Convert DOC Files to DOCX in C/C++

1 min readApr 9, 2021


Using outdated file formats can cause compatibility and formatting issues when it comes to sharing them with sources who have upgraded to the current formats. In the following tutorial, we will demonstrate how you can avoid these issues by using an API on the older Word DOC format to instantly convert it to the modern DOCX format.

The first step is to install libcurl into your C/C++ project:


After the installation, we are ready to call the conversion function:

CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "POST");
curl_easy_setopt(curl, CURLOPT_URL, "");
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
curl_easy_setopt(curl, CURLOPT_DEFAULT_PROTOCOL, "https");
struct curl_slist *headers = NULL;
headers = curl_slist_append(headers, "Content-Type: multipart/form-data");
headers = curl_slist_append(headers, "Apikey: YOUR-API-KEY-HERE");
curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);
curl_mime *mime;
curl_mimepart *part;
mime = curl_mime_init(curl);
part = curl_mime_addpart(mime);
curl_mime_name(part, "inputFile");
curl_mime_filedata(part, "/path/to/file");
curl_easy_setopt(curl, CURLOPT_MIMEPOST, mime);
res = curl_easy_perform(curl);

Done! If you have any questions about the API, or need to retrieve your free API key, simply visit the Cloudmersive website.




There’s an API for that. Cloudmersive is a leader in Highly Scalable Cloud APIs.