diff --git a/src/SvelteAuth/auth.ts b/src/SvelteAuth/auth.ts
new file mode 100644
index 0000000..7f4ace2
--- /dev/null
+++ b/src/SvelteAuth/auth.ts
@@ -0,0 +1,201 @@
+import type { GetSession, RequestHandler } from "@sveltejs/kit";
+import type { EndpointOutput, ServerRequest } from "@sveltejs/kit/types/endpoint";
+import type { Headers } from "@sveltejs/kit/types/helper";
+import cookie from "cookie";
+import * as jsonwebtoken from "jsonwebtoken";
+import type { JWT, Session } from "./interfaces";
+import type { Provider } from "./providers";
+
+interface AuthConfig {
+  providers?: Provider[];
+  callbacks?: AuthCallbacks;
+  jwtSecret?: string;
+  jwtExpiresIn?: string | number;
+}
+
+interface AuthCallbacks {
+  signIn?: () => boolean | Promise<boolean>;
+  jwt?: (token: JWT, profile?: any) => JWT | Promise<JWT>;
+  session?: (token: JWT, session: Session) => Session | Promise<Session>;
+  redirect?: (url: string) => string | Promise<string>;
+}
+
+export class Auth {
+  constructor(private readonly config?: AuthConfig) {}
+
+  getJwtSecret() {
+    if (this.config?.jwtSecret) {
+      return this.config?.jwtSecret;
+    }
+
+    if (this.config?.providers?.length) {
+      const provs = this.config?.providers?.map((provider) => provider.id).join("+");
+      return Buffer.from(provs).toString("base64");
+    }
+
+    return "svelte_auth_secret";
+  }
+
+  async getToken(headers: Headers) {
+    if (!headers.cookie) {
+      return null;
+    }
+
+    const cookies = cookie.parse(headers.cookie);
+
+    if (!cookies.svelteauthjwt) {
+      return null;
+    }
+
+    let token: JWT;
+    try {
+      token = (jsonwebtoken.verify(cookies.svelteauthjwt, this.getJwtSecret()) || {}) as JWT;
+    } catch {
+      return null;
+    }
+
+    if (this.config?.callbacks?.jwt) {
+      token = await this.config.callbacks.jwt(token);
+    }
+
+    return token;
+  }
+
+  getBaseUrl(host: string) {
+    return `http://${host}`;
+  }
+
+  setToken(headers: Headers, newToken: JWT | any) {
+    const originalToken = this.getToken(headers);
+
+    return {
+      ...(originalToken ?? {}),
+      ...newToken,
+    };
+  }
+
+  signToken(token: JWT) {
+    const opts = !token.exp
+      ? {
+          expiresIn: this.config?.jwtExpiresIn ?? "30d",
+        }
+      : {};
+    const jwt = jsonwebtoken.sign(token, this.getJwtSecret(), opts);
+    return jwt;
+  }
+
+  async getRedirectUrl(host: string, redirectUrl?: string) {
+    let redirect = redirectUrl || this.getBaseUrl(host);
+    if (this.config?.callbacks?.redirect) {
+      redirect = await this.config.callbacks.redirect(redirect);
+    }
+    return redirect;
+  }
+
+  async handleProviderCallback(
+    request: ServerRequest,
+    provider: Provider,
+  ): Promise<EndpointOutput> {
+    const { headers, host } = request;
+    const [profile, redirectUrl] = await provider.callback(request);
+
+    let token = (await this.getToken(headers)) ?? { user: {} };
+    if (this.config?.callbacks?.jwt) {
+      token = await this.config.callbacks.jwt(token, profile);
+    } else {
+      token = this.setToken(headers, { user: profile });
+    }
+
+    const jwt = this.signToken(token);
+    console.log(jwt);
+    const redirect = await this.getRedirectUrl(host, redirectUrl);
+
+    return {
+      status: 302,
+      headers: {
+        "set-cookie": `svelteauthjwt=${jwt}; Path=/; HttpOnly`,
+        Location: redirect,
+      },
+    };
+  }
+
+  async handleEndpoint(request: ServerRequest): Promise<EndpointOutput> {
+    const { path, headers, method, host } = request;
+
+    if (path === "/api/auth/signout") {
+      const token = this.setToken(headers, {});
+      const jwt = this.signToken(token);
+
+      if (method === "POST") {
+        return {
+          headers: {
+            "set-cookie": `svelteauthjwt=${jwt}; Path=/; HttpOnly`,
+          },
+          body: {
+            signout: true,
+          },
+        };
+      }
+
+      const redirect = await this.getRedirectUrl(host);
+
+      return {
