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::SpeechClient(
google::cloud::speech_v1::MakeSpeechConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 authentication credentials used by the client libraries when interacting with Google Cloud Services, which typically rely on Application Default Credentials.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default credentials by using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as demonstrated in the provided example that shows how to explicitly load a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples for overriding authentication are available for both \u003ccode\u003espeech_v1::SpeechClient\u003c/code\u003e and \u003ccode\u003espeech_v2::SpeechClient\u003c/code\u003e classes, linked within the documentation.\u003c/p\u003e\n"],["\u003cp\u003eThe example provided is easy to understand, but for best practices on service account key management, refer to the linked guide on managing service account keys.\u003c/p\u003e\n"],["\u003cp\u003eMore information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects can be found in the linked "Authentication Components" section.\u003c/p\u003e\n"]]],[],null,[]]
