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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 version-specific details for overriding default authentication credentials when using Google Cloud Speech client libraries in C++.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version available is 2.37.0-rc, and the documentation includes details from version 2.36.0 down to 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eClient libraries typically use Application Default Credentials, but the provided code snippet and instructions illustrate how to override this by loading a service account key file with the UnifiedCredentialsOption.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for \u003ccode\u003espeech_v1::AdaptationClient\u003c/code\u003e, \u003ccode\u003espeech_v1::SpeechClient\u003c/code\u003e, and \u003ccode\u003espeech_v2::SpeechClient\u003c/code\u003e to show how to manage service accounts.\u003c/p\u003e\n"],["\u003cp\u003eThere are also further links available to explain the \u003ca href=\"https://cloud.google.com/cpp/docs/reference/common/latest/group__guac.html\"\u003eAuthentication Components\u003c/a\u003e and the \u003ca href=\"https://cloud.google.com/iam/docs/best-practices-for-managing-service-account-keys\"\u003eBest practices for managing service account keys\u003c/a\u003e.\u003c/p\u003e\n"]]],[],null,[]]
