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Verify passwords against bcrypt hashes by comparing plaintext passwords with stored bcrypt hash values. Supports all bcrypt variants ($2a$, $2b$, $2y$) and provides secure password verification for authentication systems.
Note: AI can make mistakes, so please double-check it.
Enter password and hash to verify
Common questions about this tool
Enter the plaintext password and the bcrypt hash. The verifier hashes the password with the same salt and cost factor from the hash, then compares the results. If they match, the password is correct.
The verifier supports all common bcrypt variants: $2a$ (original), $2b$ (corrected version), and $2y$ (PHP compatibility). All variants use the same algorithm but have minor implementation differences.
Yes, bcrypt is designed for password hashing with built-in salting and adaptive cost factors. Verification is secure and resistant to timing attacks. The algorithm is slow by design to prevent brute-force attacks.
Yes, as long as the hash is in standard bcrypt format ($2a$, $2b$, or $2y$ prefix), you can verify passwords regardless of which system generated the hash. Bcrypt is standardized and cross-platform compatible.
If verification fails, the password doesn't match the hash. This could mean the password is incorrect, the hash is corrupted, or there's a format mismatch. Double-check both the password and hash format for accuracy.
Learn what this tool does, when to use it, and how it fits into your workflow.
The Bcrypt Verifier checks whether a plaintext password matches a given bcrypt hash. It parses the hash, validates that it is in standard bcrypt format, reads the cost factor and variant, and then uses a cryptographic library in your browser to perform a secure comparison.
Bcrypt is one of the most widely used password hashing algorithms. It is designed to be slow and to include salts, making brute-force attacks harder. When you debug logins, migrate user accounts, or audit password storage, you often need a way to test whether a password and hash go together outside of the production system.
This tool solves that problem in a controlled environment. You enter the password and the bcrypt hash, optionally enable auto-trimming, and the verifier tells you whether they match. It also shows metadata about the hash, offers basic diagnosis hints when verification fails, and can request an AI-powered security analysis of the hash configuration.
The Bcrypt Verifier is for backend developers, security engineers, penetration testers, and anyone responsible for authentication systems. It assumes a beginner to intermediate understanding of passwords and hashing but presents information in simple language.
Bcrypt is a password hashing function built on the Blowfish cipher. Unlike fast hash functions such as SHA-256, bcrypt is intentionally slow and tunable. It uses a cost factor (also called work factor or rounds) that controls how many iterations are used. Higher cost means more time and CPU work per hash, which makes brute-force attacks more expensive. A related operation involves generating bcrypt hashes as part of a similar workflow.
A bcrypt hash has a fixed structure. It begins with an identifier such as $2a$, $2b$, $2x$, or $2y$. After that comes a two-digit cost factor, followed by a dollar sign, and then a 53-character string that encodes the salt and hash using a custom 64-character alphabet. In total, a standard bcrypt hash string is 60 characters long.
To verify a password, you must feed both the password and the full hash string into a bcrypt implementation. The library extracts the salt and cost from the hash, re-runs the bcrypt algorithm on the password, and compares the resulting hash to the stored one in a way that avoids timing leaks.
Manual verification is error-prone. Problems arise when hashes are malformed, when leading or trailing whitespace is accidentally added to passwords, or when cost factors are outside the recommended range. The Bcrypt Verifier encodes this knowledge in helper functions and user interface messages so that you can focus on the core question: does this password match this hash?
window.dcodeIO.bcrypt implementation for legacy support. If not available, it tries to import bcryptjs dynamically and exposes a minimal API for comparison and round extraction.$2a$, $2b$, $2x$, or $2y$), and that the length is exactly 60 characters. It then extracts the variant token and numeric cost.trim() before verification. This is useful when dealing with user input that may contain accidental spaces or line breaks.$2b$) and cost factor. The cost is shown both as the numeric exponent and in the form 2^{cost} to highlight its exponential effect.Debugging login failures: When a user reports that their password no longer works, you can test the password and stored bcrypt hash in this tool (using safe test data or in a secure environment) to see whether they match. For adjacent tasks, identifying hash types addresses a complementary step.
