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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 page documents how to override the default Application Default Credentials (ADC) for authenticating with Google Cloud Services.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version, 2.37.0-rc, and multiple previous versions, including the current version, 2.14.0, of the documentation are available for reference.\u003c/p\u003e\n"],["\u003cp\u003eYou can override authentication by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e to load a service account key file, as shown in the provided example.\u003c/p\u003e\n"],["\u003cp\u003eExamples are available for \u003ccode\u003espeech_v1::AdaptationClient\u003c/code\u003e, \u003ccode\u003espeech_v1::SpeechClient\u003c/code\u003e, and \u003ccode\u003espeech_v2::SpeechClient\u003c/code\u003e, demonstrating how to override authentication for each.\u003c/p\u003e\n"],["\u003cp\u003eThe page links to best practices for managing service account keys and provides additional information on authentication components.\u003c/p\u003e\n"]]],[],null,[]]
