Base64 Encode/Decode

What is Base64 encoding?

Base64 is a binary-to-text encoding that represents 8-bit bytes using a 64-character alphabet: the uppercase and lowercase letters A–Z and a–z, the digits 0–9, and the symbols + and /. Every three bytes of input become four characters of output, with = added as padding when the input length isn't a multiple of three. The encoding is reversible and lossless, which makes it a safe way to shuttle arbitrary binary data through text-only channels such as JSON, XML, email headers, or HTTP forms.

Standard vs URL-safe Base64

Standard Base64 uses + and /, but both characters have special meaning in URLs and file paths. RFC 4648 defines a URL-safe variant that substitutes - for + and _ for /, and typically strips the trailing = padding. This variant is what JSON Web Tokens (JWT), OAuth 2.0 bearer tokens, and many REST APIs use. Toggle the “URL-safe” option above to produce that format when encoding. The decoder accepts either variant automatically and re-pads as needed.

Common uses

Base64 shows up in many places you probably touch every day:

• Data URIs — embed small images or fonts directly in CSS or HTML using data:image/png;base64,… so no extra HTTP request is needed.
• JWT tokens — header, payload, and signature are each URL-safe Base64-encoded and joined with dots.
• HTTP Basic Auth — the Authorization header sends username:password as a Base64 string (note: this is encoding, not encryption — always use HTTPS).
• Embedded binary in JSON/XML — file uploads, cryptographic keys, certificates (PEM), and attachments in MIME email all rely on Base64 so that binary bytes survive text transport.
• Debugging & forensics — decoding a Base64 blob to hex is often the fastest way to inspect a file signature, a certificate, or an opaque token payload.

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