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::language_v1::LanguageServiceClient(
google::cloud::language_v1::MakeLanguageServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 in Google Cloud C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version documented is 2.37.0-rc, with a history of versions going back to 2.11.0, all of which can be accessed through individual links.\u003c/p\u003e\n"],["\u003cp\u003eUsers can override default authentication by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and loading a service account key file, as demonstrated in the example provided.\u003c/p\u003e\n"],["\u003cp\u003eExamples are available for both \u003ccode\u003elanguage_v1::LanguageServiceClient\u003c/code\u003e and \u003ccode\u003elanguage_v2::LanguageServiceClient\u003c/code\u003e, for how to override these in practice.\u003c/p\u003e\n"],["\u003cp\u003eFor more information and best practices, refer to the documentation on managing service account keys and authentication components.\u003c/p\u003e\n"]]],[],null,[]]
