YouTube .vtt: positioning yes, styling only b/i/u. Sume design options
YouTube's .vtt support allows positioning but limits styling to bold, italic and underline. Sume burns richer styling; see which route fits your look.
What YouTube lists
YouTube's subtitle file type page says .vtt supports positioning, with styling limited to bold, italic and underline. By comparison it describes .srt and .sbv as basic with no style markup, and .ttml as supporting styling and positioning.
The WebVTT specification defines cue settings including line, position and align, which is where positioning comes from.
What this means for brand look
If your brand uses a coloured active word, a stroke, or a pill background, a .vtt file on YouTube will not carry it. You get white-or-whatever-the-viewer-sets text, in the viewer's settings, at the position you choose.
Sume's burn-in is the route for a designed look. The design object overrides colours, typography, placement, phrasing and motion for one request.
| Control | YouTube .vtt | Sume burned-in `design` |
|---|---|---|
| Text colour | Viewer's player settings | colors.base, colors.active |
| Outline | Not listed | colors.stroke, typography.stroke_width_px |
| Bold / italic / underline | Yes | Weights via typography.base_weight |
| Vertical position | Cue settings | placement.anchor_ratio |
| Background card | Not listed | colors.card or null for none |
Support caveats
Do not assume every design field works on every style: design is not supported on punch or tiktok-green. Colours must be hex, rgb(), rgba() or transparent; anything else is rejected with a 400 rather than silently drawn.
Out-of-range numbers are rejected too, so a bad look fails at request time instead of billing for a wrong render.
A recommended split
- Burn your branded look into the video you publish.
- Upload a plain .vtt as a track for accessibility, with default viewer styling.
- Do not rely on the .vtt for brand colours.
- Test both on a phone screen before you publish.
Safe zones on a phone
Positioning is only useful if the text clears the platform's own interface. Sume's placement.anchor_ratio is the line centre as a fraction of frame height, and landscape_anchor_ratio does the same for landscape. Preview on a real phone before you commit to a ratio.
If the platform draws buttons and titles over the lower third, place captions higher than you would for a plain video file.
Takeaway
A YouTube .vtt can position text and apply bold, italic or underline. Anything branded comes from burning it in with Sume's design overrides.
Sources
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Written by Sume