Unless otherwise configured, the client libraries useApplication Default Credentialsto 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 theUnifiedCredentialsOptionThe 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::monitoring_dashboard_v1::DashboardsServiceClient(
google::cloud::monitoring_dashboard_v1::MakeDashboardsServiceConnection(
options));
}
Follow these links to find examples for other*Clientclasses:
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-09-04 UTC."],[[["\u003cp\u003eThis page provides documentation for overriding default authentication credentials when using Google Cloud C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version documentation is for 2.37.0-rc, but the page also contains version history going all the way back to 2.11.0, including all the versions in between.\u003c/p\u003e\n"],["\u003cp\u003eBy default, C++ client libraries use Application Default Credentials for Google Cloud Services, but these can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eYou can override default credentials by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, and the example demonstrates loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eLinks to examples for multiple \u003ccode\u003e*Client\u003c/code\u003e classes, such as \u003ccode\u003eDashboardsServiceClient\u003c/code\u003e, \u003ccode\u003eMetricsScopesClient\u003c/code\u003e, and \u003ccode\u003eAlertPolicyServiceClient\u003c/code\u003e are available, along with a link to the best practices for managing service accounts.\u003c/p\u003e\n"]]],[],null,["Version 2.18.0keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/monitoring/latest/monitoring-override-authentication)\n- [2.41.0](/cpp/docs/reference/monitoring/2.41.0/monitoring-override-authentication)\n- [2.40.0](/cpp/docs/reference/monitoring/2.40.0/monitoring-override-authentication)\n- [2.39.0](/cpp/docs/reference/monitoring/2.39.0/monitoring-override-authentication)\n- [2.38.0](/cpp/docs/reference/monitoring/2.38.0/monitoring-override-authentication)\n- [2.37.0](/cpp/docs/reference/monitoring/2.37.0/monitoring-override-authentication)\n- [2.36.0](/cpp/docs/reference/monitoring/2.36.0/monitoring-override-authentication)\n- [2.35.0](/cpp/docs/reference/monitoring/2.35.0/monitoring-override-authentication)\n- [2.34.0](/cpp/docs/reference/monitoring/2.34.0/monitoring-override-authentication)\n- [2.33.0](/cpp/docs/reference/monitoring/2.33.0/monitoring-override-authentication)\n- [2.32.0](/cpp/docs/reference/monitoring/2.32.0/monitoring-override-authentication)\n- [2.31.0](/cpp/docs/reference/monitoring/2.31.0/monitoring-override-authentication)\n- [2.30.0](/cpp/docs/reference/monitoring/2.30.0/monitoring-override-authentication)\n- [2.29.0](/cpp/docs/reference/monitoring/2.29.0/monitoring-override-authentication)\n- [2.28.0](/cpp/docs/reference/monitoring/2.28.0/monitoring-override-authentication)\n- [2.27.0](/cpp/docs/reference/monitoring/2.27.0/monitoring-override-authentication)\n- [2.26.0](/cpp/docs/reference/monitoring/2.26.0/monitoring-override-authentication)\n- [2.25.1](/cpp/docs/reference/monitoring/2.25.1/monitoring-override-authentication)\n- [2.24.0](/cpp/docs/reference/monitoring/2.24.0/monitoring-override-authentication)\n- [2.23.0](/cpp/docs/reference/monitoring/2.23.0/monitoring-override-authentication)\n- [2.22.1](/cpp/docs/reference/monitoring/2.22.1/monitoring-override-authentication)\n- [2.21.0](/cpp/docs/reference/monitoring/2.21.0/monitoring-override-authentication)\n- [2.20.0](/cpp/docs/reference/monitoring/2.20.0/monitoring-override-authentication)\n- [2.19.0](/cpp/docs/reference/monitoring/2.19.0/monitoring-override-authentication)\n- [2.18.0](/cpp/docs/reference/monitoring/2.18.0/monitoring-override-authentication)\n- [2.17.0](/cpp/docs/reference/monitoring/2.17.0/monitoring-override-authentication)\n- [2.16.0](/cpp/docs/reference/monitoring/2.16.0/monitoring-override-authentication)\n- [2.15.1](/cpp/docs/reference/monitoring/2.15.1/monitoring-override-authentication)\n- [2.14.0](/cpp/docs/reference/monitoring/2.14.0/monitoring-override-authentication)\n- [2.13.0](/cpp/docs/reference/monitoring/2.13.0/monitoring-override-authentication)\n- [2.12.0](/cpp/docs/reference/monitoring/2.12.0/monitoring-override-authentication)\n- [2.11.0](/cpp/docs/reference/monitoring/2.11.0/monitoring-override-authentication) \n\nHow to Override the Authentication Credentials\n==============================================\n\nUnless otherwise configured, the client libraries use [Application Default Credentials](https://cloud.google.com/docs/authentication#adc) 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](https://cloud.google.com/cpp/docs/reference/common/latest/structgoogle_1_1cloud_1_1UnifiedCredentialsOption.html) The following example shows how to explicitly load a service account key file: \n\n [](std::string const& keyfile) {\n auto is = std::ifstream(keyfile);\n is.exceptions(std::ios::badbit); // Minimal error handling in examples\n auto contents = std::string(std::istreambuf_iterator\u003cchar\u003e(is.rdbuf()), {});\n auto options =\n google::cloud::Options{}.set\u003cgoogle::cloud::UnifiedCredentialsOption\u003e(\n google::cloud::MakeServiceAccountCredentials(contents));\n return google::cloud::monitoring_dashboard_v1::DashboardsServiceClient(\n google::cloud::monitoring_dashboard_v1::MakeDashboardsServiceConnection(\n options));\n }\n\nFollow these links to find examples for other `*Client` classes:\n\n- [`monitoring_dashboard_v1::DashboardsServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_dashboard_v1_1_1DashboardsServiceClient-service-account-snippet)\n- [`monitoring_metricsscope_v1::MetricsScopesClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_metricsscope_v1_1_1MetricsScopesClient-service-account-snippet)\n- [`monitoring_v3::AlertPolicyServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1AlertPolicyServiceClient-service-account-snippet)\n- [`monitoring_v3::GroupServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1GroupServiceClient-service-account-snippet)\n- [`monitoring_v3::MetricServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1MetricServiceClient-service-account-snippet)\n- [`monitoring_v3::NotificationChannelServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1NotificationChannelServiceClient-service-account-snippet)\n- [`monitoring_v3::QueryServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1QueryServiceClient-service-account-snippet)\n- [`monitoring_v3::ServiceMonitoringServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1ServiceMonitoringServiceClient-service-account-snippet)\n- [`monitoring_v3::SnoozeServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1SnoozeServiceClient-service-account-snippet)\n- [`monitoring_v3::UptimeCheckServiceClient`](/cpp/docs/reference/monitoring/2.18.0/monitoring_v3_1_1UptimeCheckServiceClient-service-account-snippet)\n\nKeep in mind that we chose this as an example because it is relatively easy to understand. Consult the [Best practices for managing service account keys](https://cloud.google.com/iam/docs/best-practices-for-managing-service-account-keys) guide for more details.\n\n###### See Also\n\n[Authentication Components](https://cloud.google.com/cpp/docs/reference/common/latest/group__guac.html) - for more information on the factory functions to create [`google::cloud::Credentials`](https://cloud.google.com/cpp/docs/reference/common/latest/classgoogle_1_1cloud_1_1Credentials.html) objects."]]