+        status: 302,
+        headers: {
+          "set-cookie": `svelteauthjwt=${jwt}; Path=/; HttpOnly`,
+          Location: redirect,
+        },
+      };
+    }
+
+    const match = path.match(/\/api\/auth\/(?<method>signin|callback)\/(?<provider>\w+)/);
+
+    if (match) {
+      const provider = this.config?.providers?.find(
+        (provider) => provider.id === match.groups.provider,
+      );
+      if (provider) {
+        if (match.groups.method === "signin") {
+          return await provider.signin(request);
+        } else {
+          return await this.handleProviderCallback(request, provider);
+        }
+      }
+    }
+  }
+
+  get: RequestHandler = async (request) => {
+    const { path } = request;
+
+    if (path === "/api/auth/csrf") {
+      return { body: "1234" }; // TODO: Generate real token
+    } else if (path === "/api/auth/session") {
+      const session = await this.getSession(request);
+      return {
+        body: {
+          session,
+        },
+      };
+    }
+
+    return await this.handleEndpoint(request);
+  };
+
+  post: RequestHandler = async (request) => {
+    return await this.handleEndpoint(request);
+  };
+
+  getSession: GetSession = async ({ headers }) => {
+    const token = await this.getToken(headers);
+
+    if (token) {
+      if (this.config?.callbacks?.session) {
+        return await this.config.callbacks.session(token, { user: token.user });
+      }
+
+      return { user: token.user };
+    }
+
+    return {};
+  };
+}
diff --git a/src/SvelteAuth/client/index.ts b/src/SvelteAuth/client/index.ts
new file mode 100644
index 0000000..df0a8ef
--- /dev/null
+++ b/src/SvelteAuth/client/index.ts
@@ -0,0 +1,2 @@
+export { signIn } from "./signIn";
+export { signOut } from "./signOut";
diff --git a/src/SvelteAuth/client/signIn.ts b/src/SvelteAuth/client/signIn.ts
new file mode 100644
index 0000000..be97123
--- /dev/null
+++ b/src/SvelteAuth/client/signIn.ts
@@ -0,0 +1,38 @@
+import { goto } from "$app/navigation";
+import { page } from "$app/stores";
+import type { Page } from "@sveltejs/kit";
+
+interface SignInConfig {
+  redirectUrl?: string;
+}
+
+export async function signIn(provider: string, data?: any, config?: SignInConfig) {
+  if (data) {
+    const path = `/api/auth/callback/${provider}`;
+    const res = await fetch(path, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify(data),
+    });
+    return await res.json();
+  }
+
+  let redirectUrl: string;
+  if (config?.redirectUrl) {
+    redirectUrl = config.redirectUrl;
+  } else {
+    let $val: Page;
+    page.subscribe(($) => ($val = $))();
+    redirectUrl = `${$val.host}${$val.path}?${$val.query}`;
+  }
+
+  const queryData = {
+    redirect: redirectUrl,
+  };
+  const query = new URLSearchParams(queryData);
+  const path = `/api/auth/login/${provider}?${query}`;
+
+  return await goto(path);
+}
diff --git a/src/SvelteAuth/client/signOut.ts b/src/SvelteAuth/client/signOut.ts
new file mode 100644
index 0000000..564ab69
--- /dev/null
+++ b/src/SvelteAuth/client/signOut.ts
@@ -0,0 +1,12 @@
+import { session as session$ } from "$app/stores";
+
+export async function signOut() {
+  const res = await fetch("/api/auth/signout", { method: "POST" });
+  const { signout } = await res.json();
+
+  fetch("/api/auth/session")
+    .then((res) => res.json())
+    .then(session$.set);
+
+  return signout === true;
+}
diff --git a/src/SvelteAuth/index.ts b/src/SvelteAuth/index.ts
new file mode 100644
index 0000000..3223cc5
--- /dev/null
+++ b/src/SvelteAuth/index.ts
@@ -0,0 +1,2 @@
+export { Auth } from "./auth";
+export { Provider } from "./providers";
diff --git a/src/SvelteAuth/interfaces.ts b/src/SvelteAuth/interfaces.ts
new file mode 100644
index 0000000..df133b4
--- /dev/null
+++ b/src/SvelteAuth/interfaces.ts
@@ -0,0 +1,13 @@
+export interface JWT {
+  user: User;
+  [key: string]: any;
+}
+
+export interface User {
+  [key: string]: any;
+}
+
+export interface Session {
+  user: User;
+  [key: string]: any;
+}
