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: the Netflix Timed Text Style Guide hub (per-language guides, each maintained separately) and the BBC Subtitle Guidelines. Both organizations revise per-language limits over time, so treat these as the current de-facto numbers, not a permanent standard — always confirm against the live guide for a paying delivery.

Why 42 for Latin scripts became the standard

42 characters is roughly what a 1990s teletext line could hold and what a 32-inch CRT's safe area allowed at a legible caption font size — Latin-script broadcast captioning converged on values in the high-30s to low-40s decades before streaming existed, and Netflix's style guide inherited and formalized that number when it wrote the modern timed-text spec. It has stuck because it works across the widest range of displays streaming actually ships to, from phones to living-room TVs.

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.

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.