Line Length Checker

How to use

1. 1Paste your text or code into the input box, or press Load sample to try a worked example with a few over-length lines.
2. 2Choose how to measure: Display width (tab-aware monospace columns) or Characters (Unicode code points).
3. 3Set the maximum line length directly or pick a preset such as 79 (PEP 8), 80 (Prettier), 100, or 120, and choose the tab width for display-width mode.
4. 4Read the summary for the longest line, the average width, and how many lines are over the limit.
5. 5Scan the ruler view of the longest line to see where it overflows, and use the table to review every line that is too long.
6. 6Click Copy line numbers to grab the offending lines, or Copy report for the full plain-text breakdown.

About this tool

Line Length Checker measures how long every line in a block of text or code is and tells you which lines run past a width you set. A word counter gives you a single total; this tool works line by line so you can answer the questions a style guide and a code review actually care about: which line is the longest, exactly how long is it, how many lines break the column limit, and by how much. It reports two different lengths because they are genuinely different numbers. Characters counts Unicode code points, so an emoji or other astral-plane character counts as one, not the two UTF-16 units that a naive length would give. Display width counts monospace columns the way an editor ruler or a terminal does: a tab is not one column, it advances to the next tab stop (the next multiple of the tab width you choose), East Asian and fullwidth characters and most emoji take two columns each, and combining accent marks and zero-width characters take none. Display width is the default the limit is checked against because that is what a max line length rule really limits. You set the limit directly or with one click from presets that match the conventions people use: 72 columns for the body of a Git commit message, 79 for Python under PEP 8, 80 for Prettier and many C and Go style guides, and 100 or 120 for teams that prefer wider lines. You also pick the tab width (2, 4, or 8) used when expanding tabs for the display-width measure. The summary shows the total line count, the longest and shortest lines with their line numbers, the average width, the number of lines over the limit, and how many lines have trailing whitespace. A ruler view draws the longest line against a column scale with the over-limit portion highlighted in red and tabs and spaces made visible, so you can see exactly where it overflows. A sortable, scrollable table lists every offending line with its measured width, how far over it is, and a preview of the text, and you can copy just the line numbers (handy for jumping to them in your editor) or copy a full plain-text report. Typical uses include checking code against a linter's max-line-length rule before committing, finding the one stray line that fails CI, keeping documentation and comments inside a wrapping width, sizing translated UI strings and subtitle lines, and reviewing pasted text for lines that are too wide to read comfortably. Everything runs locally in your browser as you type, so the text or code you paste is never uploaded, logged, or stored.

Free to use. Works in your browser. No signup, no login.