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::vision_v1::ImageAnnotatorClient(
google::cloud::vision_v1::MakeImageAnnotatorConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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 when using C++ client libraries.\u003c/p\u003e\n"],["\u003cp\u003eThe latest version of the C++ client library for vision is \u003ccode\u003e2.37.0-rc\u003c/code\u003e, with various other versions from \u003ccode\u003e2.36.0\u003c/code\u003e to \u003ccode\u003e2.11.0\u003c/code\u003e also listed for reference.\u003c/p\u003e\n"],["\u003cp\u003eAuthentication can be overridden by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e, as shown in the example using a service account key file.\u003c/p\u003e\n"],["\u003cp\u003eExamples for \u003ccode\u003evision_v1::ImageAnnotatorClient\u003c/code\u003e and \u003ccode\u003evision_v1::ProductSearchClient\u003c/code\u003e are provided to illustrate how to set up service account credentials.\u003c/p\u003e\n"],["\u003cp\u003eThe document also recommends consulting the "Best practices for managing service account keys" guide and provides a link to "Authentication Components" for further details on creating \u003ccode\u003egoogle::cloud::Credentials\u003c/code\u003e objects.\u003c/p\u003e\n"]]],[],null,[]]
