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Standard Base64 encoding includes plus (+), slash (/), and equals (=) characters that require special URL-encoding when placed in query parameters or HTTP Authorization headers. RFC 7519 specifies Base64URL to avoid this.
| Character / Feature | Standard Base64 (RFC 4648 §4) | Base64URL (RFC 4648 §5) |
|---|---|---|
| Value 62 | + (plus) | - (minus) |
| Value 63 | / (slash) | _ (underscore) |
| Padding (=) | Mandatory (1 or 2 "=" characters) | Omitted (no padding in JWTs) |
| URL Safety | Requires URL encoding (%2B, %2F) | Native URL and header safe |
Encode and decode standard Base64 strings in Base64 Converter.
Hello World? + / =