A padded review checklist
Start 10, increment 10, and digit width 3 generate 010, 020, 030. With the default separator, “Inspect source” becomes “010. Inspect source”.
0 numbered lines of 0. No numbers generated.
Maximum 100,000 UTF-16 code units and 10,000 lines. Start: 0–1,000,000; increment: 1–100,000; digit width: 1–10. Existing numbers are preserved as input text. CRLF and CR become LF. Processing stays in this browser; text is not submitted to a server.
Text is processed locally in your browser. No tool input is sent to a remote processing service.
How to use the Line Numberer
- 01
Paste the lines you want to label.
- 02
Set a whole-number start and positive increment. Choose the minimum digit width for zero padding.
- 03
Enter an optional prefix and the text that separates each number from its line.
- 04
Choose whether to skip blank lines, inspect the last generated number, and copy or download the output.
Examples
Match existing reference numbers
If an excerpt begins at source line 240, set Start at to 240 and leave increment at 1. The pasted lines receive labels 240, 241, 242, and so on.
Preserve paragraph spacing
With blank-line skipping enabled, alpha, an empty line, and beta become numbered alpha, an unchanged empty line, and the next consecutive numbered beta. The blank line consumes no number.
Labels become part of the exported text
The generated prefix, number, and separator are inserted at the beginning of each numbered line. This differs from a code editor’s line-number gutter, which usually is not copied with the document. Use the output for review references, printed instructions, or an annotated excerpt. Numbering changes the contents of the text, so do not paste the result into executable source code or structured data unless that format permits the added labels.
Control the sequence and its appearance
The start value can be zero through 1,000,000, and the increment can be 1 through 100,000. Digit width is a minimum from one through ten; numbers are padded with leading zeros but never truncated. A prefix appears before the padded number and a separator after it. For example, prefix L, width four, and separator “: ” produce L0001: before the first line when starting at one. Prefixes and separators each allow at most 20 UTF-16 code units and no newlines.
How blank lines affect numbering
By default, every line receives a number, including empty lines and a final empty line caused by a trailing newline. Enable blank-line skipping to preserve whitespace-only lines unchanged and advance the sequence only for substantive lines. This is useful for paragraph-spaced notes. It is unsuitable when labels must match physical file line positions, because the skipped blank rows break that correspondence.
Numbering is additive
Existing numbers are treated as ordinary line content. If the input already says “1. First task”, numbering adds another label rather than trying to guess which prefix to remove. Work from an unnumbered source when possible. Up to 100,000 UTF-16 code units and 10,000 input lines are accepted. CRLF and CR line endings are normalized to LF, while spaces and tabs inside the original lines remain untouched.
What to know
- Maximum 100,000 UTF-16 code units and 10,000 input lines.
- Adds plain-text labels only; existing numbering is not removed and formatting metadata is not retained.
Common questions
Can the sequence count downward?
No. This tool accepts a nonnegative start and a positive increment. It is designed for forward reference labels.
Does zero padding limit the largest number?
No. A width of two gives 01 through 99, then 100. The number is never shortened to fit the width.
Can I remove old line numbers automatically?
No. Existing prefixes are preserved. Removing them requires a deliberate find-and-replace rule matched to your input format.