URL Encode/Decode

URL (percent) encoding replaces characters that are unsafe in a URL — spaces, ampersands, slashes and non-ASCII — with a percent sign and hex code, so the URL stays valid.

When putting arbitrary text into a query string, a path segment or a form value, so special characters are not misinterpreted.

encodeURI keeps characters that are valid in a full URL, such as slashes and question marks, while encodeURIComponent encodes them too. Use component encoding for individual query values and path segments.

In the path and most contexts a space becomes %20, but in the query string of form submissions it is often encoded as a plus sign under the application/x-www-form-urlencoded rules. Both decode back to a space in the right context.

Encode the individual values you insert, such as a search term or a path segment, rather than the whole URL, otherwise you would also encode the separators like the colon and slashes that give the URL its structure.

Unreserved characters, namely the letters A to Z, the digits 0 to 9, and the hyphen, underscore, dot and tilde, never need percent-encoding. Everything else may need encoding depending on where it appears.