Paste the text into a browser-based hash generator and it computes the SHA-256 digest locally using the Web Crypto API built into your browser. The input never leaves your device, which is exactly what you want when the string you are hashing is an API key, a token or anything else sensitive.
SHA-256 turns any input into a fixed 256-bit digest, shown as 64 hex characters. The same input always produces the same hash, and changing a single character changes the whole output, which is why it is used for integrity checks, cache keys, content addressing and file verification. Browsers can compute it natively, so a client-side tool needs no server at all.
Older algorithms like MD5 and SHA-1 are broken for collision resistance and should not be used for anything security related, though MD5 still appears as a legacy checksum. And no fast hash, including SHA-256, is the right way to store passwords; password storage needs a deliberately slow algorithm like bcrypt or Argon2. For everything else, a local hash tool covers the everyday cases.
No. The hash is computed in your browser with the Web Crypto API, and the input is never transmitted.
No. It is a one-way function. Short or guessable inputs can still be found by brute force, so a hash of a weak secret is not protection.
Not for security. MD5 is broken for collision resistance. It only remains acceptable as a legacy, non-security checksum.