Guide · ~6 min read
Subtitle line length for TikTok, Reels, and Shorts
Horizontal subtitle rules break on 9:16. This guide explains character limits, how to scan an entire SRT, and when to split lines without breaking grammar.
Why vertical video needs shorter lines
Phone screens are narrow. A line that worked on 16:9 may wrap to three rows on Reels, blocking product shots and faces. Editors often cap characters per line instead of guessing after export.
Starting thresholds (English)
| Platform style | Chars / line (starting point) |
|---|---|
| TikTok talking head | 28–36 |
| Reels / Shorts punchy captions | 24–32 |
| Educational vertical | 32–42 |
Run your file through the caption line length checker with your chosen max; fix outliers first (often auto-caption merges).
How to split lines without ruining timing
- Split at punctuation or natural phrase breaks—not mid-idiom.
- Keep both lines under the cap; balance line 1 vs line 2 length.
- Avoid splitting a single cue into two timecodes unless readability demands it.
- Re-export SRT and re-run the checker.
Pair with timing fixes
Short-form often needs both readable line breaks and sync fixes. Use SRT time shift after re-timing dub audio, then line length check before final render. For VO planning see read time estimator.
How to use
- Paste or upload your SRT in the browser checker.
- Set max characters per line (try 32–40 for Reels).
- Edit flagged cues in your editor, re-check until clean.
Frequently asked questions
- What is a safe line length for TikTok or Reels captions?
- Many editors aim for roughly 28–42 Latin characters per line on 9:16, depending on font size. Shorter lines read faster on mobile.
- Why do long subtitle lines fail on vertical video?
- Narrow frame width wraps text into tall blocks that cover faces and safe zones. Two short lines usually beat one long line.
- Does character count include spaces?
- Yes for readability checks. CJK scripts may use fewer characters with similar visual width—adjust thresholds per language.
- Can I check an entire SRT file at once?
- Paste or upload the full SRT in the line length tool; it reports the longest lines and per-cue counts.
- Is this a replacement for platform auto-captions?
- No. It audits files you already authored or exported, before burn-in or upload.