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Processing:Local only Scope:One clip Source:{{ formatDuration(params.source_duration) }}
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Maximum 80 MiB, 5 minutes, and 1920 × 1080. Use the demo clip to try the complete workflow.
The demo is generated on this device and is not downloaded from a provider.
Choose a video to review its timeline.
s
Enter seconds or use the current source playhead.
s
The selected clip is {{ selectedDurationLabel }}.
Timeline review:
Boundary precision depends on the source frame and audio timing.
Milliseconds is the neutral default; every option changes presentation only.
Video clip

The chart renderer is unavailable. The same interval values remain in Trim details.

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A useful video clip begins and ends on moments the viewer can recognize. Trimming removes material before the chosen start and after the chosen end without changing the story inside that interval. It is commonly used to cut setup time from a recording, isolate a demonstration, shorten a screen capture, or prepare a small excerpt for review.

Time values describe positions on the media timeline, not frame numbers. A start of 12.400 seconds means the first retained moment is 12.4 seconds from the beginning. The end is the first excluded moment, so an interval from 12.400 to 28.900 seconds has a requested duration of 16.500 seconds.

Container
The file wrapper, such as MP4 or WebM, that holds video, audio, timing, and metadata.
Codec
The method used to encode a video or audio track, such as AVC, AAC, VP9, or Opus.
Key frame
A self-contained video frame from which later dependent frames can be decoded. Copying encoded packets can start exactly only when the selected boundary aligns with a suitable key frame.
Transcoding
Decoding and encoding the media again. It supports more exact cuts and wider compatibility but takes longer and may change file size or visual quality.

Frame and audio timing place a practical limit on boundary precision. A player can seek to a decimal timestamp, but the visible first frame and audible first sample depend on the source timing and codec. Always preview the retained interval and the finished clip when a cut must land on a word, movement, or edit point.

How to Use This Tool:

Choose the source, mark the interval while watching it, then confirm the generated clip before downloading.

  1. Choose one browser-decodable video or load the demo clip. The source must be no larger than 80 MiB, five minutes, or 1920 × 1080.
  2. Move the source player to the first moment you want to keep and select Use playhead as start, or enter the Start time in seconds.
  3. Move to the first moment that should be excluded and select Use playhead as end, or enter the End time. The interval must be at least 0.05 seconds and cannot extend beyond the source.
  4. Select Preview interval and listen across both boundaries. Adjust the times if the cut begins mid-word, loses a transient sound, or keeps an unwanted frame.
  5. Select Trim video. If the browser cannot decode or encode the source codec, choose a supported source or retry in a current browser with media-codec support.
  6. Play the finished Video clip. Check its beginning, end, sound, duration, and output format before downloading it.

Interpreting Results:

The requested duration confirms the arithmetic of the selected interval. The playable result is the stronger check because codec timing may place the first decodable frame near, rather than exactly on, a requested packet-copy boundary. Compare the source preview with the finished clip whenever the cut is timing-sensitive.

MP4 output may contain AVC video with optional AAC audio, while compatible WebM packet trimming keeps VP8, VP9, or AV1 video with optional Opus or Vorbis audio. A different container or codec is not automatically an error. It reflects the source tracks and the processing route available in the browser.

Technical Details:

A trim interval is half-open: the start is retained and the end is the first excluded timestamp. This convention makes adjacent clips meet at one boundary without intentionally duplicating the boundary moment.

Formula Core

The requested clip length is the end time minus the start time.

tclip = tend − tstart
  • tstart is the first retained timestamp in seconds.
  • tend is the first excluded timestamp in seconds.
  • tclip is the requested duration in seconds and must be at least 0.05 seconds.

For 12.400 to 28.900 seconds, the requested duration is 28.900 − 12.400 = 16.500 seconds. Timestamp-display choices round labels only; they do not change the selected interval or encoded media.

Transformation Core

The browser selects one of two media paths after inspecting the primary video and audio tracks. The output timeline is shifted to begin at zero in either path.

Path When it applies Result Important boundary
Packet copy AVC with optional AAC for MP4, or VP8/VP9/AV1 with optional Opus/Vorbis for WebM. Keeps the compatible encoded tracks without recompressing them. The first video packet must be a verified key frame within 0.005 seconds of the requested start.
Transcode The browser exposes the needed video decoding and encoding support. Produces MP4 with AVC video and, when present, AAC audio. Processing takes longer and the re-encoded size and quality can differ from the source.

Only the primary video track and optional primary audio track are used. Unsupported codecs, undecodable tracks, missing encoded data inside a very short interval, or a packet-copy start that does not align with a key frame can stop the trim instead of returning a misleading file.

Privacy and Limits:

The source file is read and processed in the current browser tab; it is not uploaded by the trimming workflow. The media engine itself is loaded from a third-party content host, so an initial network request may still be needed before processing begins.

  • Maximum source size: 80 MiB.
  • Maximum duration: 300 seconds.
  • Maximum dimensions: 1920 × 1080.
  • Minimum retained interval: 0.05 seconds.
  • Browser codec support determines which files can be decoded, copied, or transcoded.

References: