diff --git a/FirebaseAuth/Sources/Swift/Backend/AuthBackend.swift b/FirebaseAuth/Sources/Swift/Backend/AuthBackend.swift
index 474f665147f..3c54b2792fd 100644
--- a/FirebaseAuth/Sources/Swift/Backend/AuthBackend.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/AuthBackend.swift
@@ -60,7 +60,8 @@ final class AuthBackend: AuthBackendProtocol {
     }
   }
 
-  static func request(withURL url: URL,
+  static func request(for url: URL,
+                      httpMethod: String,
                       contentType: String,
                       requestConfiguration: AuthRequestConfiguration) async -> URLRequest {
     // Kick off tasks for the async header values.
@@ -76,7 +77,7 @@ final class AuthBackend: AuthBackendProtocol {
     request.setValue(clientVersion, forHTTPHeaderField: "X-Client-Version")
     request.setValue(Bundle.main.bundleIdentifier, forHTTPHeaderField: "X-Ios-Bundle-Identifier")
     request.setValue(requestConfiguration.appID, forHTTPHeaderField: "X-Firebase-GMPID")
-    request.httpMethod = requestConfiguration.httpMethod
+    request.httpMethod = httpMethod
     let preferredLocalizations = Bundle.main.preferredLocalizations
     if preferredLocalizations.count > 0 {
       request.setValue(preferredLocalizations.first, forHTTPHeaderField: "Accept-Language")
@@ -163,21 +164,11 @@ final class AuthBackend: AuthBackendProtocol {
   /// - Returns: The response.
   fileprivate func callInternal<T: AuthRPCRequest>(with request: T) async throws -> T.Response {
     var bodyData: Data?
-    if request.containsPostBody {
-      var postBody: [String: AnyHashable]
-      do {
-        // TODO: Can unencodedHTTPRequestBody ever throw?
-        // They don't today, but there are a few fatalErrors that might better be implemented as
-        // thrown errors.. Although perhaps the case of 'containsPostBody' returning false could
-        // perhaps be modeled differently so that the failing unencodedHTTPRequestBody could only
-        // be called when a body exists...
-        postBody = try request.unencodedHTTPRequestBody()
-      } catch {
-        throw AuthErrorUtils.RPCRequestEncodingError(underlyingError: error)
-      }
-      var JSONWritingOptions: JSONSerialization.WritingOptions = .init(rawValue: 0)
+    if let postBody = request.unencodedHTTPRequestBody {
       #if DEBUG
-        JSONWritingOptions = JSONSerialization.WritingOptions.prettyPrinted
+        let JSONWritingOptions = JSONSerialization.WritingOptions.prettyPrinted
+      #else
+        let JSONWritingOptions = JSONSerialization.WritingOptions(rawValue: 0)
       #endif
 
       guard JSONSerialization.isValidJSONObject(postBody) else {
diff --git a/FirebaseAuth/Sources/Swift/Backend/AuthBackendRPCIssuer.swift b/FirebaseAuth/Sources/Swift/Backend/AuthBackendRPCIssuer.swift
index 6d2c540ff37..bcf4f6dcab8 100644
--- a/FirebaseAuth/Sources/Swift/Backend/AuthBackendRPCIssuer.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/AuthBackendRPCIssuer.swift
@@ -52,9 +52,12 @@ final class AuthBackendRPCIssuer: AuthBackendRPCIssuerProtocol {
                                          body: Data?,
                                          contentType: String) async -> (Data?, Error?) {
     let requestConfiguration = request.requestConfiguration()
-    let request = await AuthBackend.request(withURL: request.requestURL(),
-                                            contentType: contentType,
-                                            requestConfiguration: requestConfiguration)
+    let request = await AuthBackend.request(
+      for: request.requestURL(),
+      httpMethod: body == nil ? "GET" : "POST",
+      contentType: contentType,
+      requestConfiguration: requestConfiguration
+    )
     let fetcher = fetcherService.fetcher(with: request)
     if let _ = requestConfiguration.emulatorHostAndPort {
       fetcher.allowLocalhostRequest = true
diff --git a/FirebaseAuth/Sources/Swift/Backend/AuthRPCRequest.swift b/FirebaseAuth/Sources/Swift/Backend/AuthRPCRequest.swift
index 34f40d82f88..eeacfbea897 100644
--- a/FirebaseAuth/Sources/Swift/Backend/AuthRPCRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/AuthRPCRequest.swift
@@ -22,14 +22,11 @@ protocol AuthRPCRequest {
   /// Gets the request's full URL.
   func requestURL() -> URL
 
