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::texttospeech_v1::TextToSpeechClient(
google::cloud::texttospeech_v1::MakeTextToSpeechConnection(options));
}
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Hard to understand","hardToUnderstand","thumb-down"],["Incorrect information or sample code","incorrectInformationOrSampleCode","thumb-down"],["Missing the information/samples I need","missingTheInformationSamplesINeed","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14 UTC."],[[["\u003cp\u003eThis webpage provides documentation for different versions of the Text-to-Speech C++ client library, ranging from the latest release candidate 2.37.0-rc down to version 2.11.0.\u003c/p\u003e\n"],["\u003cp\u003eThe default authentication method for the client libraries is Application Default Credentials, but this can be overridden.\u003c/p\u003e\n"],["\u003cp\u003eYou can override the default authentication by using \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e and providing alternative credentials, such as a service account key file, which is shown in the example.\u003c/p\u003e\n"],["\u003cp\u003eFor more information on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects, refer to the Authentication Components documentation.\u003c/p\u003e\n"],["\u003cp\u003eIt is recommended to consult the "Best practices for managing service account keys" guide for details on key management.\u003c/p\u003e\n"]]],[],null,[]]
