Random String Generator - Create Alphanumeric Strings
Build 1-256 character random strings with custom pools and unique filtering in batches of 100,000 at once.
Need login credentials with symbols and live entropy scores? Switch to our Random Password Generator.
🔒 Data Safety: We process everything securely and never store or share it.
How to Use
- Specify your character length (1 to 256) and string count (up to 100,000 in one run) above.
- Check Lowercase, Uppercase, or Numbers below, and type any extra characters into the Custom Characters box.
- Toggle No Duplicates or Exclude Similar as needed, and pick an output delimiter from the Separator menu.
- Click "Generate" to build your random strings, then copy or download the results from the output box.
Options Explained
- Custom Characters (Optional): Add extra symbols, punctuation, or Unicode characters to your active pool alongside the checked character sets. Uncheck Lowercase, Uppercase, and Numbers to generate strings exclusively from your own custom character list.
- Lowercase (a-z) / Uppercase (A-Z) / Numbers (0-9): Include 26 lowercase letters, 26 uppercase letters, and 10 digits in any combination (up to 62 alphanumeric characters).
- No Duplicates (Unique): Guarantee that every string in your batch is distinct, provided total possible combinations cover your requested quantity.
- Exclude Similar (0O1lI): Filter out visually ambiguous characters (0Oo1lI|) from both standard sets and custom characters to prevent reading errors.
- Separator: Separate generated strings by a newline, comma, space, semicolon, or pipe for multi-line lists or inline arrays.
Key Features
- Generate 1 to 100,000 random strings per batch across custom lengths from 1 to 256 characters.
- Track active unique character counts and exact mathematical combination totals (Pool^Length) on the live counter bar.
- Normalize custom pools with NFC and Intl.Segmenter to support symbols, international scripts, and emojis without broken surrogates.
- Enforce non-repeating output via No Duplicates (Unique) with automatic combination checks and hybrid index-space sampling.
- Deduplicate overlapping characters and apply Exclude Similar (0Oo1lI|) filtering across both alphanumeric sets and custom inputs.
- Draw unbiased strings via 32-bit Web Crypto CSPRNG rejection sampling and five delimiters with zero server storage.
About This Online Random String Generator
Across lengths from 1 to 256 characters, this random string generator builds up to 100,000 strings per batch. Web Crypto CSPRNG sampling and grapheme-safe Unicode pools power every run alongside unique filtering and custom delimiters.
Developed and maintained by the PU Tools team, this tool gives you fast, accurate, safe, and easy results in just a few clicks.
Common Use Cases
- Promo, Voucher, and Coupon Codes: Combine uppercase letters and digits with Exclude Similar and No Duplicates to issue unambiguous, non-repeating discount codes.
- Verification Tokens and Reference IDs: Create 32 to 256-character alphanumeric or custom hexadecimal strings for session tokens, order references, and webhook secrets.
- Database Boundary and Unicode QA: Generate exact 255 or 256-character strings and custom UTF-8 emoji payloads to stress-test database VARCHAR column limits.
Example Input and Output
Example Input
String Length: 12 Quantity: 5
Options used: Custom Characters (Optional): OFF | Lowercase (a-z): ON | Uppercase (A-Z): ON | Numbers (0-9): ON | No Duplicates (Unique): ON | Exclude Similar (0O1lI): ON | Separator: New Line
Example Output
v8Kp3nTx6Wq2 H4mZ9cBr5Yd7 f3Gs7wJn2Qx9 M6tC8pVk4Lz3 b9Dr2hFy7Nu5
Each line displays a unique 12-character alphanumeric string with all look-alike characters removed from the pool.
Frequently Asked Questions
What string lengths and batch quantities does this generator support?
Each batch builds between 1 and 100,000 strings with lengths ranging from 1 to 256 characters. That span covers single-character draws, coupon codes, API tokens, and 255-character database VARCHAR column limits.
How can I generate hexadecimal, binary, or custom-only strings without standard letters?
Uncheck Lowercase, Uppercase, and Numbers, then type your exact character set into the Custom Characters box. Enter 0123456789abcdef for lowercase hex, 01 for binary, ACGT for DNA sequences, or any Unicode symbols.
How does the live counter calculate unique pool size and total combinations?
The counter deduplicates your active sets with a Set and raises that pool size to your length. Using BigInt math, it displays exact Pool^Length integers or switches to scientific notation above 9 quadrillion.
How does No Duplicates (Unique) guarantee distinct strings without freezing my browser?
Before generating, the engine verifies that total possible combinations (Pool^Length) are at least your requested quantity. Dense small pools use partial Fisher-Yates index shuffling, while large pools track unique picks with a Set.
Does Exclude Similar (0O1lI) also filter characters entered in the Custom Characters box?
Yes, enabling Exclude Similar strips all seven look-alike characters (0Oo1lI|) from both standard and custom inputs. Any repeated characters typed into Custom Characters are also deduplicated so every symbol keeps equal selection odds.
How does the tool handle multi-byte emojis and accented letters in Custom Characters?
Custom input is normalized to Unicode NFC and segmented into full grapheme clusters via Intl.Segmenter. Composite emojis and accented letters stay whole as single pool entries instead of splitting into broken surrogates.
How are random strings sampled, and is any generated data sent to a server?
No data ever leaves your device because every string is generated locally in your browser RAM. Buffered 32-bit Web Crypto CSPRNG (crypto.getRandomValues) with rejection sampling eliminates modulo bias with zero server storage.