Glossary
What is a text overlay?
By the KeyMo team · Updated
A text overlay is any writing placed on top of a video's picture: a title, a name label, a quote or a caption. It is part of the frame you design, unlike a separate subtitle file. In vertical video, placement matters, because app buttons and the caption area can cover it.
Text overlay, caption and title card compared
People use the three terms loosely, but they do different jobs. A text overlay is the umbrella: any text drawn over footage. A caption transcribes speech and sound. A title card is a full or mostly full frame of text, usually at the start or between sections.
| Type | Job | Over the picture? | Timing |
|---|---|---|---|
| Text overlay | Label, point, name or hook | Yes, on top of footage | Set by the editor, often a few seconds |
| Caption | Show what is said and key sounds | Yes, or as a separate track | Follows the speech |
| Title card | Introduce a section or the video | Replaces or fills the frame | Short, between scenes |
| Lower third | Name and role of a speaker | Yes, near the bottom | Appears when the person first speaks |
Where text can sit on a 9:16 frame
Apps draw buttons, usernames and caption text over the video, so text near the edges can be hidden. Meta's Ads Guide suggests keeping roughly 14% of the top, 35% of the bottom and 6% of each side free of text and logos on Reels ads. If a Reels ad has disclaimers, Meta says to leave the bottom 40% clear. These are ad guides, and Meta's help page notes that screens taller than 9:16 may crop or zoom the picture.
TikTok says its safe zone depends on the video dimension and caption length, and a longer caption makes it smaller. It gives no figures in text, only downloadable guide files. For organic posts none of the platforms we read publish exact numbers, so keep key words well inside the middle. The safe zone entry has more.
Pace and length
TikTok's creative guidance for ads suggests showing 5 to 10 words per second when using captions or text overlays. The W3C accessibility guidance for captions suggests one or two lines and generally under 32 characters per line. Both are guidance, not rules, but they point the same way: short lines, left up long enough to read.
A worked example
A 30-second clip from a business podcast opens on the guest mid-sentence. At second one a three-word text overlay states the claim. At second four the lower third names the guest. Captions run word by word below the chin the whole way. Nothing sits in the bottom third, where the caption and buttons will crowd it.
Common mistakes
- Putting a text overlay where a caption sits, so the two fight for the same space.
- Treating an overlay as a substitute for captions. Accessibility standards describe captions as covering speech and important sounds, not only a headline.
- Using small type on a phone screen, or low contrast against a busy background.
- Covering a speaker's face. WCAG says captions should not obscure relevant information in the video.
Where KeyMo touches it
KeyMo's text layer is captions: 12 styles including Bold Pop, Clean and Headline, word by word, or no captions at all. Open a clip and use the chat editor to say what to change. For a hook line or a name label, see lower thirds.
Sources: Meta, Reels ads safe zone in the Instagram Ads Guide (checked 11 October 2026); Meta Business Help, Safe zone for 9:16 ads (checked 11 October 2026); TikTok Ads Help, In-feed ads specifications (checked 11 October 2026); TikTok Ads Help, Creative best practices (checked 11 October 2026); W3C WAI, Transcribing audio and video for captions (checked 11 October 2026); W3C, Web Content Accessibility Guidelines 2.2 (checked 11 October 2026).