-  /// Returns whether the request contains a post body or not. Requests without a post body are
-  /// GET requests. A default implementation returns `true`.
-  var containsPostBody: Bool { get }
-
   /// Creates unencoded HTTP body representing the request.
-  /// - Throws: Any error which occurred constructing the request.
   /// - Returns: The HTTP body data representing the request before any encoding.
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable]
+  /// - Note: Requests with a post body are POST requests. Requests without a
+  /// post body are GET requests.
+  var unencodedHTTPRequestBody: [String: AnyHashable]? { get }
 
   /// The request configuration.
   func requestConfiguration() -> AuthRequestConfiguration
@@ -41,7 +38,6 @@ protocol AuthRPCRequest {
 // in Obj-C.
 @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
 extension AuthRPCRequest {
-  var containsPostBody: Bool { return true }
   func injectRecaptchaFields(recaptchaResponse: String?, recaptchaVersion: String) {
     fatalError("Internal FirebaseAuth Error: unimplemented injectRecaptchaFields")
   }
diff --git a/FirebaseAuth/Sources/Swift/Backend/AuthRequestConfiguration.swift b/FirebaseAuth/Sources/Swift/Backend/AuthRequestConfiguration.swift
index 47aff1be47e..510e9287ca0 100644
--- a/FirebaseAuth/Sources/Swift/Backend/AuthRequestConfiguration.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/AuthRequestConfiguration.swift
@@ -38,9 +38,6 @@ class AuthRequestConfiguration {
   /// The appCheck is used to generate a token.
   var appCheck: AppCheckInterop?
 
-  /// The HTTP method used in the request.
-  var httpMethod: String
-
   /// Additional framework marker that will be added as part of the header of every request.
   var additionalFrameworkMarker: String?
 
@@ -57,6 +54,5 @@ class AuthRequestConfiguration {
     self.auth = auth
     self.heartbeatLogger = heartbeatLogger
     self.appCheck = appCheck
-    httpMethod = "POST"
   }
 }
diff --git a/FirebaseAuth/Sources/Swift/Backend/IdentityToolkitRequest.swift b/FirebaseAuth/Sources/Swift/Backend/IdentityToolkitRequest.swift
index 3a5d5a3b18a..08f9f9f30d6 100644
--- a/FirebaseAuth/Sources/Swift/Backend/IdentityToolkitRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/IdentityToolkitRequest.swift
@@ -70,8 +70,6 @@ class IdentityToolkitRequest {
     tenantID = requestConfiguration.auth?.tenantID
   }
 
-  var containsPostBody: Bool { return true }
-
   func queryParams() -> String {
     return ""
   }
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/CreateAuthURIRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/CreateAuthURIRequest.swift
index 419419f4862..987b7d28fe6 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/CreateAuthURIRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/CreateAuthURIRequest.swift
@@ -78,7 +78,7 @@ class CreateAuthURIRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kCreateAuthURIEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [
       kIdentifierKey: identifier,
       kContinueURIKey: continueURI,
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/DeleteAccountRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/DeleteAccountRequest.swift
index 81856a0c027..543d5af3b8f 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/DeleteAccountRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/DeleteAccountRequest.swift
@@ -41,7 +41,7 @@ class DeleteAccountRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kDeleteAccountEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     [
       kIDTokenKey: accessToken,
       kLocalIDKey: localID,
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/EmailLinkSignInRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/EmailLinkSignInRequest.swift
index b57c2170450..72a23517985 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/EmailLinkSignInRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/EmailLinkSignInRequest.swift
@@ -51,7 +51,7 @@ class EmailLinkSignInRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kEmailLinkSigninEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [
       kEmailKey: email,
       kOOBCodeKey: oobCode,
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/GetAccountInfoRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/GetAccountInfoRequest.swift
index 3e30fae5242..5dba854b172 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/GetAccountInfoRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/GetAccountInfoRequest.swift
@@ -39,7 +39,7 @@ class GetAccountInfoRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kGetAccountInfoEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     return [kIDTokenKey: accessToken]
   }
 }
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/GetOOBConfirmationCodeRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/GetOOBConfirmationCodeRequest.swift
index c1de49fd071..e2437a569bd 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/GetOOBConfirmationCodeRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/GetOOBConfirmationCodeRequest.swift
@@ -228,7 +228,7 @@ class GetOOBConfirmationCodeRequest: IdentityToolkitRequest, AuthRPCRequest {
          requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var body: [String: AnyHashable] = [
       kRequestTypeKey: requestType.value,
     ]
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/GetProjectConfigRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/GetProjectConfigRequest.swift
index 1b8f714b60e..1a1b011ff01 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/GetProjectConfigRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/GetProjectConfigRequest.swift
@@ -15,7 +15,6 @@
 import Foundation
 
