About the Add Line Numbers
Add numbers writes a number and a separator before each line. Start is the first number and Step the difference between two lines, so start 10 and step 10 gives 10, 20, 30, and a negative step counts down. The separator can be 1. , 1: , 1) , a tab, 1 | , a single space or any text of your own. Padding makes all numbers as wide as the largest one, with spaces (right-aligned, like cat -n) or with zeros (001), which keeps the text aligned and makes the lines sort correctly as text.
Blank lines can be numbered like the others, left without a number (the count continues on the next line with text, like nl does by default) or removed. Lines may end in LF, CRLF or CR, and a final line break does not produce an extra numbered line.
Remove numbers detects the format used by most lines: 1. , 1: , 1) , [1] , (1) , 1 | , 1 - , a tab or a space after the number, with or without padding. Only the lines in that format are changed, so a line that begins with 3.14 or with a date such as 2026-03-15 is not damaged, and at most one space after the separator is removed so that the indentation of code survives. Swap moves the result to the input and switches the mode.
How to use it
- Paste the text or open a file.
- Choose Add numbers or Remove numbers.
- Set the start, step, separator and padding, and what happens to blank lines.
- Copy the result or download it.