What is the difference between Full URL and Single value mode?

Full URL mode (encodeURI/decodeURI) keeps : / ? & = # working as link structure and only fixes unsafe characters. Single value mode (encodeURIComponent/decodeURIComponent) encodes those characters too (%26, %3D, %3F), which is what one query value needs so its own & or = cannot split the link.

Why did decoding say the percent-encoding is invalid?

There is a broken percent sign in the text: a trailing %, a short %2, a non-hex %ZZ, or bytes that are not valid UTF-8. The tool explains the problem instead of guessing a half-decoded result.

Is URL encoding encryption or security?

No. Percent-encoding is transport formatting that anyone can reverse instantly. It hides nothing, so never put a password, API key or token in a URL expecting encoding to protect it.

Is anything uploaded?

No. Conversion runs in your browser tab with the built-in encodeURI/encodeURIComponent functions. Nothing is uploaded, stored or shared.

URL Encoder Decoder — Full URL or Single Value, Free

Free URL encoder and decoder. Encode a full URL with encodeURI or a single query value with encodeURIComponent, decode either way with plain-language errors for invalid percent-sequences. UTF-8 safe, fully local — nothing uploaded. Encoding is not encryption.