URL Encoder & Decoder

URLs can only safely contain a limited set of characters. Anything else — spaces, &, ?, #, and other reserved or unsafe characters — has to be escaped into a %XX form (its byte value in hex) so it can't be misread as part of the URL's own structure. A space becomes %20, & becomes %26, and so on. Without this, a value like "Q&A" inside a query parameter would be misread as two separate parameters instead of one value containing an ampersand.

This is the most common source of bugs with this kind of tool. encodeURIComponent escapes everything, including characters like &, ?, and / that are meaningful in a URL's structure — use it for a single VALUE, like one query parameter. encodeURI leaves those structural characters alone, because it expects a complete URL, not a fragment of one. For example, encoding "a=1&b=2" with encodeURIComponent gives "a%3D1%26b%3D2" (correct for putting that whole string inside one query value) — but running the same text through encodeURI leaves it as "a=1&b=2" unchanged, because =, &, and the rest are valid, structural characters in a full URL. Both are correct — they're just answering different questions: this tool's "Component" mode is encodeURIComponent, and "Full URL" mode is encodeURI.

Percent-encoding requires each "%" to be followed by exactly two valid hex digits. A stray "%" from messy pasted data — one that isn't followed by two hex digits, like a lone "%" or "%ZZ" — can't be decoded, and the browser's native decode functions throw an error rather than guessing. This tool catches that and points at roughly where the invalid sequence is, instead of failing silently or crashing.

No. All encoding, decoding, and parsing happens locally in your browser using native Web APIs. Nothing is uploaded, logged, or transmitted.