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::ids_v1::IDSClient(
google::cloud::ids_v1::MakeIDSConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 page provides documentation for overriding default authentication credentials in the Google Cloud C++ client library for various versions, from 2.11.0 to the latest release candidate 2.37.0-rc.\u003c/p\u003e\n"],["\u003cp\u003eThe C++ client libraries typically use Application Default Credentials (ADC) for authentication, but you can override this behavior when needed.\u003c/p\u003e\n"],["\u003cp\u003eOverriding involves providing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated in the provided code example using a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example shows how to load credentials from a service account key file, but it is simplified for clarity, and users should refer to the "Best practices for managing service account keys" guide for more comprehensive information.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation offers links to "Authentication Components" for further information on creating \u003ca href=\"https://cloud.google.com/cpp/docs/reference/common/latest/classgoogle_1_1cloud_1_1Credentials.html\"\u003e\u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e\u003c/a\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
