URL Encoder & Decoder

Encode special characters for URLs or decode percent-encoded strings. Switch between encode and decode modes with a single click. URL encoding and decoding happens instantly in your browser.

Loading editors...

Auto Sync

Automatically sync from left

Loading editors...

A search query ?q=hello world&page=1 needs to be ?q=hello%20world&page=1 before it leaves the browser. A redirect URL passed as a query param contains & and =that would otherwise be parsed as the outer URL's parameters — wrap it in percent-encoding and the meaning survives. A Korean filename 한글.pdf in a download URL becomes %ED%95%9C%EA%B8%80.pdf. This tool handles all three directions: paste, get the encoded or decoded version, copy.

Percent-encoding is the universal escape mechanism for URLs (RFC 3986). Without it, any character that has structural meaning in a URI (? # & = / +) becomes a parsing landmine. The sections below cover what gets encoded, the encodeURI vs encodeURIComponent trap, and the double-encoding bug that ships to production on a weekly basis.

How to Use

Select mode — Encode or Decode tab.
Enter data — Paste your text or URL-encoded string in the left editor.
Get result — Output appears instantly. Copy or download with one click.

Reserved vs unreserved characters (RFC 3986)

Unreserved (never encoded)

A-Z a-z 0-9 plus - . _ ~. Safe everywhere; encoders should leave these alone.

Reserved (encoded when literal)

: / ? # [ ] @ ! $ & ' ( ) * + , ; =. These carry structural meaning in URI syntax. Encode them when you want the literal character (e.g., an & in a query value, not the parameter separator).

Everything else (always encoded)

Spaces become %20 (or + in form bodies), non-ASCII Unicode becomes UTF-8 bytes percent-escaped (each byte as %XX), control characters become %00-%1F.

encodeURI vs encodeURIComponent

JavaScript exposes both. They differ on which characters they leave alone:

Function	Preserves	Use for
encodeURI()	`: / ? # [ ] @ ! $ & ' ( ) * + , ; =`	A full URL where structure is already correct
encodeURIComponent()	Only unreserved (`A-Z a-z 0-9 - . _ ~`)	A single query value, path segment, or fragment

Picking the wrong one is the canonical bug. encodeURI on a query value leaves & and = unescaped, breaking parsing. encodeURIComponent on a whole URL escapes :// and destroys the structure. Rule of thumb: encode each value with encodeURIComponent, then assemble the URL.

Quick reference: common encodings

Character	Encoded	Why encode
space	%20 (or + in form)	Spaces forbidden in URI
&	%26	Otherwise splits query params
=	%3D	Otherwise splits key=value
?	%3F	Otherwise starts query string
#	%23	Otherwise starts fragment
/	%2F	Otherwise splits path segment
한	%ED%95%9C	UTF-8 3-byte sequence escaped

Common pitfalls

Double encoding. Encoding an already-encoded string turns%20 into %2520. The decoded value is then %20 instead of a space. Usually caused by a framework that auto-encodes on the way out plus manual encoding in the controller.
+ vs %20. application/x-www-form-urlencoded (form POST bodies, query strings produced by HTML forms) encodes spaces as +. RFC 3986 URI encoding uses %20. Most decoders handle both, but + in a path segment is a literal +, not a space.
Forgetting non-ASCII paths. A static file named 한글.pdf on the filesystem must be requested as %ED%95%9C%EA%B8%80.pdf. Most browsers do this for you in the address bar; fetch() may not.
Hash never reaches the server. The #fragment portion is client-only. URL-encoding inside it changes routing but the server never sees it.
Percent-encoded slash in URL. %2F in a path is sometimes rejected by web servers (Apache) for security reasons, even though the spec allows it.

Related guide

Text encoding: Unicode and UTF-8

Why non-ASCII URL characters become 2-, 3-, or 4-byte percent-escape sequences — and how to debug the mojibake when something gets it wrong.

Frequently Asked Questions

Q: What characters need to be URL-encoded?

Anything outside the unreserved set A-Z a-z 0-9 - . _ ~ needs encoding when used as a query value, path segment, or fragment. That includes spaces, all punctuation, and every non-ASCII Unicode character (which becomes its UTF-8 bytes percent-escaped). Reserved characters (? # & = / + and others) only need encoding when you mean them literally, not structurally.

Q: What is the difference between encodeURI and encodeURIComponent?

encodeURI assumes the input is already a valid URI and leaves structural characters (: / ? # & = etc.) alone. encodeURIComponent assumes the input is a piece of a URI and encodes those characters too. Rule: encode each value with encodeURIComponent, then concatenate. This tool uses encodeURIComponent for maximum safety.