 /// The "getProjectConfig" endpoint.
-
 private let kGetProjectConfigEndPoint = "getProjectConfig"
 
 @available(iOS 13, tvOS 13, macOS 10.15, macCatalyst 13, watchOS 7, *)
@@ -23,14 +22,10 @@ class GetProjectConfigRequest: IdentityToolkitRequest, AuthRPCRequest {
   typealias Response = GetProjectConfigResponse
 
   init(requestConfiguration: AuthRequestConfiguration) {
-    requestConfiguration.httpMethod = "GET"
     super.init(endpoint: kGetProjectConfigEndPoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
-    // TODO: Probably nicer to throw, but what should we throw?
-    fatalError()
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
+    nil
   }
-
-  override var containsPostBody: Bool { return false }
 }
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/GetRecaptchaConfigRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/GetRecaptchaConfigRequest.swift
index fc8e287a52f..075d8273a15 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/GetRecaptchaConfigRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/GetRecaptchaConfigRequest.swift
@@ -48,7 +48,6 @@ class GetRecaptchaConfigRequest: IdentityToolkitRequest, AuthRPCRequest {
   typealias Response = GetRecaptchaConfigResponse
 
   required init(requestConfiguration: AuthRequestConfiguration) {
-    requestConfiguration.httpMethod = "GET"
     super.init(
       endpoint: kGetRecaptchaConfigEndpoint,
       requestConfiguration: requestConfiguration,
@@ -56,12 +55,10 @@ class GetRecaptchaConfigRequest: IdentityToolkitRequest, AuthRPCRequest {
     )
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
-    return [:]
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
+    nil
   }
 
-  override var containsPostBody: Bool { return false }
-
   override func queryParams() -> String {
     var queryParams = "&\(kClientTypeKey)=\(clientType)&\(kVersionKey)=\(kRecaptchaVersion)"
     if let tenantID {
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/FinalizeMFAEnrollmentRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/FinalizeMFAEnrollmentRequest.swift
index 89374c9de4f..0c1154d5a68 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/FinalizeMFAEnrollmentRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/FinalizeMFAEnrollmentRequest.swift
@@ -71,7 +71,7 @@ class FinalizeMFAEnrollmentRequest: IdentityToolkitRequest, AuthRPCRequest {
     )
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var body: [String: AnyHashable] = [:]
     if let idToken = idToken {
       body["idToken"] = idToken
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/StartMFAEnrollmentRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/StartMFAEnrollmentRequest.swift
index 3896ec14b3d..467733768fc 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/StartMFAEnrollmentRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Enroll/StartMFAEnrollmentRequest.swift
@@ -64,7 +64,7 @@ class StartMFAEnrollmentRequest: IdentityToolkitRequest, AuthRPCRequest {
     )
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var body: [String: AnyHashable] = [:]
     if let idToken = idToken {
       body["idToken"] = idToken
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/FinalizeMFASignInRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/FinalizeMFASignInRequest.swift
index 399e426d456..7e8b67eca96 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/FinalizeMFASignInRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/FinalizeMFASignInRequest.swift
@@ -36,7 +36,7 @@ class FinalizeMFASignInRequest: IdentityToolkitRequest, AuthRPCRequest {
                useIdentityPlatform: true)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var body: [String: AnyHashable] = [:]
     if let mfaPendingCredential = mfaPendingCredential {
       body["mfaPendingCredential"] = mfaPendingCredential
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/StartMFASignInRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/StartMFASignInRequest.swift
index 1098c2ef4ea..82e1a1721bd 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/StartMFASignInRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/SignIn/StartMFASignInRequest.swift
@@ -41,7 +41,7 @@ class StartMFASignInRequest: IdentityToolkitRequest, AuthRPCRequest {
     )
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var body: [String: AnyHashable] = [:]
     if let MFAPendingCredential = MFAPendingCredential {
       body["mfaPendingCredential"] = MFAPendingCredential
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Unenroll/WithdrawMFARequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Unenroll/WithdrawMFARequest.swift
index 19d9a04faed..f2324db3ca2 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Unenroll/WithdrawMFARequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/MultiFactor/Unenroll/WithdrawMFARequest.swift
@@ -36,7 +36,7 @@ class WithdrawMFARequest: IdentityToolkitRequest, AuthRPCRequest {
                useIdentityPlatform: true)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [:]
     if let idToken = idToken {
       postBody["idToken"] = idToken
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/ResetPasswordRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/ResetPasswordRequest.swift
index aa39c927b83..c0b2629683d 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/ResetPasswordRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/ResetPasswordRequest.swift
@@ -48,7 +48,7 @@ class ResetPasswordRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kResetPasswordEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [:]
 
