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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 links provided for documentation and details on overriding authentication for this version and many previous ones.\u003c/p\u003e\n"],["\u003cp\u003eThe content focuses on how to override default authentication credentials, which are typically Application Default Credentials, when interacting with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eYou can override default authentication by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and explicitly loading a service account key file, as demonstrated in the code example.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices on managing service account keys, refer to the provided link in the documentation.\u003c/p\u003e\n"],["\u003cp\u003eMore details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the "Authentication Components" section, which is linked in the "See Also" part.\u003c/p\u003e\n"]]],[],null,[]]
