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ハッシュジェネレーター

任意のテキストからSHA-1、SHA-256、SHA-384、SHA-512ハッシュを生成。無料で登録不要。

About Hash Functions

Cryptographic hash functions generate a fixed-size hash value from input data. This online MD5 hash generator and SHA256 hash tool computes MD5, SHA-1, SHA-256, and SHA-512 hashes instantly in your browser. Hash functions are one-way: you cannot reverse a hash back to the original data. They're used for data integrity verification, password storage, digital signatures, file checksums, and deduplication. SHA-256 is recommended for security-sensitive applications, while MD5 remains useful for quick checksums despite being cryptographically broken.

Frequently Asked Questions

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How to Use

  1. Enter or paste your text in the input field
  2. Click 'Generate Hashes' to compute all hash values
  3. Toggle 'Uppercase' for uppercase hex output
  4. Copy any hash value with the copy button

Common Use Cases

  • Verifying file integrity with checksums
  • Password hashing for storage
  • Data deduplication
  • Digital signatures and certificates

Frequently Asked Questions

What is a hash function?
A hash function takes input data and produces a fixed-size string of characters (hash). The same input always produces the same hash, but you cannot reverse a hash back to the original data.
Which hash algorithm should I use?
SHA-256 is recommended for most purposes. SHA-512 offers more security. MD5 and SHA-1 are considered weak for security but are still used for checksums.
Is my data safe?
Yes. All hash computation happens in your browser using the Web Crypto API. No data is sent to any server.
What is the difference between MD5 and SHA-256?
MD5 produces a 128-bit (32 hex character) hash and is fast but cryptographically broken — collisions can be generated. SHA-256 produces a 256-bit (64 hex character) hash and is considered secure. Use SHA-256 for security, MD5 only for non-security checksums.
What is a hash collision?
A hash collision occurs when two different inputs produce the same hash output. MD5 and SHA-1 have known collision vulnerabilities. SHA-256 and SHA-512 have no known practical collisions and are considered collision-resistant.
What is a hash salt and why is it important?
A salt is random data added to the input before hashing, making each hash unique even for identical inputs. Salting prevents rainbow table attacks on password hashes. Always use a unique salt per password when storing hashed passwords.
When should I use bcrypt instead of SHA-256 for passwords?
Always use bcrypt (or Argon2, scrypt) for password hashing. SHA-256 is too fast, making brute-force attacks feasible. Bcrypt is intentionally slow and includes built-in salting, making it far more secure for password storage.
Can I reverse a hash back to the original text?
No. Hash functions are one-way by design. You cannot mathematically reverse a hash. Attackers use brute-force or rainbow tables to find inputs that match a hash, which is why strong passwords and salting are essential.