Question 1

What is a hash function?

Accepted Answer

A hash function takes input data of any size and produces a fixed-size output (the hash or digest). The same input always produces the same output, but it is practically impossible to reverse the process — you cannot recover the original data from the hash.

Question 2

Which hash algorithm should I use?

Accepted Answer

For security purposes (password hashing, digital signatures), use SHA-256 or SHA-512. MD5 and SHA-1 are considered broken for security use but are still fine for checksums and non-security applications like file integrity verification.

Question 3

Is MD5 still safe to use?

Accepted Answer

MD5 is cryptographically broken — collision attacks are practical. Do not use MD5 for security. However, MD5 is still commonly used for non-security checksums, cache keys, and file deduplication where collision resistance is not critical.

Question 4

Is my data sent to a server?

Accepted Answer

No. All hashing is performed entirely in your browser using the Web Crypto API (SubtleCrypto). Your data never leaves your device.

Algorithm	Output	Security	Use Case
SHA-256	256 bits (64 hex)	Strong	General purpose, Bitcoin
SHA-512	512 bits (128 hex)	Strong	High security, certificates
SHA-1	160 bits (40 hex)	Weak	Git commits (legacy)
MD5	128 bits (32 hex)	Broken	Checksums, cache keys

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