AI Image & Video

Vertical Video (9:16) Mobile Layout Spec and Pre-Delivery Checklist

Fine on a computer does not mean fine on a phone. Always review a vertical video on a phone, inside the real app.

10/23/2026 ｜ 3 min read ｜ Numbers assume a 1080x1920 canvas; for 720x1280 multiply everything by 2/3. For Shorts, Reels and Douyin

Who this is for: anyone making YouTube Shorts, IG Reels or Douyin, whether you edit in CapCut, Premiere or with code.

1. Layout spec (numbers after testing and correction)

Element	Spec	Why
Subtitle size	70px	60px makes you squint on a phone
Characters per line	11 CJK characters at most	Beyond that, break into the next subtitle at punctuation; do not wrap into two lines on one frame
Subtitle too long	Auto-shrink the font to fit one line	Wrapping makes the eye jump back and forth
Subtitle position	Bottom of subtitle about 560px above the frame bottom	The bottom ~420px is covered by the platform’s title, channel name and buttons
Subtitle backing	Semi-transparent dark gradient band, fading in only when there is a subtitle	Readable on bright and dark backgrounds
Subtitle outline and shadow	Thin black outline plus soft shadow	Color contrast alone is not enough
Speaker name tag	104px, in the character’s own color	At 66px you cannot read it on a phone
Top label (series name, episode)	About 190px from the top, 46px, dark capsule background	Too high and the status bar or search bar covers it; without a backing it disappears on light frames
End-card channel name	Horizontal strip, text about 60px or larger	Three characters crammed into a small square are unreadable
People	15 to 20% closer than the landscape version	Too small on a phone and the emotion is lost
Right side	Keep key info about 150px clear of the right edge	Like, comment and share buttons sit there

Platform UI positions change. Each quarter, screenshot one of your own videos on a phone and confirm no new button covers the subtitles.

2. Character color rule (required for multi-person dialogue)

Give each character a main color with very different hue, one warm and one cool for example, not two dark tones.
Use that color in three places: the clothing, the name tag on the subtitle and the subtitle text color (a lighter tint of the same hue).
Use a neutral color for narration, for example cream text with a vermilion seal.
Keep one “symbol color” for the story’s key object across the whole video and do not let it collide with a character color.

3. Keep texture effects and text on separate layers

Rough edges, paper grain and aging effects go on the base image or color layer only.
Text sits on its own layer with no filter applied, so it stays sharp.
In your editor: name-tag background on one track, text on another, and effects on the background track only.

4. Phone checklist before delivery

Open the platform app and watch in the real playback UI. Tick each item:

Every subtitle fits on one line, no wrapping, nothing off-screen
Subtitles are not covered by the bottom title, channel name or buttons
The top label is not blocked by the status bar or search bar
Looking only at the name tags, without the picture, you know who is speaking
The text on name tags is clear, not a blob of color
The end-card channel name and subscribe prompt read at a glance
People are large enough to read action and emotion
Sample one frame from the darkest and one from the brightest scene; subtitles are clear in both
On mute, the subtitles alone are enough to follow the story (many people scroll on mute)

5. Prompts for an AI

For review:

These are 5 screenshots of my vertical video (1080x1920). Check each against these standards: is the subtitle at least 560px above the bottom, does it stay on one line, can I tell who is speaking, is any text blurred by an effect, is there key information in the right-hand 150px. List the problems and suggested fixes for each screenshot.

For color:

My video has [N] characters: [names and personalities]. Design a main color set for each (clothing color, name-tag background, subtitle text color as three color codes). The hues must differ clearly between characters, be readable on both dark and light backgrounds, and avoid my symbol color [color code].

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