Deep

In FGO request, there are two important parameters related to user's device:

• UserAgent: in http headers. Probably FGO won't check it.
• deviceInfo: in login post body. FGO will record this value in server and verify it when user requests reset Transfer Code (引き継ぎナンバー) via email which will ask user to provide last played device.

TIP

The value also depends on Unity version, current FGO JP 2.87.0 uses 2020.3.34f1

UserAgent

On Android, get UA from system:

// Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1
System.getProperty("http.agent");

Example:

"Dalvik/2.1.0 (Linux; U; Android 8.1; SM-G9500 Build/V417IR)"  # MuMu
"Dalvik/2.1.0 (Linux; U; Android 7.1.2; V1938CT Build/N2G48C)" # LD5

f"Dalvik/2.1.0 (Linux; U; Android {version.release}; {model} Build/{id})"

On iOS, it defaults to the app's UserAgent (not sure)

"FateGO/2.80.5 CFNetwork/1474 Darwin/23.0.0"

f"FateGO/{fgover} CFNetwork/{cfnetworkver} Darwin/{utsname.release}"

deviceInfo

void __fastcall NetworkManager__SetDeviceInfoField(RequestBase_o *request, const MethodInfo *method)
{
  __int64 v3; // x1
  Il2CppObject *deviceModel; // x20
  Il2CppObject *operatingSystem; // x0
  System_String_o *v6; // x0

  deviceModel = (Il2CppObject *)UnityEngine_SystemInfo__get_deviceModel(0LL);
  operatingSystem = (Il2CppObject *)UnityEngine_SystemInfo__get_operatingSystem(0LL);
  v6 = System_String__Format_43739268((System_String_o *)StringLiteral_23458, deviceModel, operatingSystem, 0LL);
  RequestBase__addField_30957164(request, (System_String_o *)StringLiteral_17935, v6, 0LL);
}

Here format template is {0} / {1}.

deviceModel

Unity SystemInfo.deviceModel

On Android:

"samsung SM-G9500"
f"{manufacturer} {model}"

On iOS:

"iPhone6,1"

In device_info plugin is iosInfo.utsname.machine

operatingSystem

Unity SystemInfo.operatingSystem

On Android:

f"Android OS 7.1.2 / API-25 (N2G48C/4565141)"

f"Android OS {version.release} / API-{version.sdkInt} ({id}/{version.incremental})"

On iOS:

// Prints "iPhone OS" with iOS 15.3.1
// Prints "iPad OS" on iPad with iOS 16