     postBody[kOOBCodeKey] = oobCode
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/RevokeTokenRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/RevokeTokenRequest.swift
index c3afae3b573..94e6deeeabb 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/RevokeTokenRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/RevokeTokenRequest.swift
@@ -71,7 +71,7 @@ class RevokeTokenRequest: IdentityToolkitRequest, AuthRPCRequest {
                useIdentityPlatform: true)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     let body: [String: AnyHashable] = [
       kProviderIDKey: providerID,
       kTokenTypeKey: "\(tokenType.rawValue)",
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/SecureTokenRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/SecureTokenRequest.swift
index d11275dcf29..175b1889b96 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/SecureTokenRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/SecureTokenRequest.swift
@@ -134,9 +134,7 @@ class SecureTokenRequest: AuthRPCRequest {
     return URL(string: urlString)!
   }
 
-  var containsPostBody: Bool { return true }
-
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [
       kGrantTypeKey: grantType.value,
     ]
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/SendVerificationTokenRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/SendVerificationTokenRequest.swift
index af090fdd3b3..a87ff833c10 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/SendVerificationTokenRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/SendVerificationTokenRequest.swift
@@ -60,7 +60,7 @@ class SendVerificationCodeRequest: IdentityToolkitRequest, AuthRPCRequest {
     )
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [:]
     postBody[kPhoneNumberKey] = phoneNumber
     switch codeIdentity {
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/SetAccountInfoRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/SetAccountInfoRequest.swift
index 82842ace520..5e310d4a656 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/SetAccountInfoRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/SetAccountInfoRequest.swift
@@ -136,7 +136,7 @@ class SetAccountInfoRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kSetAccountInfoEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [:]
     if let accessToken {
       postBody[kIDTokenKey] = accessToken
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/SignInWithGameCenterRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/SignInWithGameCenterRequest.swift
index adab76dcd34..7d722326f71 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/SignInWithGameCenterRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/SignInWithGameCenterRequest.swift
@@ -76,7 +76,7 @@ class SignInWithGameCenterRequest: IdentityToolkitRequest, AuthRPCRequest {
     )
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [
       "playerId": playerID,
       "publicKeyUrl": publicKeyURL.absoluteString,
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/SignUpNewUserRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/SignUpNewUserRequest.swift
index 12308573334..68cfe6b5e38 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/SignUpNewUserRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/SignUpNewUserRequest.swift
@@ -89,7 +89,7 @@ class SignUpNewUserRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kSignupNewUserEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [:]
     if let email {
       postBody[kEmailKey] = email
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyAssertionRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyAssertionRequest.swift
index 9e8d8b6b86d..30c924ff403 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyAssertionRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyAssertionRequest.swift
@@ -135,7 +135,7 @@ class VerifyAssertionRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kVerifyAssertionEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var components = URLComponents()
