Developer Tools · 4 min read
URL Encoding Explained — What Is %20 and Why URLs Need It
You've seen %20, %3A, or %2F in URLs. This is URL encoding — a way to transmit special characters safely in a web address.
Common URL Encoded Characters
| Character | Encoded | Reason |
|---|---|---|
| Space | %20 | Spaces break URL parsing |
! | %21 | Special character |
# | %23 | Fragment identifier in URLs |
& | %26 | Parameter separator |
/ | %2F | Path separator |
: | %3A | Protocol separator |
= | %3D | Key-value separator |
? | %3F | Query string start |
@ | %40 | Used in email/auth |
Safe vs Unsafe URL Characters
Safe (no encoding needed): Letters A–Z, a–z, digits 0–9, and - _ . ~
Reserved (special URL meaning): : / ? # [ ] @ ! $ & ' ( ) * + , ; = — encode these when they appear in values (not as URL structure).
Everything else must be percent-encoded.
Frequently Asked Questions
Percent-encoding that converts special characters to % + two hex digits so they can be safely included in a URL. A space (ASCII 32 = hex 20) becomes %20.
Spaces aren't allowed in URLs per RFC 3986. %20 is the percent-encoded representation (hex 20 = decimal 32 = ASCII space character).
Spaces, <, >, #, %, {, }, |, \, ^, ~, and any character outside ASCII. Reserved characters like & = / must be encoded when used in query values.
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