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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 details how to override the default Application Default Credentials (ADC) for authenticating with Google Cloud Services using the \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eYou can override authentication by explicitly loading a service account key file, as demonstrated in the provided example code snippet.\u003c/p\u003e\n"],["\u003cp\u003eThe page provides a list of specific versions, ranging from version \u003ccode\u003e2.11.0\u003c/code\u003e to \u003ccode\u003e2.37.0-rc\u003c/code\u003e, linking to their respective documentation regarding overriding authentication.\u003c/p\u003e\n"],["\u003cp\u003eExamples are provided for \u003ccode\u003espeech_v1::SpeechClient\u003c/code\u003e and \u003ccode\u003espeech_v2::SpeechClient\u003c/code\u003e classes.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices regarding service account keys, refer to the linked guide, and for more details on factory functions to create credentials, consult the Authentication Components section.\u003c/p\u003e\n"]]],[],null,[]]
