URL Encoder/Decoder

URL encoding — also called percent-encoding — converts characters that are unsafe or illegal in URLs into a safe ASCII representation. Defined in RFC 3986, it replaces problematic bytes with a percent sign followed by two hexadecimal digits: a space becomes %20, an ampersand becomes %26, and the letter é becomes %C3%A9. URLs were designed for a limited ASCII character set; spaces, accents, emoji, and many symbols must be encoded before they travel through browsers, servers, and APIs without breaking.

A URL encoder takes plain text and escapes reserved or non-ASCII characters. A URL decoder reverses the process. This is transport encoding, not encryption — anyone can decode a percent-encoded string instantly. The goal is compatibility: a query value like hello world must become hello%20world (or hello+world in form encoding) so the server reads one parameter value, not two tokens split at the space.

Why URL encoding exists

URIs can only contain certain unreserved characters: letters, digits, and a small set of symbols like -._~. Reserved characters — including ! * ' ( ) ; : @ & = + $ , / ? % # [ ] — have special meaning in different parts of a URL. Encoding ensures a dollar sign in a search query is data, not a delimiter confusion.

encodeURI vs encodeURIComponent

JavaScript provides two built-in functions. encodeURI encodes a full URI but preserves structure characters like slashes and question marks — use it when encoding an entire URL string. encodeURIComponent encodes everything except alphanumerics — use it for individual query parameter values, path segments, or any string that will be embedded inside a larger URL. This tool defaults to encodeURIComponent behavior because most users paste a value to encode, not a complete URL. Enable "Encode all characters" when even letters and digits must be percent-encoded.

Common use cases

• Query strings. Build ?q=hello+world&category=tech safely from user input.
• Form submissions. Encode field values for application/x-www-form-urlencoded bodies (spaces as +).
• API requests. Escape parameters in REST URLs and webhook callbacks.
• International URLs. Encode non-ASCII paths and filenames for sharing links with accented or CJK characters.
• Debugging. Decode broken links, inspect double-encoded strings, verify what a server actually received.

Why decoding sometimes fails

Malformed sequences cause errors: % must always be followed by exactly two hex digits. %ZZ and truncated %2 throw URIError. Double-encoding — encoding an already-encoded string — produces %2520 instead of %20, which decodes to a literal %20 rather than a space. Decode once, fix the source, encode once.

Why use an online URL encoder?

Every language has URL encoding libraries, but a browser-based encode url online tool is faster for one-off checks: paste an API parameter, verify a redirect URL, decode a query string from analytics, or test how emoji render when encoded. SuperTextTools runs locally with encodeURIComponent and decodeURIComponent — Unicode-safe, no deprecated escape(), nothing uploaded. Whether you need urlencode, urldecode, or percent encoding for a quick debug, the result stays on your device.