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::functions_v1::CloudFunctionsServiceClient(
google::cloud::functions_v1::MakeCloudFunctionsServiceConnection(
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"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis page documents how to override the default authentication credentials used by Google Cloud client libraries, which typically rely on Application Default Credentials.\u003c/p\u003e\n"],["\u003cp\u003eYou can override default credentials by utilizing the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and providing explicit credentials, such as those from a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe provided example demonstrates loading credentials from a service account key file using \u003ccode\u003eMakeServiceAccountCredentials\u003c/code\u003e within a C++ context.\u003c/p\u003e\n"],["\u003cp\u003eExamples for \u003ccode\u003eCloudFunctionsServiceClient\u003c/code\u003e and \u003ccode\u003eFunctionServiceClient\u003c/code\u003e are linked, offering specific guidance for those client classes in versions 2.31.0 of the reference documentation.\u003c/p\u003e\n"],["\u003cp\u003eThe page references best practices for managing service account keys and the Authentication Components for more details on credential management within Google Cloud.\u003c/p\u003e\n"]]],[],null,[]]
