Plain Text
Base64
About Base64 Encoding
Base64 is a binary-to-text encoding scheme defined in RFC 4648. It represents binary data using 64 ASCII characters (A-Z, a-z, 0-9, +, /) plus = for padding, making it safe to transmit through text-based protocols.
What is Base64?
- Binary-to-text encoding - converts binary data into printable ASCII characters
- 6 bits per character - each Base64 character represents 6 bits of data
- ~33% size increase - 3 input bytes become 4 output characters
- Not encryption - anyone can decode it without a key
Base64 vs Base64URL
| Feature | Standard Base64 | Base64URL |
|---|---|---|
| 62nd character | + | - |
| 63rd character | / | _ |
| Padding | = (required) | Usually omitted |
| URL-safe | No | Yes |
| Used in | Email (MIME), data URIs | JWT tokens, URL parameters |
Common Uses
- Data URIs - embedding images and fonts directly in HTML and CSS
- Email attachments - MIME encoding for binary attachments in email
- JWT tokens - header and payload are Base64URL-encoded
- API authentication - HTTP Basic Auth encodes credentials in Base64