CPL Line-Length Checker

Why line-length limits exist

A characters-per-line (CPL) limit isn't an arbitrary style rule — it comes from three real constraints stacked on top of each other. First, the player safe area: broadcast and streaming players reserve a margin around the edge of the frame so text never clips on a consumer TV's overscan, which caps how many characters physically fit before a line wraps or spills off-screen. Second, font metrics: caption fonts are rendered proportionally wide (readable at a distance, often at a fixed size regardless of video resolution), so a limit tuned for that font's average glyph width is what keeps a line inside the safe area at every resolution a viewer might watch on. Third, reading ergonomics: even a line that technically fits the screen can be too dense to read in the few seconds it's on screen — long unbroken lines force a viewer's eye to sweep further per line, which fights against the reading-speed budget a caption already has to hit. A CPL limit is the byproduct of all three, tuned per platform to the font, screen and audience it's designed for.

The pinned preset table

Sources, checked on 3 October 2026. Netflix's per-language Timed Text Style Guides (hub: Timed Text Style Guides) give 42 characters per line under "Character Limitation" in English (USA) (change log's latest entry 2025-12-19), Spanish, French (France), German, Italian, Portuguese (Brazil) and Russian; 16 in Korean, Chinese (Simplified) and Chinese (Traditional); and 13 full-width characters for horizontal subtitles (11 for vertical) in Japanese. The 37 comes from section 3.1 of the BBC Subtitle Guidelines. The Netflix figures are the interlingual subtitle limits (the Japanese SDH section allows 16 horizontal). Netflix's QC help page adds that its automated check enforces looser limits outside Netflix Originals (Korean and Chinese 23) and the 16 shown here for Originals. Both organizations revise their guides over time, so treat these as the current numbers, not a permanent standard, and confirm against the live guide for a paying delivery.

Where the 42 and the 37 come from

Only one of the two origins is documented in a source we could check. The BBC Subtitle Guidelines say that in Teletext, which is used to display subtitles on some broadcast platforms, line length is limited to 37 fixed-width characters, since at least 3 of the 40 available bytes are used for control codes (section 3.1, checked on 3 October 2026). We have not found a primary source for how Netflix arrived at 42 for Latin-script languages, so this page does not offer an origin story for it: treat 42 as Netflix's stated limit, not as a derivation.

How counting works

This tool counts Unicode code points — every character in the pasted line, including spaces and punctuation, counts toward the limit. A 42-character Netflix line really means 42 total characters, not 42 words or 42 "visible" glyphs. For the CJK presets, each CJK character counts as 1, because CJK scripts are conventionally measured in full-width character units rather than Latin-style letter counts — a 13-character Japanese line is 13 kanji/kana, not 13 of anything smaller. The surprise comes when a line mixes full-width CJK characters with half-width Latin punctuation or Romaji: a code-point count treats every character as one unit regardless of its rendered width, so a line that looks short on screen (because CJK glyphs are visually wider) can still hit the code-point limit faster than the eye expects, and a line padded with half-width characters can look longer than its count suggests. Always check the rendered width in your caption tool alongside a character count for mixed-script lines. Netflix's own count differs in one respect (checked on 3 October 2026): its Korean guide counts Latin characters, spaces and punctuation as 0.5 character, and its Japanese guide counts half-width characters as 0.5 and full-width characters as 1, where this tool counts every character as 1.

One line vs two, and where to break well

Most specs cap a subtitle event at two lines. When a line needs to break, break at a natural syntactic boundary — after a clause, a conjunction, or a complete phrase — never in the middle of a phrase that has to be read as one unit. Don't orphan a short article or preposition ("the", "a", "of", "to") alone on a line; it reads as a stray fragment and forces the eye back up. A well-broken two-line caption balances line lengths roughly evenly rather than cramming one line and leaving the other nearly empty — an unbalanced break is harder to read even when both lines are individually within limit.

Fixing an over-limit line

Three fixes, in order of preference: rephrase the line to say the same thing more concisely (cut filler words, tighten phrasing) without losing meaning; rebalance the two lines of the event so the break point sits earlier or later at a cleaner syntax boundary, redistributing characters without changing the words; or, if the dialogue genuinely needs more room than two lines can hold, split the event into two consecutive cues with their own timing. Never solve an over-limit line purely by shrinking the caption font or letting it overflow the safe area — that reintroduces the exact problem the limit exists to prevent.

1. Paste your subtitle lines into the box, one line per row.

2. Pick a preset - Netflix 42 for Latin and Cyrillic, BBC 37, Netflix CJK at 13 or 16, or a custom house limit.

3. Scan the ruler for bars past the limit, then check how fast those lines read with the Netflix CPS Reading-Speed Checker.