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Number Every Line of Your Text Add sequential line numbers to each line of text.

Add Line Numbers illustration
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Add Line Numbers

Add sequential line numbers to each line of text.

1

Paste Text

Enter the text you want to add line numbers to.

2

View Numbered Text

See each line prefixed with its sequential line number.

3

Copy Result

Copy the numbered text for documentation or sharing.

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What Is Add Line Numbers?

Add Line Numbers is a text processing tool that adds sequential line numbers to each line of text, allowing users to easily reference specific lines in documents, code snippets, or data files. Developers and technical writers use it to number lines of text in code reviews, documentation, and error reporting, where referencing specific positions in a text is crucial. One specific problem it solves is the tedious manual process of numbering each line of code or text, which can lead to errors and inconsistencies.

The tool is different from other line numbering tools because it provides options for customization, such as setting the starting number, choosing a separator between the number and the line content, and padding with zeros. For instance, users can choose to start numbering from 1 or any other number, and select a separator like a period or a space. It also allows users to prepend line numbers to text online, making it a convenient line numbering tool for collaborative work.

It enables precise control over the output format, allowing users to add line numbers to text in a way that suits their needs. By using this tool, users can efficiently number each line of text and produce consistently formatted output, which is particularly useful when working with large codebases or documents. The customizable features make it an ideal solution for tasks that require precise line numbering, such as adding line numbers to code snippets or data files for reference or analysis.

Why Use Add Line Numbers?

  • Add line numbers in one click
  • Consistent padding for aligned output
  • Essential for code snippets and documentation
  • Makes line referencing easy in reviews
  • Handles any text content

Common Use Cases

Code Documentation

Number code lines for reference in documentation, tutorials, and code reviews.

Error Reporting

Add line numbers to logs or output for easier error location reporting.

Legal Documents

Numbered lines in legal documents allow precise cross-referencing.

Teaching Material

Numbered example text helps students follow classroom discussion and annotation.

Technical Guide

Line numbering splits input on newlines, computes the number of digits needed for the highest line number (Math.ceil(Math.log10(totalLines + 1))), then pads each number with leading spaces for right-alignment. The separator (default ": ") is placed between the number and the line content. Numbering starts at 1 by convention (matching most text editors and IDEs). The padding ensures consistent alignment regardless of line count — a 100-line text uses 3-digit padding (e.g., " 1: ", " 10: ", "100: ").

Tips & Best Practices

  • 1
    Use padded numbers for aligned output in monospaced fonts
  • 2
    Line numbers make code snippets easier to discuss in reviews
  • 3
    Remove line numbers with the Remove Line Numbers tool when done
  • 4
    Numbered text is useful for creating study guides and annotated documents
  • 5
    Most IDEs show line numbers natively — use this for sharing plain text

Related Tools

Frequently Asked Questions

Q What number does line numbering start from?
Line numbering starts at 1, matching the convention used by text editors and IDEs.
Q Are the line numbers padded for alignment?
Yes, numbers are right-aligned with consistent padding so all lines align properly.
Q Can I change the line number separator?
Yes, the separator is customizable. The default is ": " (colon followed by space).
Q Does the tool number blank lines too?
Yes, all lines including blank lines receive a number.
Q How do I remove line numbers later?
Use the Remove Line Numbers tool to strip the numbers and restore the original text.

About This Tool

Add Line Numbers is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.