Base 64 Encoder & Decoder
Encodes or decodes a string or a binary file so that it conforms to the Base64 Data Encodings specification (RFC 4648).
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Base64 Encoding Explained
What is Base64 and why is it used?
Base64 is a way of representing arbitrary binary data using only 64 printable ASCII characters. It is specified in RFC 4648. Base64 is not encryption: it hides nothing.
How does it work?
The input is processed three bytes at a time. Three bytes (24 bits) are split into four groups of 6 bits, and each 6-bit value (0-63) is looked up in the alphabet. So every 3 input bytes become 4 output characters.
The Base64 alphabet
| Value | Char | Value | Char |
|---|---|---|---|
| 0-25 | A - Z |
26-51 | a - z |
| 52-61 | 0 - 9 |
62/63 | + / / (standard), - / _ (URL-safe) |
Padding
When input length is not a multiple of 3, padding with = makes the encoded length a multiple of 4.
Common uses
- E-mail attachments (MIME)
- HTTP Basic authentication
- JSON Web Tokens (base64url)
- Certificates and keys in PEM format
- Data URIs in CSS and HTML