Q: Why does my URL contain %20 in some places and + in others?

Form submissions (application/x-www-form-urlencoded) encode spaces as +; URI percent-encoding uses %20. Most servers accept both in query strings, but + in a path segment is a literal plus sign, not a space. Mix the two in the same URL and eventually a parser will get it wrong.

Q: What is double encoding and how do I avoid it?

Double encoding happens when an already-encoded string runs through the encoder again — %20 becomes %2520. The fix is to track which layer owns encoding. Common offenders: middleware that auto-encodes plus manual encoding in the controller, or a value that already arrived encoded from a previous redirect.

Q: Is URL encoding the same as Base64 encoding?

No. URL encoding (percent-encoding) replaces specific characters with %XX hex codes and inflates size only for the encoded characters. Base64 converts arbitrary binary data to a 64-character ASCII alphabet and always inflates by 33%. URL encoding is for fixing structural collisions in a URI; Base64 is for embedding raw bytes in text channels.

Related Tools

Base64 Encoder & Decoder

Encode text to Base64 or decode Base64 strings in one unified tool.

QR Codes: A Complete Guide for Developers and Businesses11 min read Text Encoding Demystified: ASCII, Unicode, and UTF-8 for Developers11 min read

URL Encoder & Decoder

Encode special characters for URLs or decode percent-encoded strings. Switch between encode and decode modes with a single click. URL encoding and decoding happens instantly in your browser.

Loading editors...

Auto Sync

Automatically sync from left

Loading editors...

How to Use

Select mode — Encode or Decode tab.
Enter data — Paste your text or URL-encoded string in the left editor.
Get result — Output appears instantly. Copy or download with one click.

Reserved vs unreserved characters (RFC 3986)

Unreserved (never encoded)

A-Z a-z 0-9 plus - . _ ~. Safe everywhere; encoders should leave these alone.

Reserved (encoded when literal)

: / ? # [ ] @ ! $ & ' ( ) * + , ; =. These carry structural meaning in URI syntax. Encode them when you want the literal character (e.g., an & in a query value, not the parameter separator).

Everything else (always encoded)

Spaces become %20 (or + in form bodies), non-ASCII Unicode becomes UTF-8 bytes percent-escaped (each byte as %XX), control characters become %00-%1F.

encodeURI vs encodeURIComponent

JavaScript exposes both. They differ on which characters they leave alone:

Function	Preserves	Use for
encodeURI()	`: / ? # [ ] @ ! $ & ' ( ) * + , ; =`	A full URL where structure is already correct
encodeURIComponent()	Only unreserved (`A-Z a-z 0-9 - . _ ~`)	A single query value, path segment, or fragment

Quick reference: common encodings

Character	Encoded	Why encode
space	%20 (or + in form)	Spaces forbidden in URI
&	%26	Otherwise splits query params
=	%3D	Otherwise splits key=value
?	%3F	Otherwise starts query string
#	%23	Otherwise starts fragment
/	%2F	Otherwise splits path segment
한	%ED%95%9C	UTF-8 3-byte sequence escaped

Common pitfalls

Double encoding. Encoding an already-encoded string turns%20 into %2520. The decoded value is then %20 instead of a space. Usually caused by a framework that auto-encodes on the way out plus manual encoding in the controller.
+ vs %20. application/x-www-form-urlencoded (form POST bodies, query strings produced by HTML forms) encodes spaces as +. RFC 3986 URI encoding uses %20. Most decoders handle both, but + in a path segment is a literal +, not a space.
Forgetting non-ASCII paths. A static file named 한글.pdf on the filesystem must be requested as %ED%95%9C%EA%B8%80.pdf. Most browsers do this for you in the address bar; fetch() may not.
Hash never reaches the server. The #fragment portion is client-only. URL-encoding inside it changes routing but the server never sees it.
Percent-encoded slash in URL. %2F in a path is sometimes rejected by web servers (Apache) for security reasons, even though the spec allows it.

Related guide

Text encoding: Unicode and UTF-8

Why non-ASCII URL characters become 2-, 3-, or 4-byte percent-escape sequences — and how to debug the mojibake when something gets it wrong.

Frequently Asked Questions

Q: What characters need to be URL-encoded?

Q: What is the difference between encodeURI and encodeURIComponent?

Q: Why does my URL contain %20 in some places and + in others?

Q: What is double encoding and how do I avoid it?

Q: Is URL encoding the same as Base64 encoding?

Related Tools

Base64 Encoder & Decoder

Encode text to Base64 or decode Base64 strings in one unified tool.

QR Codes: A Complete Guide for Developers and Businesses11 min read Text Encoding Demystified: ASCII, Unicode, and UTF-8 for Developers11 min read