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::speech_v1::AdaptationClient(
google::cloud::speech_v1::MakeAdaptationConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 information on how to override the default authentication credentials used by Google Cloud client libraries, which typically use Application Default Credentials.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default credentials by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to load specific credentials, such as a service account key file, as shown in the provided code example.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available in this documentation is 2.37.0-rc, and it outlines the history of different versions going down to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for overriding credentials for \u003ccode\u003espeech_v1::AdaptationClient\u003c/code\u003e, \u003ccode\u003espeech_v1::SpeechClient\u003c/code\u003e, and \u003ccode\u003espeech_v2::SpeechClient\u003c/code\u003e classes, and the documentation advises to check the best practices guide for service account key management.\u003c/p\u003e\n"],["\u003cp\u003eThe "See Also" section directs users to the Authentication Components documentation for more details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
