URL Encoder/Decoder: Complete Guide 2026 — Percent Encoding Explained

Every URL is encoded. If you've ever seen %20 in a URL and wondered what it means, URL encoding (also called percent encoding) is the mechanism that allows browsers and servers to safely transmit special characters over HTTP. Characters That Must Be Encoded Character Encoded As Reason Space `%20` Spaces are separators in URLs `&` `%26` Query parameter separator `/` `%2F` Path separator `%` `%25` Escape character itself `+` `%2B` Reserved for spaces in query strings encodeURIComponent vs encodeURI // encodeURIComponent — for parameter values encodeURIComponent ( " hello world! " ); // "hello%20world%21" // encodeURI — for full URLs (preserves structure) encodeURI ( " https://example.com/a b " ); // "https://example.com/a%20b" Common Mistakes Double encoding: encodeURIComponent(encodeURIComponent("hello")) becomes "hello%2520" — encode once only Using + for spaces in paths: /users/john+doe — use %20 instead Not encoding Unicode: Always encode non-ASCII characters The Bottom Line Always e