Question 1

What is a hash and why would I use one?

Accepted Answer

A hash is a fixed-length string generated from input data using a one-way mathematical function. Hashes are used for password storage, file integrity verification, digital signatures, and data deduplication. Changing even a single character in the input produces a completely different hash.

Question 2

Which hash algorithm should I choose?

Accepted Answer

SHA-256 is the best general-purpose choice — it is secure, widely supported, and produces a 64-character hex string. SHA-512 is even stronger but produces longer output. MD5 and SHA-1 are faster but considered cryptographically broken; use them only for non-security purposes like checksums or legacy compatibility.

Question 3

Can I reverse a hash back to the original text?

Accepted Answer

No. Hash functions are one-way by design. There is no mathematical way to recover the original input from a hash. The only way to find the original is by guessing (brute force) or using a precomputed lookup table (rainbow table), which is why salting is important for password hashes.

Question 4

Is my input data sent to a server?

Accepted Answer

No. All hashing is performed locally in your browser using the Web Crypto API (for SHA) and a pure JavaScript implementation (for MD5). Your data never leaves your device.

Algorithm	Output Size	Security	Best For
MD5	128 bits (32 hex)	Broken	Legacy checksums, non-security
SHA-1	160 bits (40 hex)	Broken	Legacy systems, Git commits
SHA-256	256 bits (64 hex)	Secure	Passwords, certificates, blockchain
SHA-512	512 bits (128 hex)	Very Secure	High-security applications

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