Code 39 Barcode Generator
Updated Free mock REST & WebSocket APIs
Generate Code 39 — also called Code 3 of 9 — barcodes for asset tags, ID badges and systems that require it. Lowercase is converted automatically and you can add the optional mod 43 check character.
Encoded ABC-1234 · 358×122px
Size, text and colors
🔒 Encoded and drawn in your browser — no uploads, no watermark, free for commercial use.
How to create a Code 39 barcode
- Enter uppercase letters, digits, spaces or - . $ / + %.
- Tick “Mod 43 check character” if your scanner or spec requires it.
- Download SVG or PNG. The asterisks shown are the start/stop characters and are added automatically.
How Code 39 works
Each character is 9 elements — 5 bars and 4 spaces — of which exactly 3 are wide, hence “3 of 9”. Characters are separated by a narrow gap and the whole code is wrapped in * start/stop characters. This tool uses a 3:1 wide-to-narrow ratio, inside the 2:1–3:1 range the standard allows.
Mod 43 check character
Give each character its value (0–9 = 0–9, A–Z = 10–35, then - = 36, . = 37, space = 38, $ = 39, / = 40, + = 41, % = 42), add them, and take the remainder after dividing by 43. For CODE39: 12 + 24 + 13 + 14 + 3 + 9 = 75; 75 mod 43 = 32, which is W.
Related tools
Embed this tool on your site
Browse all embeddable tools →Free for blogs, HR, payroll and contractor sites: copy one snippet — the widget sizes itself and matches your colors.
Get the embed code
Frequently asked questions
Why does my scanner show the asterisks?
It shouldn't — they're start/stop characters. Some scanners need a setting changed to strip them, or to validate and drop the mod 43 check character.
Can Code 39 encode lowercase?
Standard Code 39 can't. “Full ASCII” Code 39 represents lowercase with two-character pairs, but the scanner must be set to decode it, so this tool converts to uppercase instead. For lowercase, use Code 128.
Is anything sent to a server?
No. Everything is generated by JavaScript in your browser, so nothing you type or generate is uploaded, logged or stored. It keeps working offline once the page has loaded.
Your business here? Sponsor this tool from $16/week. See placements