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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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\u003eTo override the default credentials, you can use \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and explicitly load a service account key file, as demonstrated in the provided code example.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version of these documents are the 2.37.0-rc release candidate, which are listed on this page, as well as all releases back to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eExamples of overriding authentication for \u003ccode\u003efunctions_v1::CloudFunctionsServiceClient\u003c/code\u003e and \u003ccode\u003efunctions_v2::FunctionServiceClient\u003c/code\u003e are available via provided links.\u003c/p\u003e\n"],["\u003cp\u003eRefer to the "Best practices for managing service account keys" guide for detailed information on managing service account keys and the "Authentication Components" page for more information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
