Line Numbering Tool

What Is the Line Numbering Tool?

This tool prefixes every line of text or code with its line number -- right-aligned and padded to a consistent width -- the format code snippets, log excerpts, or line-referenced documentation commonly use.

How to Use This Tool

Paste text or code, set a starting number and separator (like ": " or ". "). The numbered result appears instantly.

How the Numbering Works

Worked Example

Practical Uses

• Adding line numbers to a code snippet for documentation or a tutorial
• Referencing specific lines when discussing a log excerpt or data file
• Preparing numbered text for easier verbal or written line-by-line reference

For adding line numbers as part of code display formatting, pair with the HTML Beautifier or CSS Beautifier when documenting formatted code.

How the Numbers Are Built

The tool splits your text into lines at each line break, then adds the starting number plus the line position to each one. The width of the number column is set by the largest number that will appear, and shorter numbers are padded on the left with spaces so the separators line up. The separator you type is inserted exactly as written, including any spaces, and then your line follows. The tool starts with the starting number at 1 and a separator of a colon followed by a space.

Worked Example With a Custom Start

Imagine you are quoting lines from the middle of a configuration file and want them to match the original line numbers. You paste three lines and set Start At to 98. The largest number is 100, which has three digits, so every number is padded to width 3. The result reads " 98: first line", " 99: second line" and "100: third line", with the first two numbers indented by one space so the colons line up. Without the width padding, the change from two digits to three would have shifted the text and made the block harder to read.

Choosing a Separator

• A colon and space suits quoted log lines and command output.
• A period and space suits step-by-step instructions where each line is a step.
• A space, a vertical bar and a space suits code listings, where the bar visually separates the gutter from the code.
• A tab character gives clean columns when pasted into a spreadsheet, though you may need to paste it into the field from another source.

Things to Watch For

Every line receives a number, including blank ones, so an empty line still gets its own row. If your text ends with a trailing line break, the final empty line is numbered too. If you do not want that, remove the trailing break before numbering. If the Start At field is empty or contains something that is not a number, the tool falls back to 1. A start value of 0 is also treated as 1 because zero counts as an unset value, so if you need numbering that begins at zero, number from 1 and adjust the labels afterward.

Negative starting numbers are accepted by the number field, and the minus sign counts toward the column width when it appears. Because the numbers are padded with spaces, paste the result into a monospaced font, such as a code block, to keep the alignment visible. In proportional fonts, the columns may look slightly uneven even though the underlying text is correct.

When Numbering Helps

Numbered lines make it easier to discuss a code snippet in a review, reference a specific entry in a log, or ask someone to change a line in a pasted list. Remove the numbers again before feeding the text back into a program, since the numbers are now part of each line.

Frequently Asked Questions