Does trimming re-encode the video?

When you use copy-stream mode (the default), the video and audio tracks are copied without re-encoding. This is near-instant and preserves original quality. If your trim points fall between keyframes, the actual cut may be a few frames off — re-encode mode fixes this at the cost of processing time.

Which input formats are supported?

ffmpeg.wasm can read most common containers: MP4, WebM, MOV, MKV, and AVI. MP4 and WebM are the most reliably supported across all browsers.

What format is the trimmed output?

The output is always MP4 (H.264 + AAC). If the source uses a codec that MP4 does not support, ffmpeg.wasm will attempt to transcode it automatically.

Why is my trim slightly off?

In copy-stream mode, FFmpeg can only cut at keyframes (I-frames). If your start time falls between two keyframes, the cut snaps to the nearest keyframe before it. Switching to re-encode mode gives frame-accurate cuts at the cost of speed.

Is my video uploaded during trimming?

No. ffmpeg.wasm runs entirely inside your browser. The video file is read from your local disk into browser memory and processed there. Nothing is transmitted over the network.

How long does trimming take?

Copy-stream trim finishes in seconds regardless of video length. Re-encode trim takes proportionally longer — roughly 1–5 minutes per minute of video on a modern laptop, depending on resolution and codec.

What is the maximum video size I can trim?

The limit is your available browser memory. Most devices handle files up to a few hundred MB. Very large files (over 1 GB) may cause the tab to run out of memory on low-RAM devices.

Can I trim audio-only files?

This tool is designed for video files. For audio trimming, use the dedicated Audio Trimmer at /audio/trim/ which provides a visual waveform and precise timing controls.

Video Trimmer

Cut any video to exact start and end points — entirely in your browser, no server, no upload.

100% client-side · no upload

Video file (MP4, WebM, MOV…)

Load a video file to begin.

How to trim a video in your browser

Choose your video file using the file picker. MP4 and WebM work best.
Enter the start time and end time for the clip you want to keep. Use seconds (e.g. 30) or MM:SS format.
Choose Copy streams for instant output or Re-encode for frame-accurate cuts.
Click Trim video and wait for ffmpeg.wasm to process.
Download the trimmed MP4 using the button that appears.

Common use cases

Remove intro/outro: Cut the first and last few seconds from a recording.
Extract a highlight clip: Pull a specific moment from a longer video for social media.
Split a long recording: Trim different segments from one take and download each separately.
Trim before compressing: Remove unwanted sections first, then use the Video Compressor to reduce file size.

Related tools: Video Compressor · Video Muter · Video Converter · Video to GIF

常见问题

Does trimming re-encode the video?: When you use copy-stream mode (the default), the video and audio tracks are copied without re-encoding. This is near-instant and preserves original quality. If your trim points fall between keyframes, the actual cut may be a few frames off — re-encode mode fixes this at the cost of processing time.
Which input formats are supported?: ffmpeg.wasm can read most common containers: MP4, WebM, MOV, MKV, and AVI. MP4 and WebM are the most reliably supported across all browsers.
What format is the trimmed output?: The output is always MP4 (H.264 + AAC). If the source uses a codec that MP4 does not support, ffmpeg.wasm will attempt to transcode it automatically.
Why is my trim slightly off?: In copy-stream mode, FFmpeg can only cut at keyframes (I-frames). If your start time falls between two keyframes, the cut snaps to the nearest keyframe before it. Switching to re-encode mode gives frame-accurate cuts at the cost of speed.
Is my video uploaded during trimming?: No. ffmpeg.wasm runs entirely inside your browser. The video file is read from your local disk into browser memory and processed there. Nothing is transmitted over the network.
How long does trimming take?: Copy-stream trim finishes in seconds regardless of video length. Re-encode trim takes proportionally longer — roughly 1–5 minutes per minute of video on a modern laptop, depending on resolution and codec.
What is the maximum video size I can trim?: The limit is your available browser memory. Most devices handle files up to a few hundred MB. Very large files (over 1 GB) may cause the tab to run out of memory on low-RAM devices.
Can I trim audio-only files?: This tool is designed for video files. For audio trimming, use the dedicated Audio Trimmer at /audio/trim/ which provides a visual waveform and precise timing controls.

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