How long should my password be?

For random passwords, 16-20 characters with all four character sets enabled gives 100+ bits of entropy — strong enough for any account, including ones whose hashes might leak in a breach. PDFFlare's Password Generator defaults to 20 characters which lands at ~131 bits. For passphrases, 6 words from a large wordlist gives ~65 bits — plenty for personal accounts, easy to remember.

Is a passphrase stronger than a password?

It depends on length. A 6-word passphrase from PDFFlare's 1944-word list is ~65 bits — comparable to a 10-character random password from the full ASCII set. The advantage of a passphrase is memorability: you can actually remember it. For accounts behind a password manager, prefer random passwords (autofill handles typing); for accounts you log into manually, prefer passphrases.

Can two random passwords ever be identical?

Mathematically yes, practically no. PDFFlare's Password Generator uses crypto.getRandomValues() with rejection sampling — every password is independently uniform-random. For a 16-character password from the 94-char ASCII set, the chance of any two passwords colliding in a single-day batch of 1000 is roughly 1 in 10^25. Treat collision as impossible for any reasonable use.

Does PDFFlare see my generated passwords?

No. PDFFlare's Password Generator runs 100% client-side. The wordlist, the random number generation, the strength meter — everything happens in your browser. Nothing uploads, nothing logs. Safe for production credentials, root passwords, recovery codes, and any other sensitive value you'd rather not paste into a third-party tool.

Diceware is a passphrase technique invented by Arnold Reinhold in 1995: roll dice to randomly select words from a wordlist, repeat for each word. The math is what makes it strong — 7776 words on the standard EFF list = 12.92 bits per word; PDFFlare's 1944-word list gives ~10.9 bits per word. Modern diceware passphrase generators replace physical dice with the platform CSPRNG (crypto.getRandomValues in browsers) — the entropy math doesn't change.

May 4, 20269 min read

How to Generate Strong Password or Passphrase Online (Free)

You need a new password. Maybe a dozen new passwords. The easiest path is to generate strong password values from a random tool, copy each one into your password manager, and move on. Most generators do exactly that — and most of them either silently use Math.random() (predictable), phone home with telemetry on the values they produced, or give you weak defaults that look strong on the meter and fall apart against a real attacker. The version of password generation you use matters more than most people realize.

In this guide you'll learn how to generate strong password and passphrase values using PDFFlare's Password Generator — four modes (random, passphrase, pronounceable, PIN), 100% browser-based, cryptographically secure via the Web Crypto API. We'll cover what makes a password actually strong (entropy, not character variety), why diceware passphrases are the modern recommendation for memorable passwords, and the small mistakes that turn “random” passwords into trivially-cracked ones.

What Makes a Password Strong?

One concept: entropy. Measured in bits. Entropy is the logarithm-base-2 of the number of possible values your password could have been. A 4-digit PIN has 10⁴ = 10,000 possibilities, which is log₂(10,000) ≈ 13 bits of entropy. A 6-digit PIN has ~20 bits. A 16-character random password from the full ASCII printable set (~94 chars) has ~105 bits.

Bits matter because they directly map to how long it takes an attacker to brute-force the password. At 10 billion guesses per second (modest for modern GPU clusters), a password with N bits takes 2ᴺ⁻¹ / 10¹⁰ seconds on average:

40 bits: ~55 seconds — instant.
60 bits: ~16 hours — survives casual attacks.
80 bits: ~1900 years — strong enough for personal accounts.
100 bits: ~2 billion years — comfortable for high-value accounts.
128 bits: heat death of the universe.

The lesson: aim for 60-80 bits for accounts, 80+ bits for anything important, 100+ for cryptographic seeds.

Random Passwords vs Passphrases

Two different ways to reach the same entropy target:

Random password: 16 chars from the 94-character ASCII set = 16 × log₂(94) = ~105 bits. Compact, hard to type, impossible to memorize. Best stored in a password manager.
Passphrase: 6 random words from a ~2000-word list = 6 × log₂(2000) = ~66 bits. Drastically easier to type and memorize — at the cost of length (longer string, more typing).

For accounts you log into through a password manager, random wins on convenience (autofill handles the typing). For accounts you log into manually — your password manager master, your laptop, your encrypted disk — passphrases dominate. They're the answer to the famous XKCD comic's closing line: “Through 20 years of effort, we've successfully trained everyone to use passwords that are hard for humans to remember, but easy for computers to guess.”

