%20 Encoding

URL Encoding FAQ — Percent Encoding, Query Strings & Special Characters

Answers to common questions about URL encoding (percent encoding), query string parameters, reserved characters, and how to handle Unicode in URLs.

%20 URL Encode/Decode Free B64 Base64 Encode/Decode Free

Q1 What is URL encoding?

URL encoding (percent encoding) replaces unsafe characters in URLs with a % followed by two hexadecimal digits. For example, a space becomes %20, & becomes %26. This ensures URLs contain only valid ASCII characters. Use the URL Encoder/Decoder to encode any string instantly.

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Q2 Why do spaces become %20 in URLs?

Spaces are not valid in URLs according to RFC 3986. They must be encoded as %20 (the hex value of the ASCII space character, 0x20). In HTML form submissions with application/x-www-form-urlencoded, spaces are encoded as + instead — both are valid in query strings, but %20 is correct in the URL path.

Q3 What characters need URL encoding?

Characters that must be encoded include: spaces, < > # % { } | \ ^ ~ [ ] `, and non-ASCII characters (Unicode). Reserved characters (: / ? # [ ] @ ! $ & ' ( ) * + , ; =) need encoding when used outside their reserved purpose. Unreserved characters (A-Z, a-z, 0-9, - _ . ~) never need encoding.

Q4 What is the difference between encodeURI and encodeURIComponent?

encodeURI() encodes a full URI but preserves reserved characters (: / ? # & =) so the URL structure stays intact. encodeURIComponent() encodes everything except unreserved characters, making it safe for query parameter values. Rule: use encodeURIComponent for values, encodeURI for complete URLs.

Q5 How do I URL-encode in Python?

Use urllib.parse.quote(string) for path segments and urllib.parse.quote_plus(string) for query parameters (encodes spaces as +). To encode a full query string: urllib.parse.urlencode({"key": "value with spaces"}). To decode: urllib.parse.unquote(encoded).

Q6 How do I decode a URL?

Paste the encoded URL into the URL Decoder and click "Decode". In code: JavaScript — decodeURIComponent(encoded); Python — urllib.parse.unquote(encoded); CLI — use an online tool or Python one-liner.

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Q7 What is double URL encoding?

Double encoding happens when an already-encoded string gets encoded again: %20 becomes %2520. This breaks URLs and is a common bug. It occurs when a framework auto-encodes values that you already encoded manually. Fix: encode only once, or decode before re-encoding.

Q8 How do I encode Unicode in URLs?

Unicode characters in URLs are first encoded to UTF-8 bytes, then each byte is percent-encoded. For example, the letter U+00FC becomes UTF-8 bytes C3 BC, which are encoded as %C3%BC. Modern browsers display the Unicode character in the address bar but send the encoded form to the server.

Q9 What is the difference between %20 and + in URLs?

Both represent a space, but in different contexts. %20 is the standard percent encoding for spaces (valid everywhere in a URL). + is only valid as a space in query strings when using application/x-www-form-urlencoded format (HTML form submissions). In the URL path, + is a literal plus sign, not a space.

Q10 How do I URL-encode in JavaScript?

For query parameter values: encodeURIComponent('hello world & more'). For a complete URL: encodeURI('https://example.com/path with spaces'). For form data: use new URLSearchParams({key: 'value'}).toString() which handles encoding automatically.

Q11 Why do I need URL encoding for API calls?

Query parameters in API calls often contain special characters (& = ? #) that have special meaning in URLs. Without encoding, q=rock&roll would be interpreted as two parameters (q=rock and roll=). URL encoding ensures q=rock%26roll is sent as a single value.

Q12 What is percent encoding in HTTP?

Percent encoding is the official name for URL encoding (defined in RFC 3986). Each byte that needs encoding is represented as %HH where HH is the uppercase hexadecimal value. It ensures that all characters in a URI are valid ASCII and do not conflict with URI syntax delimiters.

Q13 How do I encode a URL in curl?

curl 7.18+ has --data-urlencode for POST form data: curl --data-urlencode 'name=John Doe' https://api.example.com. For URL path encoding, use --url with percent-encoded values or let your shell handle it. curl does not auto-encode query parameters in GET requests.

Q14 Can I have special characters in URL paths?

Yes, but they must be percent-encoded. Forward slashes (/) are path separators and should not be encoded in paths. Other special characters like spaces, ?, #, and non-ASCII characters must always be encoded. Modern web servers and frameworks handle encoding automatically in most cases.

Q15 What happens if I don't URL-encode parameters?

The URL may break or be misinterpreted. A & in a value would be treated as a parameter separator, a # would truncate the URL at a fragment identifier, and non-ASCII characters may cause encoding errors or mojibake. Always encode user-supplied input in URLs.

Q16 How do I encode a full query string?

In JavaScript: new URLSearchParams({key1: "val 1", key2: "val&2"}).toString(). In Python: urllib.parse.urlencode({"key1": "val 1", "key2": "val&2"}). These handle all encoding automatically. Or use the URL Encoder for quick manual encoding.

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Q17 What is URL encoding in HTML forms?

When an HTML form is submitted with method="GET" or POST with enctype="application/x-www-form-urlencoded", the browser automatically URL-encodes all form field values. Spaces become +, and special characters become %HH. This is the default encoding for HTML forms.

Q18 How long can a URL be?

The HTTP spec has no limit, but browsers and servers do. Chrome and Edge support URLs up to ~2 MB. Older IE versions had a 2,083 character limit. Most web servers default to 8-16 KB. Best practice: keep URLs under 2,000 characters for maximum compatibility. If you need more, use POST with a request body instead.

Q19 What is an Internationalized Resource Identifier (IRI)?

An IRI extends URIs to support Unicode characters directly (RFC 3987). Instead of percent-encoding every non-ASCII character, IRIs allow Unicode in the URL path. Browsers convert IRIs to URIs automatically for the network request. IRIs make URLs more human-readable for non-English content.

Q20 How do I URL-encode in PHP?

Use urlencode($string) for query parameter values (encodes spaces as +) or rawurlencode($string) for path segments (encodes spaces as %20). To decode: urldecode($string) or rawurldecode($string). Use http_build_query($params) for full query strings.