What Is the Add Line Numbers Tool?
The Add Line Numbers tool prefixes each line of your text with a sequential number. Six format styles let you choose exactly how numbers appear — plain, zero-padded, with a dot, colon, brackets, or tab separator. You can start from any number, set a custom step/increment, and optionally skip empty lines. All processing is instant and runs entirely in your browser.
How to Use the Add Line Numbers Tool
- Paste your text — code, a list, or any multi-line content — into the input box.
- Choose a format — Dot suffix (
1. line) is the most common; Zero-padded is great for large files. - Set the start number and step — defaults to start at 1, increment by 1.
- Toggle Skip empty lines if you want blank lines to pass through unnumbered.
- Copy or Download the numbered output.
Where Can You Use Add Line Numbers?
Code Review
Add line numbers to a code snippet before pasting into a document or email so reviewers can reference specific lines by number.
Numbered Lists
Convert a flat bullet list into a properly numbered list for reports, essays, or documentation without manually typing each number.
Data Indexing
Add sequential row numbers to a CSV or TSV export for tracking and reference when importing data into a spreadsheet.
Test Sequences
Number test steps, interview questions, or checklist items starting from a custom number to continue an existing sequence.
Format Styles Available
- Plain —
1 Line text— Simple space-separated number. Works in any context. - Zero-padded —
001 Line text— Pads numbers with leading zeros so columns align. Best for files with 100+ lines. - Dot suffix —
1. Line text— Standard numbered list format used in documents and reports. - Colon suffix —
1: Line text— Common in log files and script outputs. - Bracket —
[1] Line text— Reference-style numbering used in academic papers and changelogs. - Tab separator —
1⇥Line text— Tab-delimited, suitable for importing into spreadsheets as a two-column layout.
Best Practices and Limitations
Use Zero-padded format when your file has more than 9 lines and you want consistent column alignment in a monospace font. Use a step of 5 or 10 when you plan to insert additional lines later — leaving gaps between numbers saves you from renumbering the entire file.
Limitations:The tool numbers lines as-is — it does not understand code structure, so a multi-line string or comment will have each physical line numbered individually. If you're numbering code for a diff or code review tool, verify that the line numbers match what your editor or IDE reports (editors sometimes differ on blank-line handling or trailing newlines).
Share This Tool
Share this free online line numbering tool with your team or fellow developers!