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::channel_v1::CloudChannelServiceClient(
google::cloud::channel_v1::MakeCloudChannelServiceConnection(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, specifically focusing on the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release is version 2.37.0-rc, with links available for versions back to 2.11.0, providing reference documentation for each.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override the default Application Default Credentials by providing a service account key file to authenticate with Google Cloud Services, as shown in the example provided.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for both \u003ccode\u003echannel_v1::CloudChannelServiceClient\u003c/code\u003e and \u003ccode\u003echannel_v1::CloudChannelReportsServiceClient\u003c/code\u003e classes, illustrating how to implement service account authentication.\u003c/p\u003e\n"],["\u003cp\u003eBest practices for managing service account keys can be found in the linked guide, and more information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects is available in the Authentication Components section.\u003c/p\u003e\n"]]],[],null,["Version 2.33.0keyboard_arrow_down\n\n- [2.42.0-rc (latest)](/cpp/docs/reference/channel/latest/channel-override-authentication)\n- [2.41.0](/cpp/docs/reference/channel/2.41.0/channel-override-authentication)\n- [2.40.0](/cpp/docs/reference/channel/2.40.0/channel-override-authentication)\n- [2.39.0](/cpp/docs/reference/channel/2.39.0/channel-override-authentication)\n- [2.38.0](/cpp/docs/reference/channel/2.38.0/channel-override-authentication)\n- [2.37.0](/cpp/docs/reference/channel/2.37.0/channel-override-authentication)\n- [2.36.0](/cpp/docs/reference/channel/2.36.0/channel-override-authentication)\n- [2.35.0](/cpp/docs/reference/channel/2.35.0/channel-override-authentication)\n- [2.34.0](/cpp/docs/reference/channel/2.34.0/channel-override-authentication)\n- [2.33.0](/cpp/docs/reference/channel/2.33.0/channel-override-authentication)\n- [2.32.0](/cpp/docs/reference/channel/2.32.0/channel-override-authentication)\n- [2.31.0](/cpp/docs/reference/channel/2.31.0/channel-override-authentication)\n- [2.30.0](/cpp/docs/reference/channel/2.30.0/channel-override-authentication)\n- [2.29.0](/cpp/docs/reference/channel/2.29.0/channel-override-authentication)\n- [2.28.0](/cpp/docs/reference/channel/2.28.0/channel-override-authentication)\n- [2.27.0](/cpp/docs/reference/channel/2.27.0/channel-override-authentication)\n- [2.26.0](/cpp/docs/reference/channel/2.26.0/channel-override-authentication)\n- [2.25.1](/cpp/docs/reference/channel/2.25.1/channel-override-authentication)\n- [2.24.0](/cpp/docs/reference/channel/2.24.0/channel-override-authentication)\n- [2.23.0](/cpp/docs/reference/channel/2.23.0/channel-override-authentication)\n- [2.22.1](/cpp/docs/reference/channel/2.22.1/channel-override-authentication)\n- [2.21.0](/cpp/docs/reference/channel/2.21.0/channel-override-authentication)\n- [2.20.0](/cpp/docs/reference/channel/2.20.0/channel-override-authentication)\n- [2.19.0](/cpp/docs/reference/channel/2.19.0/channel-override-authentication)\n- [2.18.0](/cpp/docs/reference/channel/2.18.0/channel-override-authentication)\n- [2.17.0](/cpp/docs/reference/channel/2.17.0/channel-override-authentication)\n- [2.16.0](/cpp/docs/reference/channel/2.16.0/channel-override-authentication)\n- [2.15.1](/cpp/docs/reference/channel/2.15.1/channel-override-authentication)\n- [2.14.0](/cpp/docs/reference/channel/2.14.0/channel-override-authentication)\n- [2.13.0](/cpp/docs/reference/channel/2.13.0/channel-override-authentication)\n- [2.12.0](/cpp/docs/reference/channel/2.12.0/channel-override-authentication)\n- [2.11.0](/cpp/docs/reference/channel/2.11.0/channel-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::channel_v1::CloudChannelServiceClient(\n google::cloud::channel_v1::MakeCloudChannelServiceConnection(options));\n }\n\nFollow these links to find examples for other `*Client` classes:\n\n- [`channel_v1::CloudChannelServiceClient`](/cpp/docs/reference/channel/2.33.0/channel_v1_1_1CloudChannelServiceClient-service-account-snippet)\n- [`channel_v1::CloudChannelReportsServiceClient`](/cpp/docs/reference/channel/2.33.0/channel_v1_1_1CloudChannelReportsServiceClient-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."]]