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::run_v2::ExecutionsClient(
google::cloud::run_v2::MakeExecutionsConnection(options));
}
Follow these links to find examples for other *Client classes:
[[["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 document details how to override the default Application Default Credentials (ADC) for authenticating with Google Cloud Services using C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e allows explicit loading of a service account key file for authentication, overriding the default credentials.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version documented is 2.37.0-rc, but the page also provides access to previous versions of documentation dating back to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for overriding authentication within \u003ccode\u003erun_v2::ExecutionsClient\u003c/code\u003e, \u003ccode\u003erun_v2::JobsClient\u003c/code\u003e, \u003ccode\u003erun_v2::RevisionsClient\u003c/code\u003e, \u003ccode\u003erun_v2::ServicesClient\u003c/code\u003e, and \u003ccode\u003erun_v2::TasksClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eFor enhanced security and management, users should refer to the "Best practices for managing service account keys" guide, as it is only shown as an example.\u003c/p\u003e\n"]]],[],null,["Version latestkeyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/run/latest/run-override-authentication)\n- [2.41.0](/cpp/docs/reference/run/2.41.0/run-override-authentication)\n- [2.40.0](/cpp/docs/reference/run/2.40.0/run-override-authentication)\n- [2.39.0](/cpp/docs/reference/run/2.39.0/run-override-authentication)\n- [2.38.0](/cpp/docs/reference/run/2.38.0/run-override-authentication)\n- [2.37.0](/cpp/docs/reference/run/2.37.0/run-override-authentication)\n- [2.36.0](/cpp/docs/reference/run/2.36.0/run-override-authentication)\n- [2.35.0](/cpp/docs/reference/run/2.35.0/run-override-authentication)\n- [2.34.0](/cpp/docs/reference/run/2.34.0/run-override-authentication)\n- [2.33.0](/cpp/docs/reference/run/2.33.0/run-override-authentication)\n- [2.32.0](/cpp/docs/reference/run/2.32.0/run-override-authentication)\n- [2.31.0](/cpp/docs/reference/run/2.31.0/run-override-authentication)\n- [2.30.0](/cpp/docs/reference/run/2.30.0/run-override-authentication)\n- [2.29.0](/cpp/docs/reference/run/2.29.0/run-override-authentication)\n- [2.28.0](/cpp/docs/reference/run/2.28.0/run-override-authentication)\n- [2.27.0](/cpp/docs/reference/run/2.27.0/run-override-authentication)\n- [2.26.0](/cpp/docs/reference/run/2.26.0/run-override-authentication)\n- [2.25.1](/cpp/docs/reference/run/2.25.1/run-override-authentication)\n- [2.24.0](/cpp/docs/reference/run/2.24.0/run-override-authentication)\n- [2.23.0](/cpp/docs/reference/run/2.23.0/run-override-authentication)\n- [2.22.1](/cpp/docs/reference/run/2.22.1/run-override-authentication)\n- [2.21.0](/cpp/docs/reference/run/2.21.0/run-override-authentication)\n- [2.20.0](/cpp/docs/reference/run/2.20.0/run-override-authentication)\n- [2.19.0](/cpp/docs/reference/run/2.19.0/run-override-authentication)\n- [2.18.0](/cpp/docs/reference/run/2.18.0/run-override-authentication)\n- [2.17.0](/cpp/docs/reference/run/2.17.0/run-override-authentication)\n- [2.16.0](/cpp/docs/reference/run/2.16.0/run-override-authentication)\n- [2.15.1](/cpp/docs/reference/run/2.15.1/run-override-authentication)\n- [2.14.0](/cpp/docs/reference/run/2.14.0/run-override-authentication)\n- [2.13.0](/cpp/docs/reference/run/2.13.0/run-override-authentication)\n- [2.12.0](/cpp/docs/reference/run/2.12.0/run-override-authentication)\n- [2.11.0](/cpp/docs/reference/run/2.11.0/run-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::run_v2::ExecutionsClient(\n google::cloud::run_v2::MakeExecutionsConnection(options));\n }\n\nFollow these links to find examples for other `*Client` classes:\n\n- [`run_v2::ExecutionsClient`](/cpp/docs/reference/run/latest/run_v2_1_1ExecutionsClient-service-account-snippet)\n- [`run_v2::JobsClient`](/cpp/docs/reference/run/latest/run_v2_1_1JobsClient-service-account-snippet)\n- [`run_v2::RevisionsClient`](/cpp/docs/reference/run/latest/run_v2_1_1RevisionsClient-service-account-snippet)\n- [`run_v2::ServicesClient`](/cpp/docs/reference/run/latest/run_v2_1_1ServicesClient-service-account-snippet)\n- [`run_v2::TasksClient`](/cpp/docs/reference/run/latest/run_v2_1_1TasksClient-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."]]