05 // Unicode, Symbol & Encoding WorkbenchURL-CODEC
URL Percent-Encoder & Decoder (`encodeURIComponent` Workbench)
RFC 3986 percent-encoding converts reserved URI delimiters and multi-byte UTF-8 octets into `%XX` hexadecimal triplets so query strings parse unambiguously.
Encoded Output
https%3A%2F%2Ffinaltoolbox.com%2Fcalculators%3Fformula%3DE%3Dmc%C2%B2%26query%3Dphysics%2Bconstants
Decoded Output
https://finaltoolbox.com/calculators?formula=E=mc²&query=physics constants
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Reference Table
- 01Use `encodeURIComponent` for individual query parameter keys/values (encodes `&`, `=`, `+`, `/`, `?`, `#`), and `encodeURI` only for full URLs where structural slashes and `?` must stay intact.
Frequently Asked Questions
Why do spaces sometimes appear as `+` instead of `%20`?+
`application/x-www-form-urlencoded` (HTML form queries) encodes spaces as `+` (and literal `+` as `%2B`), whereas pure RFC 3986 URI path/component encoding uses `%20`.
Which characters are never escaped by `encodeURIComponent`?+
Unreserved RFC 3986 characters `A–Z`, `a–z`, `0–9`, `-`, `_`, `.`, `!`, `~`, `*`, `'`, `(`, `)`.
What causes `URIError: URI malformed` during decoding?+
A stray `%` not followed by two hex digits, or an incomplete UTF-8 byte sequence such as `%E2%88` missing its third continuation byte.