Can I close the page mid-process?

Closing the page cancels the in-progress job. The downloaded ffmpeg library stays cached, so the next visit reuses it without redownloading.

Why isn't multi-threaded (faster) processing supported?

Static hosts like GitHub Pages can't set Cross-Origin-Opener-Policy / Cross-Origin-Embedder-Policy headers, which disables SharedArrayBuffer. This mostly affects Precise mode (re-encoding on a single thread); Fast mode skips decoding so the impact is small.

Frequently asked questions

Is my video uploaded to a server?

No. The video is processed entirely in your browser via ffmpeg.wasm (WebAssembly). The site operator never sees the contents. Only the ffmpeg library itself (~32MB) is downloaded on first use; the video itself never leaves your device.

What's the difference between Fast and Precise mode?

Fast mode keeps the original codec (no re-encoding), so even a 1GB video finishes in seconds to tens of seconds. The catch: cuts are aligned to H.264 keyframes (typically 1 to 5 seconds apart), so a timestamp between keyframes snaps to the nearest one. Precise mode cuts exactly at the requested timestamp by re-encoding to H.264 — slower.

How do I enter the times?

HH:MM:SS, MM:SS, or seconds — all three formats work.
Examples: 1:23:45 = 1 hour 23 minutes 45 seconds / 4:30 = 4 minutes 30 seconds / 90 = 90 seconds. Decimals are allowed — 90.5 means 90.5 seconds.
You can also use the buttons that copy the current playback position from the source preview into start/end fields.

What is the output format?

Output is always MP4 — playable on virtually any device or messaging app. Fast mode just rewraps the existing codec into MP4 even if the input wasn't H.264/AAC.

How long does it take?

Fast mode: independent of file size — even a 1GB video finishes in seconds to tens of seconds. Precise mode: about 0.3 to 1× the trimmed clip's duration on desktop Chrome. Mobile is 2 to 3 times slower.

Can it handle large videos?

On desktop Chrome, around 1 to 2GB. Mobile browsers may become unstable above ~500MB due to memory limits.

References

Last verified: 2026-05-05 / Powered by ffmpeg.wasm (WebAssembly).

ffmpeg.wasm — official site (BSD/LGPL)
Seek options (-ss, -to, -c copy) — FFmpeg Wiki: Seeking
Keyframes (I-frames) — H.264/AVC standard ISO/IEC 14496-10

⚠️ For personal use only. Respect copyright when working with videos you don't own.