base64url is a Bash encoder/decoder for the base64url format (base64 with an URL and filename safe alphabet). It's described in the RFC 4648 (section 5):
This encoding may be referred to as "base64url". This encoding should not be regarded as the same as the "base64" encoding and should not be referred to as only "base64". Unless clarified otherwise, "base64" refers to the base 64 in the previous section.
This encoding is technically identical to the previous one, except for the 62:nd and 63:rd alphabet character, as indicated in Table 2.
Here's the table (Value / Encoding):
| V E | V E | V E | V E |
|---|---|---|---|
| 0 A | 17 R | 34 i | 51 z |
| 1 B | 18 S | 35 j | 52 0 |
| 2 C | 19 T | 36 k | 53 1 |
| 3 D | 20 U | 37 l | 54 2 |
| 4 E | 21 V | 38 m | 55 3 |
| 5 F | 22 W | 39 n | 56 4 |
| 6 G | 23 X | 40 o | 57 5 |
| 7 H | 24 Y | 41 p | 58 6 |
| 8 I | 25 Z | 42 q | 59 7 |
| 9 J | 26 a | 43 r | 60 8 |
| 10 K | 27 b | 44 s | 61 9 |
| 11 L | 28 c | 45 t | 62 - (minus) |
| 12 M | 29 d | 46 u | 63 _ (underline) |
| 13 N | 30 e | 47 v | |
| 14 O | 31 f | 48 w | |
| 15 P | 32 g | 49 x | |
| 16 Q | 33 h | 50 y | (pad) = |
For more details and examples, run base64url -h.
Copyright (C) 2023 Misaki F. <https://github.com/misaki-web/base64url
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.