Password Generator

Password security is measured in bits of entropy, which quantifies the number of possible values an attacker would need to test to find the password by brute force. Entropy is determined by two factors: the size of the character set the password draws from, and the length of the password. Both matter, and they multiply each other rather than simply adding together.

A password of length L drawing from a character set of size C has C to the power of L possible values. A 12-character password using only lowercase letters (26 characters) has 26 to the power of 12, approximately 95 trillion possibilities. Adding uppercase letters, numbers, and symbols increases the character set to about 95 characters: 95 to the power of 12 is approximately 540 quadrillion. Extending to 20 characters with the full character set produces over 10 to the power of 39 possibilities - a number that exceeds the practical computation available to any attacker using any foreseeable technology.

NIST Special Publication 800-63B, the US federal standard for digital identity authentication, emphasizes password length over complexity and recommends against mandatory rotation schedules. The updated guidance reflects what security researchers have known for over a decade: long random passwords are more secure than short complex ones, and forced rotation creates predictable patterns (Summer2024!, Summer2025!) that reduce rather than improve security.

How Long Should a Password Be to Be Considered Secure

For accounts stored in a password manager where you never need to type the password manually, 20 characters or longer with all character types enabled is the current best practice. There is no practical performance cost to generating longer passwords for most applications, so maximizing length is the default approach when automated filling handles the typing.

For passwords you need to type occasionally - perhaps a VPN login used on a shared device, or a backup authentication code - 16 characters is the practical minimum that still provides strong security while remaining manageable to enter. Below 16 characters, brute-force attacks using dedicated hardware become feasible within timeframes measured in days rather than decades for high-value targets.

For master passwords that unlock password managers, the calculus changes. The master password must be memorized and typed regularly, but it also protects every other credential you have. A passphrase of five to six random common words (called a Diceware passphrase) is both memorizable and extremely strong: five random common words from a 7,776-word list provides approximately 64 bits of entropy, equivalent to a 10-character random password with full character set inclusion - and far easier to type correctly under pressure.

Humans are systematically bad at generating random passwords. Cognitive research on human attempts to generate random sequences consistently shows that people avoid long runs of the same digit, prefer certain numbers and letters over others, use personally meaningful information despite being told not to, and apply predictable complexity substitutions. Replacing vowels with numbers (p@ssw0rd), adding exclamation marks at the end (Password1!), and capitalizing the first letter are now among the first patterns that password cracking tools try, because they appear so frequently in leaked password databases.

A cryptographically secure random number generator has none of these biases. Every character is selected with mathematically equal probability from the available character set, independently of every other character in the sequence, with no awareness of what preceded it and no preference for any particular value. The result is a password that is genuinely random in the mathematical sense - not just surprising to a human observer, but resistant to statistical analysis.

ReverseToolkit's strong password generator uses window.crypto.getRandomValues(), which sources entropy from the operating system's cryptographic random number generator. This is the same entropy source used by OpenSSL, NSS, and every serious cryptographic library. It is emphatically not Math.random(), which is a pseudorandom number generator with a predictable internal state that should never be used for security-sensitive applications.

Password Generator That Does Not Store Passwords

Some password generator services log generated passwords for analytics or for "your convenience" features that let you retrieve previously generated passwords. This fundamentally defeats the purpose of generating a unique random password. A password that was transmitted to a server, even briefly, is no longer in your exclusive possession - it exists in logs, in transit records, and potentially in backups of those logs.

Browser-based generation using the Web Crypto API never transmits the generated value anywhere. The random bytes are selected locally on your device's sandboxed environment, the password is constructed and displayed locally in your device's memory, and when you navigate away or close the tab, the value is gone without any external record having been created. This is the only architecturally correct approach for a password generator that takes security seriously.

A 20-character random password is not meant to be memorized. The entire point of generating a random password is that it is not a word, a pattern, or a memorable sequence - it is a meaningless string of characters with maximum entropy. Managing these passwords requires a password manager, which is the application designed to store, secure, and auto-fill random credentials across all your accounts.

The workflow is straightforward: generate a random password using ReverseToolkit's random password generator, copy it, paste it simultaneously into the new account's password field and your password manager's new entry form, and confirm both before navigating away. The password manager stores an encrypted copy linked to the account URL and fills it automatically on future visits. You never need to know what the password is - only that it exists and is stored securely.

Popular password managers including Bitwarden (open source, available as a browser extension and mobile app), 1Password, and Dashlane all support this workflow. Bitwarden's open-source codebase allows independent security researchers to audit its encryption implementation, which is a meaningful advantage for users who want to verify rather than trust the security claims.

Email accounts are the highest-value targets for attackers because email is used to reset passwords for every other account. A compromised email account provides the keys to every service that uses that email for password recovery. Email passwords should be among the longest and most random you generate, and the account should have multi-factor authentication enabled with a hardware security key or authenticator app - not SMS, which is vulnerable to SIM-swapping attacks.

Financial accounts - banking, brokerage, cryptocurrency wallets - should use maximum-length generated passwords with all character types. These accounts have the most direct financial consequences from compromise. Some banking sites restrict password length to 16 or even 8 characters, which is a security shortcoming on their part. Work within their constraints by maximizing complexity within the allowed length.

Work and enterprise accounts often require passwords that meet specific policy requirements: minimum length, required character types, excluded characters, or maximum length (sometimes frustratingly short). Configure the generator's character set options to match the service's requirements and use the maximum allowed length. Many corporate accounts also require periodic rotation - generate a new random password each time rather than incrementing the old one.

Service accounts and API keys used in automation and infrastructure should be generated at maximum length (32 characters or longer when the service permits it) with full character set inclusion. These credentials are not typed by humans, so there is no usability tradeoff against maximum security. Rotate them regularly and store them in a secrets management system rather than in code repositories or configuration files.

The colored strength meter on most password forms (red, yellow, green) is a rough heuristic, not a precise security measurement. Most implementations check whether the password contains uppercase letters, lowercase letters, numbers, and symbols, and award a point for each. A password of "Aa1!" scores green on these meters while being catastrophically weak. "correct-horse-battery-staple" (the famous XKCD passphrase) fails most meters while being genuinely strong.

Ignore strength meters and focus on the actual security properties: length measured in characters, character set size, and randomness of generation. A 20-character password from a cryptographically secure generator is strong regardless of what color any meter assigns it.

Does the password generator transmit or store generated passwords?

No. Passwords are generated entirely locally on your device using the Web Crypto API. No value is transmitted to any server. The generated password exists only locally in your device's memory until you close the tab or navigate away, at which point it is gone with no external record created.

What is the most secure password length?

For accounts managed by a password manager where you never type the password manually, use 20 characters or longer with all character types enabled. For passwords you occasionally type, 16 characters is the practical minimum for strong security. For master passwords to password managers, use a Diceware passphrase of five or more random words instead.

Should I include special characters in every password?

Include all character types (uppercase, lowercase, numbers, symbols) when the service permits them, as this increases the character set size and improves security. When a service restricts certain characters, disable only those specific characters and compensate by increasing the password length. A 24-character alphanumeric password without symbols is stronger than a 12-character password with full special character inclusion.

How often should I change my passwords?

Current NIST guidance recommends changing passwords only when there is evidence of compromise, not on a fixed schedule. Forced regular rotation leads to predictable patterns that reduce security. Use unique random passwords from the start. Change them immediately if a service reports a data breach affecting your account, or if you have reason to believe your credentials were exposed.

Every account you create deserves a unique randomly generated password stored in a password manager. Start securing your accounts now using ReverseToolkit's secure password generator - nothing is stored, nothing is transmitted, and the generated password belongs entirely to you.