Base64 Encode / Decode

Base64 encodes arbitrary binary data as ASCII text using 64 printable characters: A–Z, a–z, 0–9, +, and /, with =as padding. Every three bytes of input become four output characters, so encoded data grows by roughly 33% — trading size for the ability to embed binary content anywhere text is allowed. The other encodings here exist because that classic alphabet doesn't fit every situation.

The encoding zoo

• Base64 URL-safe swaps + and / for - and _, and drops the padding. JWTs use it because +/ would otherwise need percent-encoding inside a URL.
• Base32 uses only uppercase letters and digits (no 0/1, no I/O) so the output is case-insensitive and easy to dictate over the phone. TOTP secrets and onion addresses use it.
• Base58 drops visually-ambiguous characters (0OIl, +/) for hand-copyable identifiers. Bitcoin addresses are the canonical example.
• Hex is the lowest-common-denominator encoding — two characters per byte, no ambiguity, perfect for inspecting raw bytes.

When not to use it

None of these are encryption. They're fully reversible with no key, so never use them to "hide" secrets. Also avoid embedding large images in CSS — the file-size overhead and blocking parse cost usually outweigh the saved request.

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