How to trim a video on Android
Trimming the ends off a video is built into most phones and takes seconds. Cutting a piece out of the middle is a different job, and it is where the built-in tools stop and the quality question starts.
Trimming the ends, which your phone already does
Cutting time off the start or the end needs nothing installed.
- Open the video in Google Photos or your gallery.
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Tap Edit, then drag the handles at each end of the strip.
The strip along the bottom is the whole video. Pull the left handle in to move the start, the right one to move the end.
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Save a copy.
Take the option that saves a copy rather than the one that overwrites, at least until you have watched the result. The original is not recoverable once it is gone.
That covers a long run up at the start and the few seconds at the end where you were reaching for the button. It does not cover anything in the middle.
Cutting a piece out of the middle
This is the job the built-in editors do not do. Two handles can only keep one continuous stretch, so removing something from the middle means splitting the video into pieces and dropping one.
The move is the same wherever you do it. Put the playhead at the point where the unwanted part begins and split. Move to where it ends and split again. You now have three pieces, and you delete the middle one. What you want from the tool is to see what you are about to remove before it goes, and an undo for when the cut lands in the wrong place.
The quality question, and when it applies
Video is stored in compressed form, and re-compressing it loses a little each time. Whether a trim costs you anything depends on which of two things happens.
- A cut that copies the stream through. If the cut lands on a keyframe, the pieces can be copied without decoding and re-encoding, so the result is identical to the original. It is also close to instant, because nothing is being recalculated.
- A cut that re-encodes. If the cut has to land between keyframes, the video is decoded and written out again, which takes real time and loses a little quality.
In practice you notice this as speed. A trim that finishes immediately did not re-encode. One that shows a progress bar for a minute did. Neither is wrong, and for a single trim the loss is not something you will see.
Sound, which is usually the real problem
A great deal of "how do I edit this video" is actually about the audio: wind across the microphone, a conversation in the background, or music that should be under it instead.
Muting is the simple case and most editors have it. Turning the original down rather than off is better when there is something worth hearing underneath. Laying a track over the top brings in a question worth knowing about before you post anything: music you did not make is somebody's copyright, and the platforms match it automatically. Using a song off your phone in something you send to a friend is one thing, and putting it on a public account is another.
Watermarks, sign-ins and the rest
Most video editors on Android are built to convert you into a subscriber, and the two levers are a watermark across your video and an export limit. Both are applied at export, which is the worst moment to find out, because the editing is already done.
It is worth exporting one short test clip before you put half an hour into a project, so you learn what the finished file looks like while you still have nothing invested in it.