Guide
Animated captions: how they work and which to use
By Rakshit · Updated
Animated captions are subtitles that move with the speech instead of sitting still: words pop in, the spoken word lights up, or a bar slides along the line. AI times them to each word. KeyMo applies them to vertical clips in 12 styles, including Karaoke, Spotlight, Slide and Punch, plus a no-captions option.
What makes a caption animated
A normal caption is a block of text that appears for a few seconds. An animated caption is timed to individual words. The AI part is the timing: speech recognition marks when each word starts, and the caption reacts at that moment. What the caption does at that moment is the style.
Four basic moves show up in the styles below.
- Highlight: the whole line stays on screen and the spoken word changes colour or size.
- Pop-in: each word, or a small group, appears with a quick scale-up as it is said.
- Slide: a bar or marker travels along the line and sits under the spoken word.
- Fade or cut: words fade in one by one, or a whole group appears at once and is replaced by the next.
The 12 KeyMo styles sorted by motion
Most KeyMo styles react word by word, while Classic, Duo and Headline show a whole group at once. This table groups the styles by how they animate. Look descriptions come from the style definitions in the KeyMo caption overlay code.
| Motion | Styles | What you see |
|---|---|---|
| Highlight | Spotlight, Karaoke, Reader | Spotlight greys the line and lights the spoken word in mint. Karaoke lights the active word in green and enlarges it. Reader puts the sentence on a light rounded box and darkens words as they are said. |
| Pop-in | Punch, Pulse, Bold Pop | Words scale in with a small overshoot. Punch is heavy and italic with a slight tilt, Pulse is magenta, and Bold Pop has a thick black outline. |
| Slide | Slide | A purple bar slides under the active word, which grows slightly. |
| Keyword colour | Pro Glow, Duo, Headline | A key word or second line takes an accent: a glow for Pro Glow, green for Duo, yellow for Headline. |
| Fade or cut | Clean, Classic | Clean fades words in one by one in sentence case. Classic shows a whole group at once in big condensed capitals, then cuts to the next. |
There is also a no-captions option, which exports the clip without text. For a closer look at when each style suits a clip, see the caption styles gallery and the word-by-word captions guide.
Keeping animated captions readable
Motion draws the eye, and that is the point, but it can also make text harder to read. A few checks help whatever tool you use.
- Words per line. The W3C accessibility pages say captions are one or two lines and that it is generally best to keep them under 32 characters per line. That is guidance, not a rule.
- Pace. TikTok's ad best-practice page recommends 5 to 10 words per second when you use captions or text overlays. It is advice for ads, so treat it as a reference point for pace and not a rule for every clip.
- Capitals. The W3C advises against all capitals for emphasis, except to indicate yelling. Several animated styles are uppercase by design, so use them for energetic speech, not for a calm interview.
- Cover. WCAG notes that captions should not obscure relevant information in the video. KeyMo is set up to place its captions at about chest height, below the speaker's mouth.
- Accuracy. Animation makes a wrong word more visible, not less. Read the captions before you post.
Making them with KeyMo
KeyMo is built for clips, so the animated captions come as part of the render and not as a separate editing step. Upload a video of 5 minutes to 3 hours, or paste a YouTube link on a paid plan. KeyMo picks up to 15 moments, each scored out of 10, and renders those scoring 7 or higher in vertical 9:16 at 1080x1920. Choose a style, and every clip gets it. To change it for one clip, open the clip in the editor.
It is not a stand-alone animated subtitle maker for videos you do not want clipped, and there is no free plan or trial, so animated captions free and free animated subtitles are not what KeyMo offers. Starter is $12 a month for 300 source minutes. There is no watermark on any plan.
Animated captions suit Reels and Shorts equally: the clip is the same vertical file on both. See auto captions for Reels and auto captions for YouTube Shorts for placement on each.
Sources: W3C WAI: Transcribing Audio to Text (checked 11 October 2026); W3C: Web Content Accessibility Guidelines (WCAG) 2.2 (checked 11 October 2026); TikTok Ads Help: Creative best practices (checked 11 October 2026); W3C WAI: Captions/Subtitles (checked 11 October 2026).