What Is Add Line Numbers?
Add Line Numbers is a tool that prepends a sequential number to every line in your text. You control the starting number and the separator between the number and the line content. It's useful for referencing specific lines in code, documents, or lists.
The output updates in real time as you type. This tool runs entirely in your browser — no text is sent to any server.
How to Use This Tool
Enter Your Text
Type directly into the input editor, paste content with Ctrl+V, or upload/drag a .txt file.
Configure Options
Set the starting number (default 1) and separator (default ". "). Try ":", ") ", or a tab for different formats.
See Results Instantly
The numbered output appears in real time in the right panel as you type or change settings.
Copy or Download
Use Copy to copy the numbered output to clipboard, Download to save as a .txt file, or Clear to reset.
Features Explained
Custom Starting Number
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Start numbering from any positive integer. Set it to 0 to begin from zero (common in programming), or use a higher number to continue numbering from a previous section.
Custom Separator
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Choose any separator between the line number and the text content. Common options include ". " (default), ": ", ") ", a tab character, or even an empty string for no separator.
Real-Time Processing
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The output updates instantly as you type in any field — the input, separator, or start number. No need to click a button to see results. The computation is memoized for performance.
File Upload & Drag and Drop
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Upload a .txt file using the Upload button or drag and drop a text file directly onto the input area. The file contents replace the current input text.
Who Is This Tool For?
Developers
Add line numbers to code snippets for documentation, code reviews, or bug reports where you need to reference specific lines.
Writers & Editors
Number lines in manuscripts, scripts, or legal documents for easy reference during review and collaboration.
Teachers
Number lines in poems, prose passages, or exam questions so students can reference specific lines in their responses.
Lawyers
Add line numbering to legal documents, depositions, and contracts as required by court formatting standards.
Data Analysts
Number rows in data exports, CSV content, or log files for quick row identification and cross-referencing.
Students
Number lines in study materials, notes, or assignments for organized referencing and discussion.
Common Separator Formats
| Separator | Example Output | Common Use |
|---|---|---|
| ". " | 1. First line | Ordered lists, general numbering |
| ": " | 1: First line | Log files, code references |
| ") " | 1) First line | Numbered lists, outlines |
| " " | 1 First line | Tab-aligned columns, data files |
| " - " | 1 - First line | Readable numbered lists |
| "" | 1First line | Compact format, custom parsing |
Tips for Adding Line Numbers
Continue numbering from a previous section
Set "Start from" to the next number after your last section. For example, if section A ends at line 25, set Start from to 26 for section B.
Use with code snippets
Add line numbers to code before pasting into documents, emails, or presentations where syntax highlighting isn't available.
Remove numbers by using other tools
If you need to remove line numbers later, use Find and Replace with a regex like ^\d+\.\s to strip them.
Try different separators
Change the separator to match your desired format — use ") " for outlines, ": " for log-style output, or a tab for column alignment.
Upload large files
For long documents, use the Upload button or drag and drop instead of pasting. The tool handles large files efficiently in the browser.
Blank lines get numbers too
Every line gets a number, including blank lines. This preserves the correct line count and makes references accurate.
Privacy & Security
This tool runs 100% in your browser. Your text is never uploaded to any server. It is stored only in your browser's local storage so it persists when you refresh the page.
You can clear it at any time using the “Clear” button. No cookies are used, no analytics track your text content, and no third-party services have access to what you type.