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Lizely

Video Trimmer

Trim a bounded section from a local video and download a finite-duration WebM clip without uploading the source.

Privacy: your files never leave your device. All processing happens locally in your browser.

How to use

  1. 1.Choose one supported local video and wait for its duration to populate.
  2. 2.Enter start and end times in seconds, keeping the range inside the source duration.
  3. 3.Select Trim video, review the reported clip duration, and download the WebM file.

About Video Trimmer

Video Trimmer creates a new WebM clip from a selected time range in a local video. The source stays in the current browser tab and is never uploaded to Lizely. Choose a supported file, wait for its duration to load, enter start and end times in seconds, then trim and download the result.

The tool accepts MP4, WebM, MOV, M4V, and Ogg containers up to 500 MiB. The decoded source must be no longer than five minutes, no wider or taller than 4096 pixels, and no greater than 3840 × 2160 pixels in total area. A familiar extension does not guarantee success because the current browser must decode the codecs inside the container.

Start and end values may contain milliseconds. The start must be zero or greater, the end must be later than the start and no later than the decoded duration, and the selected clip must be at least 0.1 seconds. Eight independent range fixtures cover zero-based, middle, fractional, tail, and five-minute boundaries. Invalid or reversed ranges fail visibly instead of being guessed or clamped.

Trimming is performed by seeking the media element to the requested start, capturing the browser-exposed media stream, and recording until the requested end. It is a real-time re-encode, not packet-level lossless cutting. Output is WebM using a codec selected from the browser's supported VP9, VP8, and optional Opus combinations. Dimensions are preserved, while quality, keyframes, color metadata, audio layout, and file size may differ from the source.

Because MediaRecorder samples playback time and does not expose frame-accurate editing, the last encoded frame can land a small fraction around the requested boundary. The generated WebM receives the selected duration in its Segment Info so compatible players report a finite timeline. The UI reports the requested duration and output size, and Cancel stops active work.

The tool does not bypass DRM, fetch remote media, remove watermarks, preserve every metadata field, or promise professional frame accuracy. Use only video you own or have permission to edit. For broadcast delivery, exact keyframe cuts, subtitle preservation, multitrack audio, long footage, or a required MP4 codec, use a dedicated desktop editor and inspect the exported timeline.

Methodology & sources

Validate the local file and decoded metadata, parse bounded decimal start/end seconds, seek to the requested start, capture the media element stream, require a video track, select the first supported VP9/VP8 WebM recorder configuration, record during playback until the requested end, reject empty output, patch the WebM Segment Info with the selected duration using the shared audited writer, and manage the result through a revocable Object URL.

Frequently asked questions

Is my video uploaded?
No. Decode, seek, stream capture, recording, and download generation happen in the current browser tab.
Is the cut frame-accurate?
No. Browser playback capture is designed for convenient local trimming, and the encoded boundary may differ by a small fraction of a second.
Why is the result WebM?
The tool uses built-in browser MediaRecorder codecs to avoid a large media dependency and server processing.
Why does a supported extension still fail?
The browser must support the actual codecs inside the container, not only recognize its filename.

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