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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 document provides a reference for various versions of the C++ client library, ranging from version 2.11.0 up to the latest release candidate, 2.37.0-rc, including the version that this page corresponds to, 2.28.0.\u003c/p\u003e\n"],["\u003cp\u003eThe client libraries typically authenticate with Google Cloud Services using Application Default Credentials, but they allow you to override this behavior using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eA code snippet demonstrates how to load a service account key file and use it for authentication, including instructions to manage service account keys following best practices.\u003c/p\u003e\n"],["\u003cp\u003eExamples for other \u003ccode\u003e*Client\u003c/code\u003e classes, such as \u003ccode\u003elanguage_v1::LanguageServiceClient\u003c/code\u003e and \u003ccode\u003elanguage_v2::LanguageServiceClient\u003c/code\u003e, are provided for easy reference and implementation of the authentication process.\u003c/p\u003e\n"],["\u003cp\u003eThe document directs users to additional resources, specifically the Authentication Components, for more information on the factory functions for creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
