A useful recording can begin with several seconds of preparation and end after the relevant action has finished. QuickTime Player can trim those ends. Preserve the full recording first, because a short excerpt can accidentally remove the detail that explains what happened.

Create a clearly named working copy in Finder and open that copy in QuickTime Player on Mac. Watch the full section you intend to keep, including its audio. Note a start point before the important action and an end point after the result becomes clear.

Choose boundaries that retain the story

Choose Edit, Trim and drag the yellow handles around the portion to keep. Content outside the handles will be removed. Apple documents holding a handle to inspect individual frames when you need a more precise boundary.

Leave a small amount of useful context around a demonstration. For example, a clip showing an error should include the action that triggers it and enough time to read the message. Starting directly on the error may conceal whether it appeared before or after the attempted step.

Click Trim when the range is correct and save the working result under its delivery name. If the save workflow asks for a new location or name, check both before accepting so the shortened copy stays distinguishable from the full recording.

Review the actual saved excerpt

Close and reopen the delivery file. Play its first and last few seconds, then watch the complete excerpt with sound. Check that a spoken sentence is not cut in half and that the final frame does not disappear before the viewer can read it.

Trimming the ends does not hide private material that remains in the middle. Review the entire retained area, including notifications, filenames and any background speech. Use an appropriate editing workflow if internal content needs removal.

Keep the full recording until the excerpt is accepted. Record the excerpt’s purpose and filename in the handover note, especially when several similar clips exist, so the recipient receives the intended explanation rather than an earlier trial.

References: Apple: trimming QuickTime movies, Apple: saving edited clips.