The ASCII control characters %00-%1F were originally designed to control hardware devices.
Control characters have nothing to do inside a URL.
| ASCII Character | Description | URL-encoding |
|---|---|---|
| NUL | null character | %00 |
| SOH | start of header | %01 |
| STX | start of text | %02 |
| ETX | end of text | %03 |
| EOT | end of transmission | %04 |
| ENQ | enquiry | %05 |
| ACK | acknowledge | %06 |
| BEL | bell (ring) | %07 |
| BS | backspace | %08 |
| HT | horizontal tab | %09 |
| LF | line feed | %0A |
| VT | vertical tab | %0B |
| FF | form feed | %0C |
| CR | carriage return | %0D |
| SO | shift out | %0E |
| SI | shift in | %0F |
| DLE | data link escape | %10 |
| DC1 | device control 1 | %11 |
| DC2 | device control 2 | %12 |
| DC3 | device control 3 | %13 |
| DC4 | device control 4 | %14 |
| NAK | negative acknowledge | %15 |
| SYN | synchronize | %16 |
| ETB | end transmission block | %17 |
| CAN | cancel | %18 |
| EM | end of medium | %19 |
| SUB | substitute | %1A |
| ESC | escape | %1B |
| FS | file separator | %1C |
| GS | group separator | %1D |
| RS | record separator | %1E |
| US | unit separator | %1F |