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Password Generator

Generate strong random passwords and estimate strength from length and character sets. Free online tool — no sign-up. Runs locally in your browser.

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How to use

Follow these steps for a clear answer.

1

Set length and character sets

Choose length and enable lower, upper, digits, and/or symbols.

2

Generate

Create a random password with Web Crypto when available.

3

Copy and store safely

Copy once into a password manager—nothing is uploaded.

Password generator & strength specification

Version 1.0.0 · Last reviewed 2026-07-29

Definition
A password generator creates random strings from chosen character sets; strength is estimated from length and alphabet size (entropy).
What it calculates
Random passwords from selected alphabets; entropy estimate bits ≈ length × log2(poolSize).
Inputs
  • Length
  • Character sets: lower, upper, digits, symbols
  • Optional password string for strength-only check
Outputs
  • Generated password
  • Estimated entropy (bits) and label
Formula
entropy ≈ L × log2(N) where N is the selected alphabet size

Generate a strong random password and see an entropy-based strength estimate. Everything stays on your device.

Tips

  • Prefer length over clever substitutions (P@ssw0rd is still weak).
  • Enable mixed character sets when a site allows them.
  • Store results in a password manager—do not paste secrets into shared docs.
Assumptions
  • Characters are drawn uniformly from the enabled sets.
  • Prefers crypto.getRandomValues when available.
  • Nothing is uploaded.
Units
  • Length: characters
  • Entropy: bits (estimate)
Boundary conditions
  • Length is clamped to a safe UI range (e.g. 4–128).
  • At least one character set must be enabled.
Example
Length 16, all sets → ~95-bit alphabet pool estimate when symbols included
Validation cases
  • password 'aaaa' length 4 lower-only → label very weak / low entropy
  • length 16 mixed sets → stronger entropy than length 8
Sources
  • NIST SP 800-63B (memorized secrets guidance)
  • Web Cryptography API getRandomValues
Last reviewed
2026-07-29
Calculation version
1.0.0
→ Base64 Decoder & Encoder › → Unix Timestamp Converter ›

Frequently asked questions

Key distinctions behind the tool.

Are passwords uploaded?

No. Generation and strength estimates run in your browser with the Web Crypto API when available.

How is strength estimated?

We estimate entropy from password length and the size of the selected character pool (lowercase, uppercase, digits, symbols). It is a guide, not a guarantee against all attacks.

Should I reuse passwords?

No. Use a unique password per site and a password manager.