How Much Entropy Do You Actually Need?

Real-world threat models vary:

40-50 bits:Resists script-kiddie password-spray attacks. OK for genuinely throwaway accounts (a forum you'll never visit again).
50-70 bits: Resists targeted online brute-force (where the attacker has to ask the server, and rate-limiting kicks in). OK for typical web accounts.
70-100 bits:Resists offline brute-force of leaked password hashes. Required for anything that might end up in a database breach (every account, really, since you don't know which sites store hashes properly).
100+ bits:Future-proof against quantum-era attacks (Grover's algorithm halves the effective bit count). Required for cryptographic seeds, recovery codes, master encryption keys.

Practical defaults: PDFFlare's Password Generator ships with a 20-character random password (~131 bits) and a 6-word passphrase (~65 bits) as defaults — both comfortably past the “survives a leaked-hash brute-force” threshold.

How to Generate Strong Password with PDFFlare

Step-by-step using PDFFlare's Password Generator:

Pick a mode from the four-button selector. Random is the safe default. Passphrase is for memorable credentials. Pronounceable is a halfway house. PIN is numeric only.
Configure options in the left panel. Random has length + character-set toggles + exclude similar/ambiguous. Passphrase has word count + separator + word case. Pronounceable has length + capitalization + digit/symbol suffix. PIN has length only.
Set bulk countfrom 1 to 100. Useful when you're seeding a password manager with unique passwords for many accounts at once.
Watch the strength meter update live. It shows entropy in bits, a qualitative label (Weak / Fair / Strong / Very Strong), and an estimated brute-force time at 10 billion guesses per second.
Show, copy, regenerate from the output panel. Show toggles between hidden dots and revealed text (privacy in shoulder-surfing situations). Copy grabs one row; Copy all grabs the entire batch as newline-separated text. Settings persist across visits via localStorage — the next time you need passwords, your last config is already loaded.

Using a strong password generator for new accounts

The right strong password generator workflow for a new account: open your password manager, click “Add item,” paste a 20-character random password from the generator into the password field, save. The password manager autofills future logins, so you never have to type or remember the value. PDFFlare's tool defaults match the standard advice — 20 characters, all four character sets enabled, exclude-similar off (since the manager handles typing). This is the pattern that scales: every account gets a unique 100+ bit password, and you only have to remember one master password.

Random password generator vs password manager built-ins

1Password, Bitwarden, LastPass, Dashlane, and the browser-built-in managers all include random password generators. They're fine. The reason a standalone random password generator like PDFFlare's still matters: bulk generation (your password manager probably tops out at one-at-a-time), passphrase mode with custom word counts and separators, configurable similar-character exclusion, and inspection of the generator's actual source — you can read PDFFlare's tool code, you cannot easily inspect a closed-source manager's RNG.

Diceware Passphrases (Memorable + Strong)

Diceware is a technique invented by Arnold Reinhold in 1995: roll five dice, look up the resulting 5-digit number in a 7776-entry wordlist, repeat for each word in your passphrase. The math: 6⁵ = 7776 outcomes per word = 12.92 bits per word. Six words gives 77 bits — solid for any account.

Modern diceware passphrase generators replace the physical dice with the platform CSPRNG (crypto.getRandomValuesin browsers). The math doesn't change — the entropy is in the wordlist size, not the source of randomness. PDFFlare's passphrase mode uses a 1944-word curated list (~10.9 bits per word). A 6-word passphrase = ~65 bits; an 8-word passphrase = ~87 bits.

Diceware passphrase generator: math, not magic

The diceware passphrase generator's strength comes from one specific property: every word is independently uniform-random from the full wordlist. If your generator biases word selection (favors common words, avoids two-word combinations that make grammatical sense, anything), the actual entropy is lower than the theoretical maximum. PDFFlare uses rejection sampling on top of crypto.getRandomValues() to guarantee unbiased uniform selection — every word in the wordlist is exactly 1/1944 likely on every draw.

PIN Mode: Numeric-Only Codes

For things that need a numeric-only credential — phone unlock codes, banking transaction PINs, voicemail access codes, two- factor recovery PINs — the PIN mode produces uniformly-random digit strings of configurable length. A pin code generator isn't glamorous, but it solves a real problem: when an interface restricts you to digits only, the standard random-password output won't fit. Defaults: 6 digits, configurable from 4 to 12.

