A hash is a one-way digest
A cryptographic hash function converts an arbitrary byte sequence into a fixed-length digest. The same input bytes and algorithm produce the same digest. A small input change should produce a substantially different output.
Text is converted to UTF-8 bytes
The visible string is encoded as UTF-8 before hashing. Capitalization, whitespace, line endings, Unicode normalization, and invisible characters all affect the byte sequence and therefore the digest. A digest from another system matches only when its bytes and algorithm match exactly.
Hex and Base64 are representations
Hexadecimal and Base64 display the same digest bytes in different alphabets. SHA-256 always produces 32 digest bytes, shown as 64 hexadecimal characters or normally 44 padded Base64 characters. Converting the representation does not rehash or strengthen the digest.
Hashing is not encryption
A digest cannot be decrypted to recover the original in the way ciphertext can be decrypted with a key. However, attackers can guess inputs and compare hashes. Hashing predictable or low-entropy data does not make it secret.
Do not store passwords with plain SHA
Password storage needs a unique salt and a deliberately expensive password-hashing or key-derivation function such as one selected and configured by the security system responsible for authentication. A fast general-purpose SHA digest alone is unsuitable because guesses can be tested rapidly.
Integrity needs an authenticated source
A published file digest can reveal accidental corruption only if the expected digest comes from a trustworthy channel. If an attacker can replace both a file and its displayed digest, a matching hash proves nothing about origin. Authentication may require a digital signature or keyed construction designed for that purpose.
This tool hashes text in the current browser and does not intentionally upload it. It is not a password-storage system, encryption tool, digital-signature verifier, HMAC generator, file hasher, or security guarantee.