curl_easy_escape - URL encode a string

Added in curl 7.15.4

This function converts the given input string to a URL encoded string and returns that as a new allocated string. All input characters that are not a-z, A-Z, 0-9, '-', '.', '_' or '~' are converted to their "URL escaped" version (%NN where NN is a two-digit hexadecimal number). If length is set to 0 (zero), curl_easy_escape(3) uses strlen() on the input string to find out the size. This function does not accept input strings longer than CURL_MAX_INPUT_LENGTH (8 MB). You must curl_free(3) the returned string when you are done with it.

libcurl is typically not aware of, nor does it care about, character encodings. curl_easy_escape(3) encodes the data byte-by-byte into the URL encoded version without knowledge or care for what particular character encoding the application or the receiving server may assume that the data uses. The caller of curl_easy_escape(3) must make sure that the data passed in to the function is encoded correctly.

int main(void) { CURL *curl = curl_easy_init(); if(curl) { char *output = curl_easy_escape(curl, "data to convert", 15); if(output) { printf("Encoded: %s\n", output); curl_free(output); } curl_easy_cleanup(curl); } }

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.

curl_easy_escape - URL encode a string

This functionality affects all supported protocols

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

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

#include <curl/curl.h> char *curl_easy_escape(CURL *curl, const char *string, int length);

URLs are by definition URLencoded. To create a proper URL from a set of components that may not be URL encoded already, you cannot just URL encode the entire URL string with curl_easy_escape(3), because it then also converts colons, slashes and other symbols that you probably want untouched. To create a proper URL from strings that are not already URL encoded, we recommend using libcurl's URL API: set the pieces with curl_url_set(3) and get the final correct URL with curl_url_get(3).