BASIC Line Renumbering Tool

by E. Wenners, 2026

This tool renumbers classic line‑based BASIC programs — including Commodore 64 BASIC and many other dialects that use GOTO, GOSUB, and numeric line references.

It takes your BASIC listing, renumbers every line, and automatically updates all jump targets so the program remains functional after cleanup.

Usage

• Paste your source code into the textarea
• Set the starting line number (default: 10)
• Set the increment (default: 10)
• Choose whether to insert a space between the line number and the code (default: on)
• Click Renumber

What the tool updates

The renumbering engine automatically adjusts:

• GOTO <line>
• GOSUB <line>
• THEN <line>
• ON X GOTO <line1>,<line2>,<line3>...
• ON X GOSUB <line1>,<line2>,<line3>...
• All jump targets outside of quoted strings

It also:

• Replaces empty lines with REM * to preserve numbering
• Leaves all text inside strings untouched

Notes

This tool is written in PHP and works entirely server‑side — no dependencies, no installation, just paste and renumber.

Disclaimer

This tool is provided as‑is without any warranties. Always keep a backup of your original code before using the renumbering tool.

Try it online

Test it here: https://chaozz.nl/github/renumber.php