What is Url decoding?

First, read previous url encoding article it helps you to understand decoding in brief. Basically url decoding is a reverse process of encoding, characters like alphanumeric ones a - z, A - Z, 0 - 9 and url safe character like -, _, ~, and ~ remain the same. But those characters which got encoded in hex after decoding they got their actual character identity. This is because url only accepts 8 bit characters only because Non-ASCII take more space (bytes) that's why url encoding is needed.

URL encoding table:

Dec Char Hex Enc Description
0 ^@ 00 blank Null (NUL)
1 ^A 01 blank Start of heading (SOH)
2 ^B 02 blank Start of text (STX)
3 ^C 03 blank End of text (ETX)
4 ^D 04 blank End of transmission (EOT)
5 ^E 05 blank Enquiry (ENQ)
6 ^F 06 blank Acknowledge (ACK)
7 ^G 07 blank Bell (BEL)
8 ^H 08 blank Backspace (BS)
9 ^I 09 blank Horizontal tab (HT)
10 ^J 0A blank Line feed (LF)
11 ^K 0B blank Vertical tab (VT)
12 ^L 0C blank New page/form feed (FF)
13 ^M 0D blank Carriage return (CR)
14 ^N 0E blank Shift out (SO)
15 ^O 0F blank Shift in (SI)
16 ^P 10 blank Data link escape (DLE)
17 ^Q 11 blank Device control 1 (DC1)
18 ^R 12 blank Device control 2 (DC2)
19 ^S 13 blank Device control 3 (DC3)
20 ^T 14 blank Device control 4 (DC4)
21 ^U 15 blank Negative acknowledge (NAK)
22 ^V 16 blank Synchronous idle (SYN)
23 ^W 17 blank End of transmission block (ETB)
24 ^X 18 blank Cancel (CAN)
25 ^Y 19 blank End of medium (EM)
26 ^Z 1A blank Substitute (SUB)
27 ^[ 1B blank Escape (ESC)
28 ^\ 1C blank File separator (FS)
29 ^] 1D blank Group separator (GS)
30 ^^ 1E blank Record separator (RS)
31 ^_ 1F blank Unit separator (US)
32 20 %20 Space
33 ! 21 %21 Exclamation mark
34 " 22 %22 Quotation mark/Double quote
35 # 23 %23 Number sign
36 $ 24 %24 Dollar sign
37 % 25 %25 Percentage sign
38 & 26 %26 Ampersand or And
39 ' 27 %27 Apostrophe/Single quote
40 ( 28 %28 Left parenthesis
41 ) 29 %29 Right parenthesis
42 * 2A %2A Asterisk
43 + 2B %2B Plus sign
44 , 2C %2C Comma
45 - 2D Hyphen/Minus
46 . 2E Full stop/Period
47 / 2F %2F Solidus/Slash
48 0 30 blank Digit zero
49 1 31 blank Digit one
50 2 32 blank Digit two
51 3 33 blank Digit three
52 4 34 blank Digit four
53 5 35 blank Digit five
54 6 36 Digit six
55 7 37 blank Digit seven
56 8 38 blank Digit eight
57 9 39 blank Digit nine
58 : 3A %3A Colon
59 ; 3B %3B Semicolon
60 < 3C %3C Less-than sign
61 = 3D %3D Equal/Equality sign
62 > 3E %3E Greater-than sign
63 ? 3F %3F Question mark
Dec Char Hex Enc Description
64 @ 40 %40 Commercial at/At sign
65 A 41 blank Latin capital letter A
66 B 42 blank Latin capital letter B
67 C 43 blank Latin capital letter C
68 D 44 blank Latin capital letter D
69 E 45 blank Latin capital letter E
70 F 46 blank Latin capital letter F
71 G 47 blank Latin capital letter G
72 H 48 blank Latin capital letter H
73 I 49 blank Latin capital letter I
74 J 4A blank Latin capital letter J
75 K 4B blank Latin capital letter K
76 L 4C blank Latin capital letter L
77 M 4D blank Latin capital letter M
78 N 4E blank Latin capital letter N
79 O 4F blank Latin capital letter O
80 P 50 Latin capital letter P
81 Q 51 blank Latin capital letter Q
82 R 52 blank Latin capital letter R
83 S 53 blank Latin capital letter S
84 T 54 blank Latin capital letter T
85 U 55 blank Latin capital letter U
86 V 56 blank Latin capital letter V
87 W 57 blank Latin capital letter W
88 X 58 blank Latin capital letter X
89 Y 59 blank Latin capital letter Y
90 Z 5A blank Latin capital letter Z
91 [ 5B %5B Left square bracket
92 \ 5C %5C Reverse solidus/Backslash
93 ] 5D %5D Right square bracket
94 ^ 5E %5E Circumflex accent/Caret
95 _ 5F blank Underscore/Low line
96 ` 60 %60 Grave accent
97 a 61 blank Latin small letter a
98 b 62 blank Latin small letter b
99 c 63 blank Latin small letter c
100 d 64 blank Latin small letter d
101 e 65 blank Latin small letter e
102 f 66 blank Latin small letter f
103 g 67 blank Latin small letter g
104 h 68 blank Latin small letter h
105 i 69 blank Latin small letter i
106 j 6A blank Latin small letter j
107 k 6B blank Latin small letter k
108 l 6C blank Latin small letter l
109 m 6D blank Latin small letter m
110 n 6E blank Latin small letter n
111 o 6F blank Latin small letter o
112 p 70 blank Latin small letter p
113 q 71 blank Latin small letter q
114 r 72 blank Latin small letter r
115 s 73 blank Latin small letter s
116 t 74 blank Latin small letter t
117 u 75 blank Latin small letter u
118 v 76 blank Latin small letter v
119 w 77 blank Latin small letter w
120 x 78 blank Latin small letter x
121 y 79 blank Latin small letter y
122 z 7A blank Latin small letter z
123 { 7B %7B Left curly bracket
124 | 7C %7C Vertical line/Vertical bar
125 } 7D %7D Right curly bracket
126 ~ 7E blank Tilde
127 DEL 7F blank Delete (DEL)