Codificador y Decodificador de URL

URLs were originally designed to transmit ASCII text over the internet. The URL specification (RFC 3986) reserves certain characters for special purposes: '?' separates the path from the query string, '&' separates parameters, '=' separates keys from values, '#' marks a fragment, and '/' separates path segments. When these characters appear in the data portion of a URL (like a search query or a parameter value), they must be encoded to avoid being interpreted as structural delimiters.

URL encoding (percent encoding) replaces each reserved or non-ASCII character with a percent sign (%) followed by two hexadecimal digits representing the character's byte value. For example, a space becomes %20, an ampersand becomes %26, and a forward slash becomes %2F. Characters in the unreserved set (A-Z, a-z, 0-9, hyphen, underscore, period, tilde) are never encoded. The JavaScript function encodeURIComponent() handles this encoding, while decodeURIComponent() reverses it.

Modern URLs also need to handle Unicode characters (emoji, CJK characters, accented letters). These are first encoded as UTF-8 bytes, then each byte is percent-encoded. For example, the coffee emoji 鈽?(U+2615) is encoded as UTF-8 bytes E2 98 95, which becomes %E2%98%95 in a URL. The browser and server automatically handle this encoding when you type a URL or submit a form, but developers often need to manually encode or decode URLs when building API endpoints, redirect URLs, or data URIs.

URL encoding is essential when passing data through URLs in web applications. Common scenarios include: building API query parameters (encoding search terms, filter values), creating redirect URLs that contain the original URL as a parameter (e.g., /login?redirect=%2Fdashboard), generating data URIs for embedded images or fonts, and encoding email links with subject and body parameters (mailto:?subject=...&body=...). OAuth flows also heavily rely on URL encoding for state parameters and callback URLs.

Un error común es la doble codificación — codificar una cadena ya codificada. Por ejemplo, codificar '%20' produciría '%2520' (el signo de porcentaje en sí se codifica a %25). Descodifica siempre antes de volver a codificar si no estás seguro del estado actual de la cadena. Otro problema común es usar encodeURI() en lugar de encodeURIComponent() — encodeURI() no codifica caracteres reservados como ?, & y =. Usa encodeURIComponent() para valores de parámetros individuales y encodeURI() solo para URLs completas.