Instagram Reels with text over most of the frame: cap caption size

Instagram's help page says you may see less often Reels whose image is mostly covered by text. It gives no percentage, so there is no number to hit. With Sume's video captions you can still bound the text area, because the design object has three fields that set it: typography.font_size_ratio (0.01 to 0.4), typography.safe_width_ratio (0.3 to 1) and phrasing.max_words (1 to 12). Instagram's help page renders in the browser and could not be fetched as plain text, so the wording here comes from the search excerpt of that page on 2026-10-08. Open the page to confirm before you rely on it.

How the three fields shape the text area

font_size_ratio is the type size as a fraction of a 1080-wide frame, before the in-browser fit shrinks a long line. safe_width_ratio is the fraction of the frame width a caption line may occupy. max_words and max_chars (4 to 60) set how much appears at once. Together they bound the bounding box of what is on screen at any moment. The arithmetic is below for a 1080x1920 Reel; it measures box area, not ink, and is not an Instagram test.

Request

The design object merges over the style you pick, and each field is optional. A number outside its documented range gives a 400 up front, so you do not pay for a wrong render. punch and tiktok-green do not accept design; use slam for Latin text or black-outline. If a style is not sent, Latin speech resolves to slam.

{
  "video_url": "https://media.sume.com/artifacts/artf_demo/talking-head.mp4",
  "style": "slam",
  "design": {
    "typography": { "font_size_ratio": 0.07, "safe_width_ratio": 0.8 },
    "phrasing": { "max_words": 3 }
  }
}

Reading the table

A two-line caption at 0.07 uses about 7.5% of the frame by box area, and the page's wording, "majority of the image covered by text", is far from that. The third row at 23% is still under a quarter. The risk is rarely the burned captions; it is the sum of captions, stickers, title cards and on-screen product text added in other tools. Count all of them. The video captions price is $0.20 per accepted job for clips up to 60 seconds.

Where to place the line

placement.anchor_ratio (0.05 to 0.95) is the center of the line as a fraction of frame height. Keep it away from the bottom area where the Reels interface sits. Reels ad safe zone in pixels works that out for a 1440x2560 frame.

Speech-to-captions needs audible speech; a silent clip fails with caption_no_speech. For a silent clip, send authored cues with text, start and end.