Generate Passwords Online

Password Generator - Create Strong Secure Passwords Online Free

Weak passwords remain the leading cause of account compromises and data breaches. Reused passwords, dictionary words, predictable patterns, and insufficient length make it trivial for attackers to gain access through brute force, credential stuffing, or dictionary attacks. XConvert's free Password Generator creates cryptographically strong random passwords entirely in your browser — your generated passwords are never transmitted, stored, or logged anywhere.

How to Generate Secure Passwords with XConvert (4 Steps)

1. Set your password length — Use the slider or input field to choose your desired password length. Longer passwords are exponentially harder to crack. A minimum of 16 characters is recommended for most accounts; 20+ characters for high-security accounts.
2. Select character types — Choose which character sets to include: uppercase letters (A-Z), lowercase letters (a-z), digits (0-9), and special symbols (!@#$%^&*). Enable all four for maximum entropy. You can also exclude ambiguous characters (like 0/O, 1/l/I) for easier manual entry.
3. Generate your password — Click "Generate" to create a random password. The entropy (in bits) is displayed alongside the password, showing its theoretical strength. Generate multiple passwords to choose one you prefer.
4. Copy and use — Click the copy button to place the password on your clipboard. Use it immediately in your password manager or account registration form. The password is not stored anywhere after you leave the page.

What is Password Entropy?

Password entropy is a measure of how unpredictable a password is, expressed in bits. It quantifies the size of the search space an attacker would need to exhaust in a brute-force attack. Higher entropy means more possible combinations and a stronger password. Entropy is calculated as log2(C^L), where C is the number of possible characters in the character set and L is the password length.

For example, a password using lowercase letters only (26 characters) at 8 characters long has log2(26^8) ≈ 37.6 bits of entropy. The same length using all printable ASCII characters (95 characters) has log2(95^8) ≈ 52.6 bits. Increasing the length to 16 characters with the full character set yields log2(95^16) ≈ 105.2 bits — well beyond the reach of any brute-force attack with current or foreseeable technology.

The key insight is that length contributes more to entropy than character set diversity. A 20-character password using only lowercase letters (log2(26^20) ≈ 94.0 bits) is stronger than a 12-character password using all character types (log2(95^12) ≈ 78.8 bits). This is why modern security guidance emphasizes length over complexity. However, using both length and a diverse character set provides the strongest passwords.

Comparison Table

Feature	XConvert Password Generator	1Password Generator	Bitwarden Generator	LastPass Generator
Price	Free	Requires subscription	Free (basic)	Free (basic)
Runs in Browser	✅	✅ (web vault)	✅ (web vault)	✅ (web vault)
No Account Required	✅	❌	❌	❌
Cryptographic RNG	✅	✅	✅	✅
Entropy Display	✅	❌	❌	❌
Custom Length	✅ (1-128)	✅ (8-100)	✅ (5-128)	✅ (1-99)
Exclude Ambiguous Chars	✅	✅	❌	❌
Passphrase Mode	✅	✅	✅	❌
Privacy (No Upload)	✅	❌	❌	❌
No Installation	✅	❌	❌	❌

Common Use Cases

1. Account registration — Generate a unique, strong password for every new account you create. Never reuse passwords across services. Pair each generated password with a password manager for secure storage.

2. Password manager seeding — When setting up a password manager for the first time, use the generator to create strong master passwords and individual passwords for each stored account. The entropy display helps you verify each password meets your security threshold.

3. API keys and tokens — Generate high-entropy random strings for API keys, authentication tokens, webhook secrets, and other machine-to-machine credentials. Use maximum length and all character types for these non-human-entered values.

4. Database and service credentials — Create strong passwords for database users, service accounts, SMTP credentials, and other infrastructure secrets. These passwords are typically entered once and stored in configuration, so length and complexity have no usability cost.

5. Wi-Fi network passwords — Generate a strong, memorable-enough password for your Wi-Fi network. Consider using passphrase mode for something guests can type more easily while maintaining good entropy. Share the password via XConvert's QR Code Generator.

6. Encryption passphrases — Generate passphrases for disk encryption (BitLocker, FileVault, LUKS), encrypted archives, and PGP/GPG keys. These require high entropy since they protect data at rest and may be targeted by offline brute-force attacks.

Technical Details

XConvert's Password Generator uses the Web Crypto API's crypto.getRandomValues() function, which provides cryptographically secure pseudorandom numbers generated by the operating system's entropy source. This is fundamentally different from Math.random(), which uses a deterministic PRNG that is predictable and unsuitable for security purposes. The Web Crypto API draws from the OS-level CSPRNG (Cryptographically Secure Pseudorandom Number Generator) — /dev/urandom on Linux, CryptGenRandom on Windows, and SecRandomCopyBytes on macOS — which is seeded by hardware entropy sources including interrupt timing, disk I/O patterns, and dedicated hardware random number generators.

