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::tasks_v2::CloudTasksClient(
google::cloud::tasks_v2::MakeCloudTasksConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThe latest version available is 2.37.0-rc, with numerous other versions from 2.36.0 down to 2.11.0 also being accessible.\u003c/p\u003e\n"],["\u003cp\u003eThe content explains how to override default authentication credentials, which typically rely on Application Default Credentials, using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eYou can load a service account key file explicitly by creating a \u003ccode\u003egoogle::cloud::Options\u003c/code\u003e object and setting the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e with the service account key file contents using \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe example code demonstrates how to load a service account key file and use it for authentication, and it is suggested that you should reference the "Best practices for managing service account keys" guide for more details.\u003c/p\u003e\n"],["\u003cp\u003eThe document "Authentication Components" is provided for additional information about creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
