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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eThis page provides documentation for overriding default authentication credentials in C++ client libraries when interacting with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available is 2.37.0-rc, and the page contains documentation for various versions, from 2.37.0-rc down to 2.11.0, each with its specific documentation page.\u003c/p\u003e\n"],["\u003cp\u003eBy utilizing \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, developers can explicitly load service account key files to customize the authentication process.\u003c/p\u003e\n"],["\u003cp\u003eThe example demonstrates how to load a service account key file via a basic code snippet using \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e and \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to override the default credentials.\u003c/p\u003e\n"],["\u003cp\u003eFor a more in-depth explanation on creating \u003ccode\u003eCredentials\u003c/code\u003e objects, refer to the Authentication Components documentation.\u003c/p\u003e\n"]]],[],null,[]]
