What is URL encoding and why is it needed?

URLs can only contain a limited set of ASCII characters. Characters with special URL meaning (?, &, =, #, /) or characters outside ASCII (spaces, Unicode, emoji) must be percent-encoded: each byte is replaced with %XX (its hexadecimal value). A space becomes %20. Without encoding, special characters break URL parsing and can enable injection attacks.

What is the difference between %20 and + for spaces?

%20 is the RFC 3986 standard for a space in any URL component (path, query, fragment). The + sign encodes spaces only in application/x-www-form-urlencoded format (HTML form submissions). In URL query strings both are commonly accepted, but %20 is more correct. In URL path segments, only %20 is valid — a + in a path is a literal plus sign, not a space.

What characters must always be percent-encoded in URLs?

Reserved characters (special URL meaning — encode when used as data): ! # $ & ' ( ) * + , / : ; = ? @ [ ]. Unsafe characters: space, { } | \ ^ ` and all non-ASCII. Safe characters (never need encoding): A–Z, a–z, 0–9, - _ . ~. In JavaScript: use encodeURIComponent() for data values, not encodeURI() which skips encoding reserved characters.

How do I decode a URL with Chinese or other Unicode characters?

Modern browsers encode Unicode characters as percent-encoded UTF-8 bytes. '北京' in a URL → %E5%8C%97%E4%BA%AC. To decode: paste the percent-encoded URL into this tool's decode field. In JavaScript: decodeURIComponent('%E5%8C%97%E4%BA%AC') returns '北京'. International domain names (IDNs) like 例え.jp use Punycode encoding (xn--r8jz45g.jp) — a different system from percent-encoding.

URL Encoder Decoder – Encode & Decode URLs Online

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By Calcus Team

·Reviewed August 2026·Free · No signup · Browser-based

Mode: encodeURIComponent (parameters) encodeURI (full URL)

URL Parser

URL Builder

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encodeURI vs encodeURIComponent

✅ Last updated: August 12, 2026

Also searched as: url encoder decoder online free | url encoding tool | percent encode url | decode url online

encodeURI encodes a full URL — it leaves characters like :, /, ?, &, =, and # unencoded because they're valid URL structure characters. encodeURIComponent is more aggressive — it encodes everything except letters, digits, and - _ . ! ~ * ' ( ). Use encodeURIComponent for encoding individual query parameter values. Use encodeURI for encoding a complete URL.

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How To Url Encode A String?

Use the URL Encoder Decoder above — enter your values and get instant results. This free online tool calculates how to url encode a string without any download or signup required. Results update in real time as you type.

Url Decoder Free Online?

Use the URL Encoder Decoder above — enter your values and get instant results. This free online tool calculates url decoder free online without any download or signup required. Results update in real time as you type.

Why is space encoded as %20 or +?

Both %20 and + represent a space in URLs, but in different contexts. %20 is the percent-encoded form of space (ASCII 32) and is valid everywhere in URLs. The + sign as a space is only valid in query strings (application/x-www-form-urlencoded format), originating from HTML form encoding. In modern code, use %20 — it's unambiguous. + as space is a legacy convention from early web forms.

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URL Characters

%20 space

%26 & ampersand

%3D = equals

%2F / slash

%3F ? question

%23 # hash

%40 @ at