Validating password migration scripts: If you are migrating users between systems that both use bcrypt, you can spot-check a few hashes and passwords to make sure they survived the migration correctly.
Auditing password hash strength: By analyzing the cost factor and variant, you can decide whether your deployment uses a sufficiently strong configuration or if you should raise the cost for new hashes.
Teaching bcrypt behavior: Trainers can demonstrate how cost affects performance and how small input changes break matches, helping learners understand why bcrypt is effective for password storage.
Investigating suspected data corruption: If passwords suddenly stop matching, analysis can reveal whether hashes are malformed, truncated, or generated with unexpected parameters. When working with related formats, generating SHA-256 hashes can be a useful part of the process.
$2b$12$... and be 60 characters long.The hash analysis function first checks for an empty string and for length over the 200-character limit. It then applies a strict regular expression that enforces the structure $2[abxy]$dd$53chars, where dd is a two-digit cost and the tail uses the bcrypt character set.
If the hash fails this pattern, the function sets isValidFormat to false and chooses an error message based on obvious issues, such as a wrong prefix or incorrect total length. If the hash passes the regex, the function splits it on dollar signs to extract the variant and cost, parses the cost as a decimal number, and checks that it falls within the allowed range (4 to 31).
The verification function first validates that both password and hash are present, are strings, and within their respective length limits. It then applies optional trimming to the password if the auto-trim flag is enabled. Next, it calls the analysis function to get hash metadata.
If the hash is valid, it attempts to use the globally available bcrypt object to compare the password and hash synchronously. Any errors from the library that indicate missing or unloaded code are reported; other comparison errors are treated as simple mismatches. In some workflows, generating HMAC signatures is a relevant follow-up operation.
When comparison returns false and the hash is valid, the function tries an additional diagnostic check: if auto-trim is off, it trims the password and runs comparison again purely for diagnosis. If that trim check succeeds, it adds a message stating that a match is found after trimming whitespace. It also notes an empty password field or generic guidance about cost and variant mismatches when appropriate.
Finally, the function returns a structured result containing a boolean match flag, the metadata, an optional diagnosis array, and a timestamp. The UI uses this data to populate status cards and explanations.
| Cost factor | Relative work | Recommended usage |
|---|---|---|
| 4–8 | Low | Legacy systems, not recommended for new deployments |
| 9–12 | Medium | Common range for interactive logins |
| 13–16 | High | More secure, may be used for sensitive applications |
Protect real credentials: Avoid pasting live production passwords and hashes into the tool on shared or insecure machines. Use test data whenever possible.
Use strong cost factors: For new hashes, prefer a cost factor in the medium to high range that your infrastructure can handle without slowing logins too much. For related processing needs, calculating checksums handles a complementary task.
Align trim behavior: Ensure your application and this tool agree on how they handle whitespace. If trimming changes a non-match into a match, review your application’s input handling.
Check variant consistency: When migrating between languages or libraries, confirm that all systems support the same bcrypt variants ($2a$, $2b$, $2y$) and handle them correctly.
Do not lower cost to speed up tests: Fast bcrypt hashes are easier to brute-force. Keep production cost factors high even if local tests take slightly longer.
Remember that verification is one direction: This tool confirms whether a password matches a hash. It cannot reveal the original password from the hash if you do not already know it.
Rotate and upgrade over time: As computing hardware gets faster, consider increasing bcrypt cost factors for new hashes and gradually rehashing old accounts on login.
Use AI analysis as a guide, not a rule: The AI security insight can highlight potential weaknesses, but final decisions about configuration should involve your security policies and risk assessments.
Monitor library loading errors: If you see messages about failing to load the cryptographic library, refresh the page or try in a different browser. Verification requires that the bcrypt code load successfully.
Keep hashes confidential: Even though bcrypt is resistant to cracking, treat hashes as sensitive. Stolen hashes can still be attacked offline over long periods.
We’ll add articles and guides here soon. Check back for tips and best practices.
Summary: Verify passwords against bcrypt hashes by comparing plaintext passwords with stored bcrypt hash values. Supports all bcrypt variants ($2a$, $2b$, $2y$) and provides secure password verification for authentication systems.