Random String Generator
Generate random strings, codes, and placeholder values instantly. Customise length and character sets for perfect results every time.
Configure your options and press Generate to create random strings.
Entropy: 71.5 bits — pool: 62 chars
Advanced options
What is a Random String Generator?
Created & reviewed by Chad Solomon
Last reviewed 12 June 2026
A random string generator creates sequences of characters drawn from your chosen pools — uppercase, lowercase, numbers, symbols, or a custom set. Common uses include test data, placeholder tokens, coupon codes, game lobby codes, and unique identifiers. Strings are assembled in your browser using JavaScript's Math.random() (a pseudo-random generator), so nothing is sent to a server and your results stay private. For credentials that protect real accounts or systems, use a dedicated password manager that relies on a cryptographically secure source.
How to use this generator
- Set your string length using the slider (1–128 characters)
- Choose character types — uppercase, lowercase, numbers, symbols, or custom characters
- Configure advanced options like excluding similar characters and setting the count
- Generate and copy your random strings with one click
Common Uses for Random String Generation
Codes & Tokens
- Coupon and voucher codes
- Placeholder API keys for mock-ups
- Temporary access or invite codes
- Test data and placeholder IDs
Development & Programming
- Database record IDs
- Unique filename generation
- Test data creation
- Random string constants
Gaming & Applications
- Game lobby codes
- Invitation codes
- Temporary access codes
- Random seed generation
Demos & Documentation
- Sample configuration values
- Example tokens in tutorials
- Mock identifiers for screenshots
- Throwaway codes for demos
Understanding String Entropy
String entropy measures how many possible combinations exist for a given character pool and length, expressed in bits. The figures below show the theoretical maximum for the character set — the ceiling assuming a perfectly unpredictable source. The strings here are produced by Math.random(), a pseudo-random generator, so they do not reach that ceiling in practice and are not a security guarantee. Treat these numbers as an educational illustration of how length and pool size affect variety.
Entropy levels
- 60+ bits: Very Strong (vast variety)
- 40–59 bits: Strong (large variety)
- 25–39 bits: Moderate (decent variety)
- 15–24 bits: Weak (limited variety)
- <15 bits: Very Weak (easily exhausted)
Character pool sizes
- Lowercase only: 26 characters
- Mixed case: 52 characters
- Mixed + numbers: 62 characters
- Mixed + numbers + symbols: 88 characters
- Custom sets: Variable pool size
Practical Tips for String Generation
For Real Account Passwords
Do not use this tool for passwords that protect real accounts. Because it relies on Math.random(), the output is not suitable for credentials. Use a dedicated password manager such as Bitwarden or 1Password — these generate passwords from a cryptographically secure source and store them safely.
For Test Data & Placeholders
- • Use longer strings for more variety and fewer clashes
- • Include mixed case and numbers for realistic test IDs
- • Exclude similar-looking characters if typed by hand
- • Stick to alphanumeric for URL-safe codes
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How the Random String Generator Works
When you press Generate, the tool builds a character pool from your selected options — for example, enabling uppercase and numbers produces a 36-character pool (26 letters + 10 digits). It then picks each character of the output independently using Math.random(), which returns a floating-point value between 0 and 1. Multiplying by the pool size and rounding down gives an index into the pool, so every character has an equal chance of being chosen. The "Exclude similar characters" option removes i, l, 1, L, o, 0, O before building the pool, reducing visual ambiguity in printed or spoken codes. Custom characters override all toggles and let you define exactly which symbols are allowed.
Everything runs in your browser — no string is transmitted to a server. The entropy indicator is calculated as log₂(poolSize ^ length), giving you a practical measure of how many combinations are possible given your settings. For background on Math.random() and its limitations, see the MDN documentation for Math.random().
Example Random Strings
To illustrate what different settings produce, here are three strings generated during testing — each highlighting a distinct use case:
- mqvtjzrk — lowercase only, length 8. Useful for readable coupon codes or short internal IDs where visual ambiguity is not a concern.
