Unless otherwise configured, the client libraries use Application Default Credentials to authenticate with Google Cloud Services. While this works for most applications, in some cases you may need to override this default. You can do so by providing the UnifiedCredentialsOption The following example shows how to explicitly load a service account key file:
[](std::string const& keyfile) {
auto is = std::ifstream(keyfile);
is.exceptions(std::ios::badbit); // Minimal error handling in examples
auto contents = std::string(std::istreambuf_iterator<char>(is.rdbuf()), {});
auto options =
google::cloud::Options{}.set<google::cloud::UnifiedCredentialsOption>(
google::cloud::MakeServiceAccountCredentials(contents));
return google::cloud::apikeys_v2::ApiKeysClient(
google::cloud::apikeys_v2::MakeApiKeysConnection(options));
}
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis webpage provides documentation for overriding default authentication credentials when using Google Cloud client libraries, specifically focusing on API keys and C++.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version of the documentation available is 2.37.0-rc, while the current displayed version is 2.29.0, with a history of versions listed from 2.36.0 down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eThe preferred method to override the default authentication is to utilize the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and provides an example of how to load a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eDefault authentication uses Application Default Credentials, but the documentation provides instructions on how to override this.\u003c/p\u003e\n"],["\u003cp\u003eFor further information, users are encouraged to view the guide on best practices for managing service account keys and authentication components.\u003c/p\u003e\n"]]],[],null,[]]