The generation algorithm works by creating a typed array of random bytes, then mapping each byte to a character in the selected character set using rejection sampling. Rejection sampling is important for avoiding modulo bias — if the character set size does not evenly divide 256 (the range of a byte), a naive modulo operation would make some characters slightly more likely than others. The generator discards random bytes that fall outside the largest multiple of the character set size, ensuring perfectly uniform distribution across all characters. This is the same technique used by production cryptographic libraries.

The entropy calculation displayed alongside each password is computed from the character set size and password length using the formula L × log2(C). This represents the theoretical maximum entropy assuming the password is truly random, which it is when generated by a CSPRNG. Human-chosen passwords have far lower effective entropy due to patterns, dictionary words, and predictable substitutions. The generator also provides a qualitative strength rating (Weak, Fair, Strong, Very Strong) based on entropy thresholds aligned with current NIST guidelines. All generation happens client-side — your passwords are never transmitted over the network, stored in any database, or logged in any analytics system. The generated password exists only in your browser's memory until you navigate away or close the tab.

Tips for Best Results

1. Use at least 16 characters — Modern GPU-based cracking rigs can test billions of password hashes per second. A 16-character password with mixed character types provides over 100 bits of entropy, which is infeasible to brute-force.

2. Enable all character types — Using uppercase, lowercase, digits, and symbols maximizes the character set size and entropy per character. Only disable character types if the target system has restrictions.

3. Use passphrase mode for memorable passwords — When you need to type a password from memory (like a master password), use passphrase mode to generate a sequence of random words. Four to six random words provide excellent entropy while being easier to remember than random characters.

4. Never reuse generated passwords — Generate a unique password for every account and service. If one service is breached, your other accounts remain secure. Use a password manager to store them all.

5. Check the entropy display — Aim for at least 80 bits of entropy for standard accounts and 128+ bits for high-security applications like encryption keys, master passwords, and infrastructure credentials.

6. Exclude ambiguous characters when needed — If you need to read or type the password manually (e.g., entering a Wi-Fi password on a device), exclude characters that look similar in many fonts: 0/O, 1/l/I, 5/S. For sharing Wi-Fi passwords, generate a QR code instead.

Frequently Asked Questions

Are the generated passwords truly random?

Yes. The generator uses the Web Crypto API (crypto.getRandomValues()), which provides cryptographically secure random numbers from the operating system's entropy source. This is the same randomness source used by TLS, SSH, and other security-critical protocols.

Is my generated password sent to a server?

No. Password generation happens entirely in your browser. The password exists only in your browser's memory and is never transmitted, stored, or logged. You can verify this by generating passwords with your network connection disabled.

What password length should I use?

For most accounts, 16 characters with all character types is a strong baseline (approximately 105 bits of entropy). For high-security applications (master passwords, encryption keys, infrastructure credentials), use 20-24 characters or more. The entropy display helps you gauge strength.

What is the difference between a password and a passphrase?

A password is typically a random string of characters. A passphrase is a sequence of random words (e.g., "correct horse battery staple"). Passphrases are easier to remember and type while providing comparable entropy when using enough words. Four to six random words is a good target.

Why does the generator show entropy in bits?

Entropy in bits is the standard measure of password strength in information security. It represents the number of binary decisions an attacker would need to make in a brute-force search. Each additional bit doubles the search space. 80 bits is considered strong; 128 bits is considered infeasible to brute-force.

Can I generate passwords that meet specific requirements?

Yes. You can control the length, include or exclude each character type (uppercase, lowercase, digits, symbols), and exclude ambiguous characters. If a service requires at least one character from each type, the generator can enforce this constraint.

What is modulo bias and why does it matter?

Modulo bias occurs when mapping random bytes to a character set whose size does not evenly divide 256. A naive byte % charsetSize operation makes some characters slightly more probable. The generator uses rejection sampling to eliminate this bias, ensuring perfectly uniform character distribution.

How does this compare to my password manager's generator?

The cryptographic quality is equivalent — both use CSPRNGs. XConvert's generator adds entropy display, requires no account or installation, and runs entirely client-side. It is ideal for generating passwords when you do not have your password manager available or for creating the master password for a new password manager.

Can I generate multiple passwords at once?

Yes. Click the generate button multiple times to create several passwords. Each generation is independent and uses fresh random bytes. You can compare the generated passwords and choose the one you prefer.

Should I use special characters in my passwords?

If the target system allows them, yes. Special characters increase the character set size from 62 (letters + digits) to 95 (all printable ASCII), adding approximately 0.6 bits of entropy per character. However, some systems restrict which special characters are allowed. If you encounter issues, try generating with a reduced symbol set. For generating other types of unique identifiers, see XConvert's UUID Generator.