Code 128 Barcode Generator
Updated Free mock REST & WebSocket APIs
Encode letters, digits and symbols as a compact Code 128 barcode. The generator switches between code sets A, B and C automatically for the shortest symbol and adds the check character for you.
Encoded MOCKFOX-2026 · Code sets B + C · check value 84 · 14 symbols · 352×122px
Size, text and colors
🔒 Encoded and drawn in your browser — no uploads, no watermark, free for commercial use.
How to create a Code 128 barcode
- Type or paste your data — SKUs, serial numbers, tracking numbers, URLs (ASCII only).
- Check the summary line to see which code sets were used and the check value.
- Download SVG or PNG and place it on your label with its quiet zone intact.
Code sets A, B and C
| Set | Characters | Start value |
|---|---|---|
| A | Uppercase, digits, punctuation and control characters (ASCII 0–95) | 103 |
| B | Uppercase, lowercase, digits and punctuation (ASCII 32–127) | 104 |
| C | Pairs of digits 00–99 — two digits per symbol | 105 |
Code C halves the width of long numbers, so the encoder starts in C for 4+ leading digits and switches into C for runs of 4+ digits at the end or 6+ in the middle. Each symbol is 11 modules wide (three bars and three spaces), and the stop pattern is 13.
The check character
The checksum is the start value plus each symbol value multiplied by its position, modulo 103. For 1234 in Code C: 105 + 1×12 + 2×34 = 185, and 185 mod 103 = 82. Scanners verify it and don't show it, so it isn't printed in the human-readable text.
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Frequently asked questions
Code 128 vs. Code 39 — which is better?
Code 128 is denser (often half the width), supports lowercase and all ASCII, and has a mandatory check character. Use Code 39 only when a system requires it.
Can it encode GS1-128 (UCC/EAN-128)?
GS1-128 needs a special FNC1 character after the start code, which this tool doesn't add yet. Plain Code 128 works for most internal and shipping labels.
Is there a length limit?
The standard has none, but long codes get wide and harder to scan. This tool caps data at 80 characters; most scanners comfortably read 20–40.
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.
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