Question 1

Why do some URLs have %20 and others have plus signs?

Accepted Answer

Both encode spaces but apply in different contexts. %20 is the modern URL-safe encoding used in paths and query strings. The plus sign is a legacy encoding used specifically in application/x-www-form-urlencoded form submissions. They are interchangeable in most modern systems, but this tool produces %20 because encodeURIComponent (the JavaScript primitive used here) outputs %20.

Question 2

What characters are safe to leave unencoded?

Accepted Answer

Letters, digits, and the characters -_.~ are always safe in URLs. Everything else should be percent-encoded when used in paths, query strings, or fragment identifiers. The exact set of safe characters varies slightly between contexts (paths vs query strings vs fragments), but the conservative approach of percent-encoding everything outside [A-Za-z0-9-_.~] always works.

Question 3

When should I use encodeURI vs encodeURIComponent?

Accepted Answer

encodeURI is for whole URLs and preserves the colon, slash, question mark, hash, ampersand, equals, and other characters that have structural meaning in URLs. encodeURIComponent is for components (query-string values, path segments) and encodes everything except [A-Za-z0-9-_.~]. This tool uses encodeURIComponent semantics, which is what you want for encoding arbitrary text to put in a URL.

Question 4

Does this handle Unicode characters?

Accepted Answer

Yes. Non-ASCII characters are converted to UTF-8 byte sequences and each byte is percent-encoded. So 'café' becomes 'caf%C3%A9' (the é is U+00E9 which is two UTF-8 bytes: 0xC3 0xA9). Decoding works in reverse. Most modern systems use UTF-8 percent encoding, but legacy systems sometimes use other encodings; if a decoded value looks garbled, the URL may have been encoded with a non-UTF-8 character set.

URL Encoder and Decoder (Percent-Encoding)

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