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 client libraries, primarily in the context of BigQuery services.\u003c/p\u003e\n"],["\u003cp\u003eBy default, Google Cloud client libraries use Application Default Credentials, but this can be overridden using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe page showcases an example of how to load credentials explicitly using a service account key file, demonstrating a basic implementation of this process.\u003c/p\u003e\n"],["\u003cp\u003eLinks to examples for overriding credentials for various \u003ccode\u003e*Client\u003c/code\u003e classes within the BigQuery family of services are provided, such as \u003ccode\u003eAnalyticsHubServiceClient\u003c/code\u003e, \u003ccode\u003eMetastoreServiceClient\u003c/code\u003e, and \u003ccode\u003eBigQueryReadClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe content presented goes from version 2.37.0-rc (latest), down to 2.11.0, and users can refer to a guide on managing service account keys for more information.\u003c/p\u003e\n"]]],[],null,["Version 2.28.0keyboard_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/2.28.0/bigquery_analyticshub_v1_1_1AnalyticsHubServiceClient-service-account-snippet)\n- [`bigquery_biglake_v1::MetastoreServiceClient`](/cpp/docs/reference/bigquery/2.28.0/bigquery_biglake_v1_1_1MetastoreServiceClient-service-account-snippet)\n- [`bigquery_connection_v1::ConnectionServiceClient`](/cpp/docs/reference/bigquery/2.28.0/bigquery_connection_v1_1_1ConnectionServiceClient-service-account-snippet)\n- [`bigquery_datapolicies_v1::DataPolicyServiceClient`](/cpp/docs/reference/bigquery/2.28.0/bigquery_datapolicies_v1_1_1DataPolicyServiceClient-service-account-snippet)\n- [`bigquery_datatransfer_v1::DataTransferServiceClient`](/cpp/docs/reference/bigquery/2.28.0/bigquery_datatransfer_v1_1_1DataTransferServiceClient-service-account-snippet)\n- [`bigquery_migration_v2::MigrationServiceClient`](/cpp/docs/reference/bigquery/2.28.0/bigquery_migration_v2_1_1MigrationServiceClient-service-account-snippet)\n- [`bigquery_reservation_v1::ReservationServiceClient`](/cpp/docs/reference/bigquery/2.28.0/bigquery_reservation_v1_1_1ReservationServiceClient-service-account-snippet)\n- [`bigquery_storage_v1::BigQueryReadClient`](/cpp/docs/reference/bigquery/2.28.0/bigquery_storage_v1_1_1BigQueryReadClient-service-account-snippet)\n- [`bigquery_storage_v1::BigQueryWriteClient`](/cpp/docs/reference/bigquery/2.28.0/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."]]