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::trace_v1::TraceServiceClient(
google::cloud::trace_v1::MakeTraceServiceConnection(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complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-08-14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, which is done by providing a \u003ccode\u003eUnifiedCredentialsOption\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eThe latest release candidate version available is \u003ccode\u003e2.37.0-rc\u003c/code\u003e, and this page has documentation spanning down to version \u003ccode\u003e2.11.0\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eAn example is shown that demonstrates explicitly loading a service account key file to override the default authentication for the \u003ccode\u003etrace_v1::TraceServiceClient\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eExamples for other client classes, specifically \u003ccode\u003etrace_v1::TraceServiceClient\u003c/code\u003e and \u003ccode\u003etrace_v2::TraceServiceClient\u003c/code\u003e, are linked and available for reference.\u003c/p\u003e\n"],["\u003cp\u003eFor best practices regarding managing service account keys, users are advised to consult the linked guide.\u003c/p\u003e\n"]]],[],null,[]]
