URL Encoder & Decoder

encodeURI is meant for an entire URL, so it leaves the characters that have structural meaning (: / ? # [ ] @ & = + $ ,) untouched. encodeURIComponent is meant for a single piece of a URL, such as one query-string value, so it encodes those characters too. Rule of thumb: use encodeURIComponent for individual values you are slotting into a URL, and encodeURI only when you have a whole URL you want to make safe without breaking its structure.

Whenever a value placed in a URL contains characters outside the unreserved set (letters, digits and - _ . ~) or any character that is reserved for URL structure. Spaces, ampersands, question marks, equals signs, slashes, plus signs and non-ASCII text all need encoding when they appear inside a path segment or query value, otherwise they change how the URL is parsed or break it entirely.

That is correct, expected output. URLs can only contain ASCII, so non-ASCII text is first converted to UTF-8 bytes and each byte is written as a %XX percent-escape. 中文 becomes %E4%B8%AD%E6%96%87. When the URL is decoded, those bytes are reassembled back into the original characters. Decode mode reverses the process and shows you the readable text.

Double encoding happens when an already-encoded string is encoded again, so a space (%20) becomes %2520: the % itself gets encoded to %25. It usually creeps in when a value is encoded at two layers of a system that each assume the other did not. The result is a URL that decodes to gibberish or to a still-encoded string. Decode mode offers a “Decode twice” toggle to peel off both layers, and the tool warns when input looks double-encoded.

Switch to Parse URL mode and paste your URL. The query parameters appear as an editable key/value table; use the add-row button to append a new parameter, type the key and value, and the reassembled URL at the bottom updates live with correct encoding applied. You can also edit or remove existing rows, change the path, host or fragment, then copy the result.

No. Parsing uses the browser’s native URL API on the page itself. There is no server round-trip and nothing is logged. Encoding, decoding and parsing all run locally, so the URLs you work with never leave your device.