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Number and Letter Generator
Generates cryptographically secure random alphanumeric strings with your choice of length and character set.
Last updated: June 2026 · Free · No sign-up required
Results
Enter values above and click Calculate to see your result instantly.
Quick reference
| Need | Settings |
|---|---|
| Reference / order codes | 8 chars, A–Z + 0–9, exclude look-alikes |
| Temporary passwords | 12–16 chars, full mixed set |
| Coupon codes | 6–8 chars, A–Z + 0–9 |
| Test data | Any length, 100 at a time |
Interpretation guide
| Length (62-char set) | Possible strings |
|---|---|
| 6 | 5.7 × 10¹⁰ |
| 8 | 2.2 × 10¹⁴ |
| 12 | 3.2 × 10²¹ |
| 16 | 4.8 × 10²⁸ |
Formula & methodology
Formula: Possible strings = (pool size)^length — 62 characters at length 8 gives 62⁸ ≈ 2.2 × 10¹⁴
- Pick the string length, how many strings you need, and the character pool.
- Each character is drawn independently with a cryptographically secure random source (no predictable seeds).
- Optionally exclude the look-alikes 0/O and 1/l/I for codes humans must read or type.
Worked example: an 8-character string over A–Z, a–z, 0–9 (62 characters) has 62⁸ ≈ 218 trillion possibilities — collisions are effectively impossible for everyday code generation.
Frequently asked questions
How do I generate a random string of numbers and letters?
Choose the length and character set above and click Generate. Each character is drawn independently from the pool with a cryptographically secure random source.
Are these strings secure enough for passwords?
Yes — they use the browser's crypto-grade randomness. For passwords, use 12+ characters of the full mixed set; for high-value secrets add symbols with a dedicated password manager.
Why exclude characters like 0, O, 1, l and I?
In most fonts they are nearly identical. For codes a human reads aloud or retypes (vouchers, license keys, references), removing them eliminates the most common transcription errors.
How unique are the generated codes?
An 8-character alphanumeric string has 218 trillion possibilities, so accidental duplicates are vanishingly rare — but if you need guaranteed uniqueness, deduplicate against your database on insert.
Is everything generated locally?
Yes — the strings are produced in your browser and never sent to a server, so they're safe to use for credentials and internal references.