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::billing_budgets_v1::BudgetServiceClient(
google::cloud::billing_budgets_v1::MakeBudgetServiceConnection(
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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 provides documentation for overriding default authentication credentials when using Google Cloud client libraries, specifically focusing on how to load a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version is 2.37.0-rc, and this page also lists documentation for older versions, down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eThe \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e allows developers to override default authentication using a service account key file, which can be implemented as illustrated by a code example for loading a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples for other client classes such as \u003ccode\u003ebilling_budgets_v1::BudgetServiceClient\u003c/code\u003e, \u003ccode\u003ebilling_v1::CloudBillingClient\u003c/code\u003e, and \u003ccode\u003ebilling_v1::CloudCatalogClient\u003c/code\u003e are also available.\u003c/p\u003e\n"],["\u003cp\u003eRefer to the "Best practices for managing service account keys" guide and the "Authentication Components" documentation for more in-depth details on managing service account keys and creating credentials objects.\u003c/p\u003e\n"]]],[],null,[]]