- Kd7Pn2Rm4Qx1 — mixed case + numbers (alphanumeric), length 12. A common format for API tokens, invite codes, and database record keys that need to be URL-safe.
- R#9f!tW@2pZv — all character types including symbols, length 12. The higher pool size raises entropy substantially — good for placeholder passwords in test environments where a dedicated password manager is not in use.
String Combinations at a Glance
The table below shows the theoretical maximum number of possible strings and the corresponding entropy for three character-set configurations at common lengths — the ceiling for the character space, not a security rating. Character pool sizes used: lowercase only = 26, alphanumeric (A–Z + a–z + 0–9) = 62, all types (A–Z + a–z + 0–9 + symbols) = 88. Entropy = log₂(pool ^ length).
| Character set (pool size) | Length 8 | Length 12 | Length 16 |
|---|---|---|---|
| Lowercase only (26) | ≈ 2.1 × 10¹¹ / 37.6 bits | ≈ 9.5 × 10¹⁶ / 56.4 bits | ≈ 4.4 × 10²² / 75.2 bits |
| Alphanumeric (62) | ≈ 2.2 × 10¹⁴ / 47.6 bits | ≈ 3.2 × 10²¹ / 71.5 bits | ≈ 4.8 × 10²⁸ / 95.3 bits |
| All types (88) | ≈ 3.6 × 10¹⁵ / 51.7 bits | ≈ 2.2 × 10²³ / 77.5 bits | ≈ 1.3 × 10³¹ / 103.4 bits |
Frequently Asked Questions
Q.Are the generated strings safe to use as real passwords?
This tool uses JavaScript's Math.random(), which is a pseudo-random generator — not a cryptographically secure source. The strings are fine for test data, coupon codes, game tokens, and placeholder IDs. For passwords protecting real accounts or sensitive systems, use a dedicated password manager (such as Bitwarden or 1Password) that draws from a cryptographically secure random source.
Q.What character types can I include?
You can enable uppercase letters (A–Z, 26 characters), lowercase letters (a–z, 26 characters), numbers (0–9, 10 characters), and symbols (!@#$%^&*()_+-=[]{}|;:,.<>?, 26 characters). You can also supply a custom character list that overrides all toggles, or exclude visually similar characters like i, l, 1, L, o, 0, and O to make strings easier to read aloud or transcribe.
Q.Can I generate multiple strings at once?
Yes. Use the count control to produce 1, 2, 3, 5, 10, 20, or 50 strings in a single click. Each string is generated independently, so there is no guarantee against duplicates in very large batches, though repeats are extremely unlikely at longer lengths.
Q.What is string entropy and why does it matter?
Entropy (measured in bits) describes how many possible strings exist for a given character pool and length. A 12-character alphanumeric string (pool of 62) has about 71.5 bits of entropy — meaning there are roughly 3.2 × 10²¹ possible values. The higher the entropy, the harder it is to guess a specific string by brute force.
Q.What is the maximum string length?
The slider goes from 1 to 128 characters. For most purposes — unique IDs, coupon codes, session tokens — 16 to 32 characters is more than sufficient.
Q.Does the tool store or send my generated strings anywhere?
No. All generation happens in your browser. Nothing is transmitted to a server, logged, or stored. Once you close or refresh the page, the strings are gone.
Q.Why would I use 'Exclude similar characters'?
Characters like i, l, 1, L, o, 0, and O look nearly identical in many fonts. Excluding them makes strings safer to transcribe by hand or read aloud without errors — useful for invitation codes, licence keys, and other strings users might type manually.
Q.Can I use a custom character set?
Yes. Type any characters into the custom characters field and the tool will draw only from those — every other toggle is ignored. This lets you restrict output to, say, only hexadecimal digits (0–9, a–f) or a specific set of URL-safe symbols.