Question 1

Why does encoding a space produce %20 instead of a plus sign (+)?

Accepted Answer

%20 is the correct percent-encoding for a space per RFC 3986, and what this tool produces. The "+" convention comes from a different, older spec — application/x-www-form-urlencoded, used for HTML form submissions — and only applies there, not to URLs or query values in general. If you specifically need form-encoded output, this general-purpose encoder is not the right fit for that one character.

Question 2

What's actually being encoded here — is this the same as JavaScript's encodeURIComponent?

Accepted Answer

Yes, exactly — this runs encodeURIComponent, which percent-encodes every character outside the small "unreserved" set (letters, digits, and - _ . ~). That is deliberately more aggressive than encodeURI, which leaves things like / and & alone because it assumes you're encoding a whole URL rather than a single value. Use this tool for a value going into a query string or path segment, not for a complete URL.

Question 3

Will this re-encode a string that has already been percent-encoded?

Accepted Answer

Yes — it encodes every character it sees with no attempt to detect whether a % is already part of an encoded sequence, so re-running an already-encoded string through this tool turns its % signs into %25 and doubles the encoding. This is intentional (there's no reliable way to tell "already encoded" from "a literal % in your text" without guessing), so only encode each value once.

URL Encoder

Full Reserved-Character Coverage

Handles Large Text

Local Processing

Frequently Asked Questions