What's the difference between %20 and + for spaces?

Both represent spaces. %20 is used in URL paths (RFC 3986). + is used in query strings (HTML forms). Most servers accept both, but %20 is more universal.

Do I need to encode the entire URL?

No. Only encode query parameter values and path segments with special characters. Structure characters like :, /, ?, & should remain unencoded.

Why are my API requests failing with special characters?

You likely need to URL-encode query parameters. Characters like &, =, and # have special meaning in URLs.

URL Encode/Decode

Percent-encode or decode URLs and query string parameters.

Plain Text

Encode →← Decode

URL Encoded

What is URL Encoding?

URL encoding (percent-encoding) replaces unsafe characters with % followed by two hex digits. Defined in RFC 3986. Required because URLs can only contain ASCII characters, and certain characters like &, =, ?, / have special meaning. For example, a space becomes %20 and & becomes %26.

Characters That Need Encoding

Space → %20 (or +), & → %26, = → %3D, ? → %3F, # → %23, / → %2F, + → %2B, @ → %40, : → %3A. Note: encodeURIComponent() encodes everything except A-Z a-z 0-9 - _ . ~ ! * ' ( )

// JavaScript
encodeURIComponent("hello world&foo=bar")
// "hello%20world%26foo%3Dbar"

decodeURIComponent("hello%20world%26foo%3Dbar")
// "hello world&foo=bar"

// Python
from urllib.parse import quote, unquote
quote("hello world&foo=bar")

encodeURI vs encodeURIComponent

encodeURI encodes a full URL but preserves :/?#[]@!$&'()*+,;= since they're valid in URLs. encodeURIComponent encodes everything except unreserved chars — use it for query parameter values. Common mistake: using encodeURI for query params leaves & and = unencoded.

Percent-Encoding Reference Table

Common characters and their percent-encoded values. encodeURIComponent() encodes all of these; unreserved characters (A-Z a-z 0-9 - _ . ~) are never encoded.

Character	Name	Encoded
(space)	Space	%20 (or +)
!	Exclamation	%21
"	Quote	%22
#	Hash / fragment	%23
$	Dollar	%24
%	Percent	%25
&	Ampersand	%26
'	Apostrophe	%27
(	Open paren	%28
)	Close paren	%29
*	Asterisk	%2A
+	Plus	%2B
,	Comma	%2C
/	Slash	%2F
:	Colon	%3A
;	Semicolon	%3B
=	Equals	%3D
?	Question mark	%3F
@	At sign	%40
[	Open bracket	%5B
]	Close bracket	%5D

Frequently Asked Questions

What's the difference between %20 and + for spaces?: Both represent spaces but in different contexts. %20 is used in URL paths (RFC 3986). + is used in query strings (application/x-www-form-urlencoded, from HTML forms). Most servers accept both, but %20 is more universal.
Do I need to encode the entire URL?: No. Only encode the parts that might contain special characters — typically query parameter values and path segments. The structure characters (:, /, ?, &, =) should remain unencoded for the URL to work.
Why are my API requests failing with special characters?: You probably need to URL-encode your query parameters. Characters like &, =, and # have special meaning in URLs. Use encodeURIComponent() on each parameter value before building the URL.

Guides

URL Encode Query String Parameters URL Decode Online URL Encode Special Characters URL Encode Spaces — %20 vs +encodeURI vs encodeURIComponent URL Encode in JavaScript

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