diff --git a/Demo App/Twift_SwiftUI/Twift_SwiftUIApp.swift b/Demo App/Twift_SwiftUI/Twift_SwiftUIApp.swift
index 33eaaea..589d059 100644
--- a/Demo App/Twift_SwiftUI/Twift_SwiftUIApp.swift	
+++ b/Demo App/Twift_SwiftUI/Twift_SwiftUIApp.swift	
@@ -13,6 +13,7 @@ extension Twift {
     switch authenticationType {
     case .appOnly(_): return false
     case .userAccessTokens(_, _): return true
+    case .oauth2UserContext(_): return true
     }
   }
 }
@@ -43,20 +44,26 @@ struct Twift_SwiftUIApp: App {
               header: Text("User Access Tokens"),
               footer: Text("Use this authentication method for most cases.")
             ) {
-              Button {
-                Twift.Authentication().requestUserCredentials(clientCredentials: clientCredentials, callbackURL: URL(string: TWITTER_CALLBACK_URL)!) { (userCredentials, error) in
-                  if let error = error {
-                    print(error.localizedDescription)
-                  }
-                  
-                  if let creds = userCredentials {
-                    DispatchQueue.main.async {
-                      container.client = Twift(.userAccessTokens(clientCredentials: clientCredentials, userCredentials: creds))
-                    }
-                  }
-                }
+//              Button {
+//                Twift.Authentication().requestUserCredentials(clientCredentials: clientCredentials, callbackURL: URL(string: TWITTER_CALLBACK_URL)!) { (userCredentials, error) in
+//                  if let error = error {
+//                    print(error.localizedDescription)
+//                  }
+//
+//                  if let creds = userCredentials {
+//                    DispatchQueue.main.async {
+//                      container.client = Twift(.userAccessTokens(clientCredentials: clientCredentials, userCredentials: creds))
+//                    }
+//                  }
+//                }
+//              } label: {
+//                Text("Sign In With Twitter")
+//              }
+              
+              AsyncButton {
+                let result = await Twift.Authentication().authorizeUser(clientId: "Sm5PSUhRNW9EZ3NXb0tJQkI5WU06MTpjaQ", redirectUri: URL(string: TWITTER_CALLBACK_URL)!, scope: [.offlineAccess, .usersRead, .tweetRead])
               } label: {
-                Text("Sign In With Twitter")
+                Text("Sign in")
               }
             }
             
diff --git a/Sources/Twift+API.swift b/Sources/Twift+API.swift
index 8cefdf0..cc02107 100644
--- a/Sources/Twift+API.swift
+++ b/Sources/Twift+API.swift
@@ -70,6 +70,8 @@ extension Twift {
         consumerCredentials: clientCredentials,
         userCredentials: userCredentials
       )
+    case .oauth2UserContext(let oauthUser):
+      request.addValue("Bearer \(oauthUser.accessToken)", forHTTPHeaderField: "Authorization")
     }
   }
 }
diff --git a/Sources/Twift+Authentication.swift b/Sources/Twift+Authentication.swift
index 1cf52f4..7a14919 100644
--- a/Sources/Twift+Authentication.swift
+++ b/Sources/Twift+Authentication.swift
@@ -14,6 +14,12 @@ extension Twift {
     case userAccessTokens(clientCredentials: OAuthCredentials,
                           userCredentials: OAuthCredentials)
     
+    
+    /// OAuth 2.0 User Context authentication.
+    ///
+    /// When this authentication method is used, the `oauth2User` access token may be automatically refreshed by the client if it has expired.
+    case oauth2UserContext(oauth2User: OAuth2User)
+    
     /// App-only authentication
     case appOnly(bearerToken: String)
   }
@@ -23,6 +29,9 @@ extension Twift {
     /// A value representing ``AuthenticationType.userAccessTokens(_, _)``
     case userAccessTokens
     