     var queryItems: [URLQueryItem] = [URLQueryItem(name: kProviderIDKey, value: providerID)]
     if let providerIDToken = providerIDToken {
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyCustomTokenRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyCustomTokenRequest.swift
index af1518ee653..b8a97278908 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyCustomTokenRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyCustomTokenRequest.swift
@@ -40,7 +40,7 @@ class VerifyCustomTokenRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kVerifyCustomTokenEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [
       kTokenKey: token,
     ]
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPasswordRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPasswordRequest.swift
index 2c9fc19d17c..4c1096d5fbe 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPasswordRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPasswordRequest.swift
@@ -79,7 +79,7 @@ class VerifyPasswordRequest: IdentityToolkitRequest, AuthRPCRequest {
     super.init(endpoint: kVerifyPasswordEndpoint, requestConfiguration: requestConfiguration)
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var body: [String: AnyHashable] = [
       kEmailKey: email,
       kPasswordKey: password,
diff --git a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPhoneNumberRequest.swift b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPhoneNumberRequest.swift
index 791c6fc9e01..07ddf167527 100644
--- a/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPhoneNumberRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/RPC/VerifyPhoneNumberRequest.swift
@@ -133,7 +133,7 @@ class VerifyPhoneNumberRequest: IdentityToolkitRequest, AuthRPCRequest {
     )
   }
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody: [String: AnyHashable] = [:]
     if let verificationID {
       postBody[kVerificationIDKey] = verificationID
diff --git a/FirebaseAuth/Sources/Swift/Backend/VerifyClientRequest.swift b/FirebaseAuth/Sources/Swift/Backend/VerifyClientRequest.swift
index f62f9def230..5821fc55c7e 100644
--- a/FirebaseAuth/Sources/Swift/Backend/VerifyClientRequest.swift
+++ b/FirebaseAuth/Sources/Swift/Backend/VerifyClientRequest.swift
@@ -27,7 +27,7 @@ class VerifyClientRequest: IdentityToolkitRequest, AuthRPCRequest {
   /// The key for the isSandbox request parameter.
   private static let isSandboxKey = "isSandbox"
 
-  func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
+  var unencodedHTTPRequestBody: [String: AnyHashable]? {
     var postBody = [String: AnyHashable]()
     if let appToken = appToken {
       postBody[Self.appTokenKey] = appToken
diff --git a/FirebaseAuth/Tests/Unit/AuthBackendTests.swift b/FirebaseAuth/Tests/Unit/AuthBackendTests.swift
index 5feaf239e3b..6056bbae362 100644
--- a/FirebaseAuth/Tests/Unit/AuthBackendTests.swift
+++ b/FirebaseAuth/Tests/Unit/AuthBackendTests.swift
@@ -50,13 +50,7 @@ class AuthBackendTests: RPCBaseTests {
 
       let underlyingError = try XCTUnwrap(rpcError.userInfo[NSUnderlyingErrorKey] as? NSError)
       XCTAssertEqual(underlyingError.domain, AuthErrorUtils.internalErrorDomain)
-      XCTAssertEqual(underlyingError.code, AuthInternalErrorCode.RPCRequestEncodingError.rawValue)
-
-      let underlyingUnderlying = try XCTUnwrap(underlyingError
-        .userInfo[NSUnderlyingErrorKey] as? NSError)
-      XCTAssertEqual(underlyingUnderlying.domain, kFakeErrorDomain)
-      XCTAssertEqual(underlyingUnderlying.code, kFakeErrorCode)
-
+      XCTAssertEqual(underlyingError.code, AuthInternalErrorCode.JSONSerializationError.rawValue)
       XCTAssertNil(underlyingError.userInfo[AuthErrorUtils.userInfoDeserializedResponseKey])
       XCTAssertNil(underlyingError.userInfo[AuthErrorUtils.userInfoDataKey])
     }
@@ -670,11 +664,17 @@ class AuthBackendTests: RPCBaseTests {
       return try! XCTUnwrap(URL(string: kFakeRequestURL))
     }
 