Entropy math for PINs: each digit contributes log₂(10) ≈ 3.32 bits, so a 4-digit PIN is ~13 bits (10,000 possibilities), a 6-digit PIN is ~20 bits (1,000,000 possibilities), and a 12-digit PIN is ~40 bits. PINs alone aren't strong credentials for online accounts — they're acceptable only when paired with rate-limiting (banking apps lock out after 3-5 wrong attempts) or a second factor (your phone unlock PIN protects a device that already requires physical access). Don't use a PIN as a standalone password for anything online.

Pronounceable Passwords (Halfway House)

Sometimes you need a password you can read aloud or type quickly without it being completely random gibberish. Pronounceable mode generates passwords with alternating consonant-vowel syllables (CVCVCV). Examples: Bofidu47, Mukatare, Tiparemo!. Easier to type, easier to dictate over the phone, easier to glance-and-remember during a short login session.

The trade-off: pronounceable patterns have lower entropy per character than fully random. A 14-character pronounceable password is ~46 bits — fine for low-stakes accounts, weak for anything that might be brute-forced offline. Append 2 random digits and a symbol and you're back to ~55-60 bits. Best used for short-lived service accounts, internal tools, or anywhere a human will need to type the password and a password manager isn't available.

Common Password Mistakes

Treating “complex” as “strong.” Tr0ub4dor&3looks complex; it's about 28 bits — crackable in seconds. Length and randomness beat character-class variety every time.
Using personal patterns.Birthdays, pet names, sports teams, song lyrics — attackers maintain massive dictionaries of these and try them first. A password “you made up” is almost always weaker than a 6-word random passphrase.
Reusing passwords. One breached site exposes every account that shares the same password. Credential-stuffing attacks try leaked username+password pairs against every other major service. Unique passwords per account, generated by a real RNG, with a password manager remembering them.
Trusting tools that use Math.random(). Math.random() is predictable — given a few outputs, the next can be calculated. PDFFlare uses crypto.getRandomValues() with rejection sampling. Always verify your generator advertises a CSPRNG.
Generating passwords on a server you don't control. Many online password generators send your generated values back to the server (for “analytics,” ostensibly). The server now has your password. PDFFlare's password generator is 100% client-side — every byte stays in your browser.
Truncating to fit a length cap.Some sites impose a max length (12, 16, sometimes 8 chars). Generate a strong password that fits the cap rather than truncating a longer one — truncation removes entropy in a non-uniform way that's harder to reason about.

Privacy: Are Online Password Generators Safe?

The fundamental concern with any online password generator is whether the tool sees your generated values. PDFFlare's password generator runs entirely in your browser — every random byte comes from your machine's crypto.getRandomValues(), the wordlist is embedded in the page bundle, and the strength estimation is a pure function. Nothing uploads, nothing logs.

That matters specifically for:

Production credentials (root passwords, database superusers, API keys). The fewer parties that ever see these, the better.
Recovery codes and master passwords (your password manager vault, your encrypted disk, recovery seeds). These cannot be rotated cheaply if leaked.
Bulk-generated passwordsfor password- manager seeding. You don't want a third-party log of fifty passwords for fifty different accounts you own.

Pair the password generator with UUID Generator when you also need unique identifiers for the accounts you're seeding, or with Hash Generator when you need to derive a deterministic value from a generated password (e.g., a fingerprint hash for an internal audit log).

Related Tools

UUID Generator — generate v4 random UUIDs for account IDs, request IDs, or anywhere you'd want a globally unique identifier alongside a password.
Hash Generator — compute MD5, SHA-1, SHA-256, or SHA-512 hashes of any text. Useful for verifying password rotation, deriving fingerprints, or testing hash-based auth flows.
Base64 Encode / Decode — encode generated passwords for use in HTTP Basic Auth headers, environment variable values, or any context that requires ASCII-safe encoding.
URL Encode / Decode — escape generated passwords that need to live in a URL query string (database connection strings, OAuth redirect URIs).

Wrapping Up

Strong passwords are an entropy problem, not a complexity problem. 60+ bits resists casual attacks; 80+ bits resists offline brute-force of leaked hashes; 100+ bits is future- proof. Whether you reach those numbers via random characters or random words is up to you and the account's login workflow.

Generate your next batch with PDFFlare's Password Generator — four modes, live strength meter, bulk up to 100 at a time, all in your browser with cryptographic randomness. No signup, no watermarks, no telemetry. Just passwords.