+    /// A value representing ``AuthenticationType.oauth2UserContext(_)``
+    case oauth2UserContext
+    
     /// A value representing ``AuthenticationType.appOnly(_)``
     case appOnly
   }
@@ -123,3 +132,168 @@ extension Twift {
     }
   }
 }
+
+extension Twift.Authentication {
+  public func authorizeUser(clientId: String,
+                            redirectUri: URL,
+                            scope: Set<OAuth2Scope>,
+                            presentationContextProvider: ASWebAuthenticationPresentationContextProviding? = nil
+  ) async -> (OAuth2User?, Error?) {
+    let state = UUID().uuidString
+    
+    let authUrlQueryItems: [URLQueryItem] = [
+      URLQueryItem(name: "response_type", value: "code"),
+      URLQueryItem(name: "client_id", value: clientId),
+      URLQueryItem(name: "redirect_uri", value: redirectUri.absoluteString),
+      URLQueryItem(name: "scope", value: scope.map(\.rawValue).joined(separator: " ")),
+      URLQueryItem(name: "state", value: state),
+      URLQueryItem(name: "code_challenge", value: "challenge"),
+      URLQueryItem(name: "code_challenge_method", value: "plain"),
+    ]
+    
+    var authUrl = URLComponents()
+    authUrl.scheme = "https"
+    authUrl.host = "twitter.com"
+    authUrl.path = "/i/oauth2/authorize"
+    authUrl.queryItems = authUrlQueryItems
+    
+    let (returnedUrl, error): (URL?, Error?) = await withCheckedContinuation { continuation in
+      guard let authUrl = authUrl.url else {
+        return continuation.resume(returning: (nil, TwiftError.UnknownError(nil)))
+      }
+
+      let authSession = ASWebAuthenticationSession(url: authUrl, callbackURLScheme: redirectUri.scheme) { (url, error) in
+        return continuation.resume(returning: (url, error))
+      }
+      
+      authSession.presentationContextProvider = presentationContextProvider ?? self
+      authSession.start()
+    }
+    
+    if let error = error {
+      print(error.localizedDescription)
+      return (nil, error)
+    }
+    
+    guard let returnedUrl = returnedUrl else {
+      return (nil, TwiftError.UnknownError("No returned OAuth URL"))
+    }
+    
+    let returnedUrlComponents = URLComponents(string: returnedUrl.absoluteString)
+    
+    let returnedState = returnedUrlComponents?.queryItems?.first(where: { $0.name == "state" })?.value
+    guard let returnedState = returnedState,
+          returnedState == state else {
+      return (nil, TwiftError.UnknownError("Bad state returned from OAuth flow"))
+    }
+
+    let returnedCode = returnedUrlComponents?.queryItems?.first(where: { $0.name == "code" })?.value
+    guard let returnedCode = returnedCode else {
+      return (nil, TwiftError.UnknownError("No code returned"))
+    }
+    
+    var codeRequest = URLRequest(url: URL(string: "https://api.twitter.com/2/oauth2/token")!)
+    let body = [
+      "code": returnedCode,
+      "grant_type": "authorization_code",
+      "client_id": clientId,
+      "redirect_uri": redirectUri.absoluteString,
+      "code_verifier": "challenge"
+    ]
+    
+    let encodedBody = try? JSONSerialization.data(withJSONObject: body)
+    
+    codeRequest.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
+    codeRequest.httpMethod = "POST"
+    codeRequest.httpBody = encodedBody
+    
+    do {
+      let (data, _) = try await URLSession.shared.data(for: codeRequest)
+      
+      print(String(data: data, encoding: .utf8))
+    } catch {
+      print(error.localizedDescription)
+    }
+    
+    return (nil, nil)
+  }
+}
+
+public struct OAuth2User {
+  public var clientId: String
+  public var userId: String?
+  public var accessToken: String
+  public var refreshToken: String?
+  public var expiresAt: Date
+  public var scope: [OAuth2Scope]
+  
+  public var expired: Bool {
+    expiresAt < .now
+  }
+}
+
+public enum OAuth2Scope: String, CaseIterable, RawRepresentable {
+  /// All the Tweets you can view, including Tweets from protected accounts.
+  case tweetRead = "tweet.read"
+  
+  /// Tweet and Retweet for you.
+  case tweetWrite = "tweet.write"
+  
+  /// Hide and unhide replies to your Tweets.
+  case tweetModerateWrite = "tweet.moderate.write"
+  
+  /// Any account you can view, including protected accounts.
+  case usersRead = "users.read"
+  
+  /// People who follow you and people who you follow.
+  case followsRead = "follows.read"
+  
+  /// Follow and unfollow people for you.
+  case followsWrite = "follows.write"
+  
+  /// Stay connected to your account until you revoke access.
+  case offlineAccess = "offline.access"
+  
+  /// All the Spaces you can view.
+  case spaceRead = "space.read"
+  
+  /// Accounts you’ve muted.
+  case muteRead = "mute.read"
+  
+  /// Mute and unmute accounts for you.
+  case muteWrite = "mute.write"
+  
+  /// Tweets you’ve liked and likes you can view.
+  case likeRead = "like.read"
+  
+  /// Like and un-like Tweets for you.
+  case likeWrite = "like.write"
+  
+  /// Lists, list members, and list followers of lists you’ve created or are a member of, including private lists.
+  case listRead = "list.read"
+  
+  /// Create and manage Lists for you.
+  case listWrite = "list.write"
+  
+  /// Accounts you’ve blocked.
+  case blockRead = "block.read"
+  
+  /// Block and unblock accounts for you.
+  case blockWrite = "block.write"
+  
+  /// Get Bookmarked Tweets from an authenticated user.
+  case bookmarkRead = "bookmark.read"
+  
+  /// Bookmark and remove Bookmarks from Tweets
+  case bookmarkWrite = "bookmark.write"
+  
+  /// All write-permission scopes.
+  static var allWriteScopes: Set<OAuth2Scope> {
+    [.likeWrite, .listWrite, .muteWrite, .blockWrite, .tweetWrite, .followsWrite, .bookmarkWrite, .tweetModerateWrite]
+  }
+  
+  /// All read-permission scopes.
+  static var allReadScopes: Set<OAuth2Scope> {
+    [.likeRead, .listRead, .muteRead, .blockRead, .spaceRead, .tweetRead, .usersRead, .followsRead, .bookmarkRead]
+  }
+}
diff --git a/Sources/Twift.swift b/Sources/Twift.swift
index cfa2dd3..6d4ac3a 100644
--- a/Sources/Twift.swift
+++ b/Sources/Twift.swift
@@ -25,6 +25,8 @@ public class Twift: NSObject, ObservableObject {
       return userCredentials.userId
     case .appOnly(_):
       return nil
+    case .oauth2UserContext(let user):
+      return user.userId
     }
   }