Hash Lookup
Reverse lookup a hash to find its plaintext. Checks MD5, SHA-1, and SHA-256 against a database of common passwords and strings. 100% client-side.
Warning: This hash was found in a common password database. If this is a password hash, the password is extremely weak and should be changed immediately.
This hash was not found in our database of common passwords. This could mean the original value is a strong, unique string.
Paste a hash below to look it up
Lookup Hash
Checks against ~10,000 common passwords & strings. All processing happens in your browser.
How Hash Lookup Works
Hash functions are one-way — you can't mathematically reverse them to get the original input. However, you can pre-compute hashes for known inputs (like common passwords) and build a lookup table.
This tool loads a database of ~10,000 commonly used passwords and strings, computes their MD5, SHA-1, and SHA-256 hashes entirely in your browser using the Web Crypto API, and checks if your hash matches any of them.
Paste Hash
Enter any MD5 (32 chars), SHA-1 (40 chars), or SHA-256 (64 chars) hash.
Local Computation
Your browser computes hashes for all entries in the database and compares.
Instant Result
If a match is found, the original plaintext is revealed instantly.
Why Hash Lookup Matters
Hash lookup tools help security professionals and developers audit password strength. If a password hash can be reversed using a common dictionary, that password is dangerously weak.
- Penetration testing: Check if leaked hashes correspond to weak passwords
- Security auditing: Verify that your users aren't using common passwords
- Education: Demonstrate why MD5 and SHA-1 are unsuitable for password storage
- Incident response: Quickly identify compromised accounts with weak passwords
Hash Algorithm Comparison
| Algorithm | Output Length | For Passwords? | Lookup Difficulty |
|---|---|---|---|
| MD5 | 32 hex chars | Never | Very Easy |
| SHA-1 | 40 hex chars | Never | Very Easy |
| SHA-256 | 64 hex chars | Not ideal | Easy (for common inputs) |
| bcrypt | 60 chars | Recommended | Very Hard |
| Argon2 | Variable | Best | Extremely Hard |
Frequently Asked Questions
What is a hash lookup?
A hash lookup (reverse hash search) checks a hash value against a pre-computed database of hash-plaintext pairs. If your hash matches a known entry, the original plaintext is revealed. This is how attackers crack weak passwords — by using massive rainbow tables of common passwords.
Is my hash sent to any server?
No. Everything runs 100% in your browser. The common password list is loaded into memory, hashed locally using the Web Crypto API, and compared entirely client-side. Your hash never leaves your device.
Why can't it find my hash?
The tool checks against ~10,000 common passwords and strings. If the original value is unique, complex, or uncommon, it won't be in the database. This is actually a good sign — it means the password is not trivially crackable via dictionary attack.
Can this crack bcrypt or Argon2 hashes?
No. Bcrypt and Argon2 use unique salts for each hash, making pre-computed lookup tables useless. This is exactly why they're recommended for password storage. Only fast, unsalted hashes like MD5, SHA-1, and SHA-256 are vulnerable to lookup attacks.