How to Trim a Video at Exact Start and End Times

Fast — no re-encode copies the existing video and audio streams into the result. Avoiding a full encode is usually quicker and does not introduce another lossy encoding generation. The tradeoff is boundary accuracy: Fast cuts can snap to the nearest keyframe, so the visible beginning may not be exactly where you entered it.

Compressed video uses occasional complete keyframes and dependent frames between them. A copied segment must start where its frames can be decoded, which is why stream-copy trimming may include a little earlier material or otherwise shift a boundary. It is suitable for rough removal of an intro, outro, or long unwanted section where a nearby keyframe is acceptable.

Precise — re-encode decodes and creates the selected segment again. The tool uses H.264 video, AAC audio at 128 kbps, a veryfast preset, CRF 23, and MP4 fast-start layout. Re-encoding takes more time and changes the encoded media, but it can follow requested cut points more closely.

After you choose a file, play it in the Video panel and watch for the first frame you want to retain. Pause there and select Set start to current position. Move to the last point you want to keep and select Set end to current position. These buttons copy the preview player's current time into the range.

You can also drag both handles on the Trim range slider or edit Start and End directly. The fields accept seconds such as 83.5, minutes and seconds such as 1:23.5, and an hours form such as 01:02:03. The hints show Use seconds or m:ss.s, and an invalid boundary must be corrected before processing.

Start must be before End and both must stay within the detected duration. The Selected length readout shows the retained duration. Leave a small visual or audio margin when a hard cut would clip a word, transition, or movement.

Choose the mode based on the result you need, not only the processing time. Previewing the output is especially important in Fast mode because keyframes determine the practical start boundary.

Output depends on both the source name and the selected mode. A WebM source remains WebM in Fast mode because its existing streams are copied. Precise WebM cuts are saved as MP4 because the browser engine uses its supported H.264 encoder for precise output; the interface displays this note when relevant.

Other sources produce MP4 output in both modes. That includes common MP4, MOV, and M4V inputs, as well as accepted formats such as MKV or AVI. Fast mode still copies the streams, so the .mp4 container does not guarantee that every older device supports the codecs originally stored in an unusual source.

Precise mode creates a defined H.264 and AAC combination in MP4, which can be easier to use in common players. If your goal is primarily a smaller file rather than a shorter duration, use the video compressor after deciding which section you actually need.

The first run downloads the video engine, about 32 MB, from a CDN. A Progress panel shows Downloading video engine before trimming begins, and later jobs can use the cached engine. Clearing browser storage, changing browsers, or using a private session may require another download.

FFmpeg processing happens on your device and can be canceled. Speed and memory use depend on the video, selected mode, duration, resolution, codecs, browser, and hardware. Large files can be slow and may exhaust browser memory even though the file picker allows up to 2 GB.

Keep the page open during processing and avoid putting a memory-constrained device under extra load. Fast mode generally avoids the heavier encode, while Precise mode must process the retained video and audio into new streams.

Play the Result from several seconds before each boundary. Check that the first spoken word or visual action is intact, the ending is not abrupt, audio remains synchronized, and the result plays in your intended app. A timestamp that looks correct numerically can still feel wrong in motion.

If Fast mode starts too early, switch to Precise mode rather than repeatedly nudging the value by tiny amounts. If the precise result is larger than expected, remember that trimming shortens duration but does not offer quality or resolution controls. Compression is a separate step.

Fast mode copies streams and may snap to a keyframe. Precise mode re-encodes to follow the selected range more closely. Enter times as seconds, m:ss.s, or hours form, or use Set start to current position and Set end to current position.

A Fast WebM cut stays WebM; Precise WebM and other accepted sources are saved as MP4. The work remains in your browser, with an approximately 32 MB engine download on first use.