Question 1

What is URL encoding?

Accepted Answer

Percent-encoding (RFC 3986) replaces characters that are not allowed in a URL — spaces, &, =, ?, #, non-ASCII letters — with a % followed by the byte value in hex. A space becomes %20, & becomes %26 and é becomes %C3%A9 (its two UTF-8 bytes). It keeps a URL unambiguous so a & inside a search term is not mistaken for a parameter separator.

Question 2

encodeURI vs encodeURIComponent — which should I use?

Accepted Answer

Use encodeURIComponent (the default here) for a single value you are putting into a query string or path segment: it encodes reserved characters like / ? & = # too. Use encodeURI for a complete URL that already has its structure: it leaves those reserved characters alone and only encodes spaces, quotes and non-ASCII.

Question 3

Why do spaces sometimes become + instead of %20?

Accepted Answer

HTML form submissions use application/x-www-form-urlencoded, an older scheme where a space is a + sign. In a URL path %20 is the only correct form; in a query string both usually work, but a literal + in a value must then be encoded as %2B. Tick “Use + for spaces” to match form encoding.

Question 4

Why does decoding say malformed?

Accepted Answer

A % in the input is not followed by two hex digits — often because the text was decoded twice or contains a literal percent sign like “50%”. Encode literal percent signs as %25 before decoding, or decode only the part of the string that is actually encoded.

Question 5

Does this handle emoji and other languages?

Accepted Answer

Yes. Characters outside ASCII are encoded as their UTF-8 bytes, each as %XX, which is what every modern browser and server expects. An emoji typically becomes four %XX groups.

Character	Encoded	Component	Full URL
space	%20	✓	✓
&	%26	✓	—
=	%3D	✓	—
?	%3F	✓	—
/	%2F	✓	—
#	%23	✓	—
+	%2B	✓	—
%	%25	✓	✓
"	%22	✓	✓
é	%C3%A9	✓	✓
A–Z a–z 0–9 - _ . ~	unchanged	—	—

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