Line Numberer

About this tool

Adding line numbers to text is a small task that comes up more often than you would expect: sharing a code snippet where you need to reference specific lines in a discussion, preparing a document for review where annotators will cite line numbers, creating a numbered script or screenplay, or generating a quiz answer key with numbered items. Line Numberer adds line numbers to any block of text with control over the starting number, the separator text placed after each number (up to 16 characters, '. ' by default), zero-padding, and whether empty lines are numbered. Auto padding, on by default, pads every number to the width of the largest one; turn it off to set a fixed Padding width from 1 to 12. Numbers can start at any value, allowing continuation from a previously numbered section. The output updates as you type and can be copied with one click.

Why use it

• Custom Starting Number: Start at any line number to continue numbering from a previous section or match an existing document's line references.

• Free-Form Separator: Type any separator up to 16 characters — period, colon, pipe or a pasted tab — to match your document or code style.

• Zero-Padding for Alignment: Pad numbers with leading zeros so columns align correctly in monospace code editors and terminals.

• Empty Line Control: Decide whether blank lines get a number or are skipped — important for prose documents where blanks are paragraph breaks.

• Instant Preview: Output updates in real time as you adjust settings — no need to re-paste your text for each configuration change.

• Works for Code, Scripts & Documents: Useful equally for code snippets shared in forums, numbered draft documents, quiz answer keys, and stage scripts.

How to use

1. Paste your text into the Input text box.
2. Set the Start number (default is 1).
3. Type the Separator to place after each number, such as '. ', ': ' or a pasted tab.
4. Keep Auto padding on to pad numbers to the same width, or turn it off and set a Padding width from 1 to 12.
5. Tick Skip empty lines if blank lines should stay unnumbered.
6. The numbered output updates as you type; click Copy output to copy it.

When it helps

• When sharing a code snippet in a forum or pull request comment where lines need to be referable by number.
• When preparing a document for peer review or legal annotation where reviewers cite specific lines.
• When creating a numbered list of instructions or steps where sequential numbering is required.
• When generating a line-numbered transcript or script for production notes.
• When debugging output that needs line context to cross-reference with a source file.
• When formatting a numbered quiz, test, or answer sheet where each item must have a sequential number.

Examples

function hello() {
  return 'world';
}

1: function hello() {
2:   return 'world';
3: }

Line one
Line two
Line three

001: Line one
002: Line two
003: Line three

Apple
Banana
Cherry

10	Apple
11	Banana
12	Cherry

Tips

• Paste a tab character into the Separator field when you plan to paste the numbered output into a spreadsheet — each number will land in column A and the line content in column B.
• Set padding width to match the expected total line count: 3 digits for documents under 1,000 lines, 4 for larger ones.
• Skip empty lines for prose documents so paragraph breaks do not consume sequence numbers.
• Number empty lines for code snippets so the output matches what developers see in their editor's gutter.
• Start at a number other than 1 when the snippet is extracted from the middle of a larger file and you want references to match the original file's line numbers.

Frequently Asked Questions

Glossary

Line number

A sequential number prepended to each line of text, used to allow precise reference to specific lines in a document or code listing.

Zero-padding

Adding leading zeros to numbers so all numbers have the same digit width, enabling proper column alignment in monospace fonts.

Separator

The character(s) placed between the line number and the line content, such as a colon, tab, or space.

Gutter

The narrow column to the left of code in an editor that displays line numbers, breakpoints, and other indicators.

Monospace font

A font where every character occupies the same horizontal width, making character-based alignment and column formatting reliable.

Continuation numbering

Starting a numbered section from a value greater than 1 to continue the line count from a previous section of a document.