curl_easy_unescape - URL decode a string

Added in curl 7.15.4

This function converts the URL encoded string input to a "plain string" and returns that in an allocated memory area. All input characters that are URL encoded (%XX where XX is a two-digit hexadecimal number) are converted to their binary versions. If the length argument is set to 0 (zero), curl_easy_unescape(3) uses strlen() on input to find out the size. If outlength is non-NULL, the function writes the length of the returned string in the integer it points to. This allows proper handling even for strings containing %00. Since this is a pointer to an int type, it can only return a value up to INT_MAX so no longer string can be returned in this parameter. Since 7.82.0, the curl parameter is ignored. Prior to that there was per-handle character conversion support for some old operating systems such as TPF, but it was otherwise ignored. You must curl_free(3) the returned string when you are done with it.

int main(void) { CURL *curl = curl_easy_init(); if(curl) { int decodelen; char *decoded = curl_easy_unescape(curl, "%63%75%72%6c", 12, &decodelen); if(decoded) { /* do not assume printf() works on the decoded data */ printf("Decoded: "); /* ... */ curl_free(decoded); } curl_easy_cleanup(curl); } }

curl_easy_unescape - URL decode a string

This functionality affects all supported protocols

A pointer to a null-terminated string or NULL if it failed.

curl_easy_escape(3), curl_url_get(3) libcurl 2025-06-16 curl_easy_unescape(3)

#include <curl/curl.h> char *curl_easy_unescape(CURL *curl, const char *input, int inlength, int *outlength);