How to add captions to a video on your phone (size, outline, position)
More than half of Shorts and Reels are watched with the sound off. One line of text is often the difference between someone watching to the end and scrolling past. The catch is that captioning on a phone is more tiring than it should be: text too small to read, white text lost on a bright background, or the caption hidden under the app's own UI. This guide covers the two caption formats and the size, outline and position rules that keep text readable.
Burned-in captions vs subtitle files
There are two kinds of captions. Burned-in captions are drawn into the video pixels, so they show up in any app or social network. Subtitle files such as SRT are separate, and can be toggled on and off only where the platform accepts them, such as YouTube.
Shorts, Reels, Stories and messenger sends do not accept subtitle files, so on a phone burned-in is the default. The trade-off is that once saved, the text cannot be removed, so catch typos before exporting. SnipCut captions are burned in, and you can edit the text freely right up until you save.
Size and outline that stay readable
The first reason captions are unreadable is size. The editor shows the frame large, which fools you; in an actual feed, text under about 5% of the screen width is barely legible. A good rule is a size that fits roughly 25-30 Latin characters (12-15 CJK characters) on one line. Anything longer should wrap or be split into two captions.
The second reason is contrast. Brightness changes from scene to scene, so color alone is not enough; you need an outline or a shadow. White text with a black outline reads on any background and is the safest default. Change only the word you want to emphasise to a color like yellow.
Positions that avoid app UI
Every app covers the top and bottom of a 9:16 video with its own interface. Shorts and Reels put the title, account and buttons over roughly the bottom 20%, and the status bar and tabs take the top 10%. The safest spot for a caption is 60-75% down the frame, slightly below center. For 16:9 landscape video, leave the bottom 10% empty and place the caption just above it. Play it back once to make sure you are not covering a face or a hand gesture.
How many captions, and for how long
Two to four seconds per caption is the sweet spot. Under one second disappears before it is read; over six seconds makes the video feel frozen. Break by sentence to match the speaking pace, and keep one caption on screen at a time. If it feels like too much text, the fix is fewer characters per caption, not fewer captions.
- Open the video in SnipCut, scrub the playhead to where the caption should start, and tap '+ add caption'
- Type the text, choose white with a black outline, and size it so about 25-30 characters fit on one line
- Drag the caption to 60-75% down the frame, play it back once, then Save — the caption is burned into the video
A caption in 3 seconds
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