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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 C++ client libraries when interacting with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version documented is 2.37.0-rc, with a range of versions from 2.11.0 to 2.36.0 also available for reference.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, such as by loading a service account key file as shown in the example code snippet.\u003c/p\u003e\n"],["\u003cp\u003eThe documentation provides links to examples for \u003ccode\u003elanguage_v1::LanguageServiceClient\u003c/code\u003e and \u003ccode\u003elanguage_v2::LanguageServiceClient\u003c/code\u003e classes.\u003c/p\u003e\n"],["\u003cp\u003eFor managing service account keys and creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects consult the referenced best practices guide and authentication components documentation.\u003c/p\u003e\n"]]],[],null,[]]
