What is Hashing?

Hashing takes any piece of text or data and turns it into a fixed-length string of characters. That output is called a hash, and it's produced by a mathematical function — like SHA-256. The key thing to understand about hashing is that it's a one-way street. You can't reverse-engineer the original input from its hash. That's not a limitation; it's the whole point.

Key Properties of Hashing

• It's deterministic — the same input always produces the exact same hash, every single time, no matter what.
• The output length is always fixed for a given algorithm. SHA-256 always gives you a 256-bit hash, whether your input is one word or an entire book.
• Change a single character in your input and the hash comes out completely different. This is called the avalanche effect, and it's what makes hashing so useful for detecting tampering.

Common Uses for Developers

• When you download a file from a trusted source, there's often a SHA-256 hash listed next to it. Run the file through a hash generator — if your hash matches theirs, the file arrived intact. If it doesn't, something went wrong in transit (or worse).
• Storing passwords in plain text is a serious mistake that real-world breaches keep reminding us of. Instead, sites store a hash of the password. When you log in, the site hashes what you typed and compares it to the stored hash. The original password never needs to be stored anywhere.
• Hashing is fundamental to how blockchains work. Each block contains a hash of the previous block, which is how the chain becomes essentially tamper-proof — changing any block would invalidate every block after it.

Note on MD5: We don't support MD5 because it's cryptographically broken. It's possible to engineer two different inputs that produce the same MD5 hash — a collision — which makes it unreliable for any real security purpose.