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::bigquery_analyticshub_v1::AnalyticsHubServiceClient(
google::cloud::bigquery_analyticshub_v1::
MakeAnalyticsHubServiceConnection(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 release candidate version is 2.37.0-rc, with multiple previous versions listed, starting from 2.36.0 down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override default credentials by utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and explicitly loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation includes links to code snippets demonstrating how to override authentication for various \u003ccode\u003e*Client\u003c/code\u003e classes within the BigQuery service.\u003c/p\u003e\n"],["\u003cp\u003eIt is recommended to review the best practices for managing service account keys for more details on secure key management.\u003c/p\u003e\n"]]],[],null,["Version 2.33.0keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/bigquery/latest/bigquery-override-authentication)\n- [2.41.0](/cpp/docs/reference/bigquery/2.41.0/bigquery-override-authentication)\n- [2.40.0](/cpp/docs/reference/bigquery/2.40.0/bigquery-override-authentication)\n- [2.39.0](/cpp/docs/reference/bigquery/2.39.0/bigquery-override-authentication)\n- [2.38.0](/cpp/docs/reference/bigquery/2.38.0/bigquery-override-authentication)\n- [2.37.0](/cpp/docs/reference/bigquery/2.37.0/bigquery-override-authentication)\n- [2.36.0](/cpp/docs/reference/bigquery/2.36.0/bigquery-override-authentication)\n- [2.35.0](/cpp/docs/reference/bigquery/2.35.0/bigquery-override-authentication)\n- [2.34.0](/cpp/docs/reference/bigquery/2.34.0/bigquery-override-authentication)\n- [2.33.0](/cpp/docs/reference/bigquery/2.33.0/bigquery-override-authentication)\n- [2.32.0](/cpp/docs/reference/bigquery/2.32.0/bigquery-override-authentication)\n- [2.31.0](/cpp/docs/reference/bigquery/2.31.0/bigquery-override-authentication)\n- [2.30.0](/cpp/docs/reference/bigquery/2.30.0/bigquery-override-authentication)\n- [2.29.0](/cpp/docs/reference/bigquery/2.29.0/bigquery-override-authentication)\n- [2.28.0](/cpp/docs/reference/bigquery/2.28.0/bigquery-override-authentication)\n- [2.27.0](/cpp/docs/reference/bigquery/2.27.0/bigquery-override-authentication)\n- [2.26.0](/cpp/docs/reference/bigquery/2.26.0/bigquery-override-authentication)\n- [2.25.1](/cpp/docs/reference/bigquery/2.25.1/bigquery-override-authentication)\n- [2.24.0](/cpp/docs/reference/bigquery/2.24.0/bigquery-override-authentication)\n- [2.23.0](/cpp/docs/reference/bigquery/2.23.0/bigquery-override-authentication)\n- [2.22.1](/cpp/docs/reference/bigquery/2.22.1/bigquery-override-authentication)\n- [2.21.0](/cpp/docs/reference/bigquery/2.21.0/bigquery-override-authentication)\n- [2.20.0](/cpp/docs/reference/bigquery/2.20.0/bigquery-override-authentication)\n- [2.19.0](/cpp/docs/reference/bigquery/2.19.0/bigquery-override-authentication)\n- [2.18.0](/cpp/docs/reference/bigquery/2.18.0/bigquery-override-authentication)\n- [2.17.0](/cpp/docs/reference/bigquery/2.17.0/bigquery-override-authentication)\n- [2.16.0](/cpp/docs/reference/bigquery/2.16.0/bigquery-override-authentication)\n- [2.15.1](/cpp/docs/reference/bigquery/2.15.1/bigquery-override-authentication)\n- [2.14.0](/cpp/docs/reference/bigquery/2.14.0/bigquery-override-authentication)\n- [2.13.0](/cpp/docs/reference/bigquery/2.13.0/bigquery-override-authentication)\n- [2.12.0](/cpp/docs/reference/bigquery/2.12.0/bigquery-override-authentication)\n- [2.11.0](/cpp/docs/reference/bigquery/2.11.0/bigquery-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::bigquery_analyticshub_v1::AnalyticsHubServiceClient(\n google::cloud::bigquery_analyticshub_v1::\n MakeAnalyticsHubServiceConnection(options));\n }\n\nFollow these links to find examples for other `*Client` classes:\n\n- [`bigquery_analyticshub_v1::AnalyticsHubServiceClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_analyticshub_v1_1_1AnalyticsHubServiceClient-service-account-snippet)\n- [`bigquery_biglake_v1::MetastoreServiceClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_biglake_v1_1_1MetastoreServiceClient-service-account-snippet)\n- [`bigquery_connection_v1::ConnectionServiceClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_connection_v1_1_1ConnectionServiceClient-service-account-snippet)\n- [`bigquery_datapolicies_v1::DataPolicyServiceClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_datapolicies_v1_1_1DataPolicyServiceClient-service-account-snippet)\n- [`bigquery_datatransfer_v1::DataTransferServiceClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_datatransfer_v1_1_1DataTransferServiceClient-service-account-snippet)\n- [`bigquery_migration_v2::MigrationServiceClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_migration_v2_1_1MigrationServiceClient-service-account-snippet)\n- [`bigquery_reservation_v1::ReservationServiceClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_reservation_v1_1_1ReservationServiceClient-service-account-snippet)\n- [`bigquery_storage_v1::BigQueryReadClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_storage_v1_1_1BigQueryReadClient-service-account-snippet)\n- [`bigquery_storage_v1::BigQueryWriteClient`](/cpp/docs/reference/bigquery/2.33.0/bigquery_storage_v1_1_1BigQueryWriteClient-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."]]