Encoding, hashing, and encryption get used interchangeably all the time, and it causes real problems -- like someone "encrypting" a password with Base64 and thinking it's protected, or trying to "decode" a SHA-256 hash back into the original text. They're three different tools that solve three different problems, and mixing them up usually means picking the wrong one.
Encoding: reversible, not secret
Encoding transforms data into a different format so it can be safely transmitted or stored -- nothing more. Base64 is the classic example: it turns arbitrary bytes (like an image or a binary file) into plain ASCII text so it can travel through systems that only handle text, like JSON payloads or email attachments.
Encoding is fully reversible, and reversing it requires no secret at all -- just the standard algorithm. Anyone can decode Base64 in one line of code. If you're using it to "hide" something, it isn't hidden.
Hashing: one-way, for verification
Hashing takes an input of any size and produces a fixed-length output, called a hash or digest. Feed it the same input twice, you get the same hash. Change even one character of the input, and the hash comes out completely different.
The critical property is that it's one-way -- you can't take a hash and recover the original data from it. That makes hashing useful for verifying that data hasn't changed (comparing file checksums) or for storing passwords (the server stores a hash of your password, not the password itself, and checks new attempts by hashing them and comparing).
MD5 and SHA-1 are still around but are considered broken for security purposes -- it's become computationally feasible to find two different inputs that produce the same hash. SHA-256 and SHA-512 are the current standard choices.
Encryption: reversible, but secret
Encryption is the one that actually keeps data confidential. It transforms data using a key, and getting the original data back requires that same key (or a related one, depending on the algorithm). Without the key, reversing it should be computationally infeasible.
This is what you want when data needs to stay secret but also needs to be readable again later by someone authorized -- a file you're storing, a message you're sending. AES-256 is the standard symmetric algorithm in wide use today; it's fast and, used correctly, hasn't been broken.
Picking the right one
The question to ask is what you actually need:
- Need to safely represent binary data as text, with no confidentiality requirement? Encoding.
- Need to verify data hasn't been tampered with, or store a password without keeping the plaintext? Hashing.
- Need to keep data secret now and get it back later? Encryption.
Using the wrong one for the job is a common source of real security bugs -- "encoding" a password and calling it secure, or hashing something you actually need to decrypt later. Knowing which category you're in before you write the code avoids both.
You can try all three directly: the Base64 Encoder/Decoder for encoding, the Hash Generator for MD5/SHA1/SHA256/SHA512 hashes, and the Text Encryption Tool for AES-256 encryption and decryption with a password.