-    func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
-      if let encodingError {
-        throw encodingError
+    var unencodedHTTPRequestBody: [String: AnyHashable]? {
+      if encodingError == nil {
+        return requestBody
       }
-      return requestBody
+      // Else, return an unencodable request body that will cause an error to be thrown.
+      struct UnencodableObject: Hashable {
+        static func == (lhs: UnencodableObject, rhs: UnencodableObject) -> Bool {
+          true
+        }
+      }
+      return ["foo": UnencodableObject()]
     }
 
     static func makeRequestConfiguration() -> AuthRequestConfiguration {
@@ -684,8 +684,6 @@ class AuthBackendTests: RPCBaseTests {
       )
     }
 
-    var containsPostBody: Bool { return true }
-
     private let configuration: AuthRequestConfiguration
 
     let encodingError: NSError?
@@ -724,8 +722,8 @@ class AuthBackendTests: RPCBaseTests {
       return fakeRequest.requestURL()
     }
 
-    func unencodedHTTPRequestBody() throws -> [String: AnyHashable] {
-      return try fakeRequest.unencodedHTTPRequestBody()
+    var unencodedHTTPRequestBody: [String: AnyHashable]? {
+      fakeRequest.unencodedHTTPRequestBody
     }
 
     func requestConfiguration() -> FirebaseAuth.AuthRequestConfiguration {
diff --git a/FirebaseAuth/Tests/Unit/Fakes/FakeBackendRPCIssuer.swift b/FirebaseAuth/Tests/Unit/Fakes/FakeBackendRPCIssuer.swift
index 3a40aac37d7..9131a19f98f 100644
--- a/FirebaseAuth/Tests/Unit/Fakes/FakeBackendRPCIssuer.swift
+++ b/FirebaseAuth/Tests/Unit/Fakes/FakeBackendRPCIssuer.swift
@@ -148,9 +148,13 @@ final class FakeBackendRPCIssuer: AuthBackendRPCIssuerProtocol, @unchecked Senda
       // Use the real implementation so that the complete request can
       // be verified during testing.
       completeRequest = Task {
-        await AuthBackend.request(withURL: requestURL!,
-                                  contentType: contentType,
-                                  requestConfiguration: request.requestConfiguration())
+        await AuthBackend
+          .request(
+            for: request.requestURL(),
+            httpMethod: requestData == nil ? "GET" : "POST",
+            contentType: contentType,
+            requestConfiguration: request.requestConfiguration()
+          )
       }
       decodedRequest = try? JSONSerialization.jsonObject(with: body) as? [String: Any]
     }
diff --git a/FirebaseAuth/Tests/Unit/GetRecaptchaConfigTests.swift b/FirebaseAuth/Tests/Unit/GetRecaptchaConfigTests.swift
index 75149c38d45..6638d6bfcc1 100644
--- a/FirebaseAuth/Tests/Unit/GetRecaptchaConfigTests.swift
+++ b/FirebaseAuth/Tests/Unit/GetRecaptchaConfigTests.swift
@@ -25,7 +25,7 @@ class GetRecaptchaConfigTests: RPCBaseTests {
   func testGetRecaptchaConfigRequest() async throws {
     let request = GetRecaptchaConfigRequest(requestConfiguration: makeRequestConfiguration())
     //    let _ = try await authBackend.call(with: request)
-    XCTAssertFalse(request.containsPostBody)
+    XCTAssertNil(request.unencodedHTTPRequestBody)
 
     // Confirm that the request has no decoded body as it is get request.
     XCTAssertNil(rpcIssuer.decodedRequest)
diff --git a/FirebaseAuth/Tests/Unit/RPCBaseTests.swift b/FirebaseAuth/Tests/Unit/RPCBaseTests.swift
index 9a8f9026ea9..bb7a247fadf 100644
--- a/FirebaseAuth/Tests/Unit/RPCBaseTests.swift
+++ b/FirebaseAuth/Tests/Unit/RPCBaseTests.swift
@@ -91,7 +91,7 @@ class RPCBaseTests: XCTestCase {
     rpcIssuer.respondBlock = {
       XCTAssertEqual(self.rpcIssuer.requestURL?.absoluteString, expected)
       if checkPostBody {
-        XCTAssertFalse(request.containsPostBody)
+        XCTAssertNil(request.unencodedHTTPRequestBody)
       } else if let requestDictionary = self.rpcIssuer.decodedRequest as? [String: AnyHashable] {
         XCTAssertEqual(requestDictionary[key], value)
       } else {