diff --git a/src/SvelteAuth/providers/base.ts b/src/SvelteAuth/providers/base.ts
new file mode 100644
index 0000000..4d84d54
--- /dev/null
+++ b/src/SvelteAuth/providers/base.ts
@@ -0,0 +1,32 @@
+import type { EndpointOutput } from "@sveltejs/kit";
+import type { ServerRequest } from "@sveltejs/kit/types/endpoint";
+import type { CallbackResult } from "../types";
+
+export interface ProviderConfig {
+  id?: string;
+  profile?: (profile: any, account: any) => any | Promise<any>;
+}
+
+export abstract class Provider<T extends ProviderConfig = ProviderConfig> {
+  id: string;
+
+  constructor(protected readonly config: T) {
+    this.id = config.id;
+  }
+
+  getUri(host: string, path: string) {
+    return `http://${host}${path}`;
+  }
+
+  getCallbackUri(host: string) {
+    return this.getUri(host, `${"/api/auth/callback/"}${this.id}`);
+  }
+
+  abstract signin<Locals extends Record<string, any> = Record<string, any>, Body = unknown>(
+    request: ServerRequest<Locals, Body>,
+  ): EndpointOutput | Promise<EndpointOutput>;
+
+  abstract callback<Locals extends Record<string, any> = Record<string, any>, Body = unknown>(
+    request: ServerRequest<Locals, Body>,
+  ): CallbackResult | Promise<CallbackResult>;
+}
diff --git a/src/SvelteAuth/providers/facebook.ts b/src/SvelteAuth/providers/facebook.ts
new file mode 100644
index 0000000..c012b64
--- /dev/null
+++ b/src/SvelteAuth/providers/facebook.ts
@@ -0,0 +1,78 @@
+import type { ServerRequest } from "@sveltejs/kit/types/endpoint";
+import { OAuth2Provider, OAuth2ProviderConfig } from "./oauth2";
+
+interface FacebookAuthProviderConfig extends OAuth2ProviderConfig {
+  clientId: string;
+  clientSecret: string;
+  userProfileFields?: string;
+  scope?: string;
+}
+
+const defaultConfig: Partial<FacebookAuthProviderConfig> = {
+  id: "facebook",
+  scope: "email public_profile user_link",
+  userProfileFields:
+    "id,name,first_name,last_name,middle_name,name_format,picture,short_name,email",
+};
+
+export class FacebookAuthProvider extends OAuth2Provider<FacebookAuthProviderConfig> {
+  constructor(config: FacebookAuthProviderConfig) {
+    super({
+      ...defaultConfig,
+      ...config,
+    });
+  }
+
+  getSigninUrl({ host }: ServerRequest, state: string) {
+    const endpoint = "https://www.facebook.com/v10.0/dialog/oauth";
+
+    const data = {
+      client_id: this.config.clientId,
+      scope: this.config.scope,
+      redirect_uri: this.getCallbackUri(host),
+      state,
+    };
+
+    const url = `${endpoint}?${new URLSearchParams(data)}`;
+    return url;
+  }
+
+  async getTokens(code: string, redirectUri: string) {
+    const endpoint = "https://graph.facebook.com/v10.0/oauth/access_token";
+
+    const data = {
+      code,
+      client_id: this.config.clientId,
+      redirect_uri: redirectUri,
+      client_secret: this.config.clientSecret,
+    };
+
+    const res = await fetch(`${endpoint}?${new URLSearchParams(data)}`);
+    return await res.json();
+  }
+
+  async inspectToken(tokens: any) {
+    const endpoint = "https://graph.facebook.com/debug_token";
+
+    const data = {
+      input_token: tokens.access_token,
+      access_token: `${this.config.clientId}|${this.config.clientSecret}`,
+    };
+
+    const res = await fetch(`${endpoint}?${new URLSearchParams(data)}`);
+    return await res.json();
+  }
+
+  async getUserProfile(tokens: any) {
+    const inspectResult = await this.inspectToken(tokens);
+    const endpoint = `https://graph.facebook.com/v10.0/${inspectResult.data.user_id}`;
+
+    const data = {
+      access_token: tokens.access_token,
+      fields: this.config.userProfileFields,
+    };
+
+    const res = await fetch(`${endpoint}?${new URLSearchParams(data)}`);
+    return await res.json();
+  }
+}
diff --git a/src/SvelteAuth/providers/google.ts b/src/SvelteAuth/providers/google.ts
new file mode 100644
index 0000000..0f44168
--- /dev/null
+++ b/src/SvelteAuth/providers/google.ts
@@ -0,0 +1,82 @@
+import type { ServerRequest } from "@sveltejs/kit/types/endpoint";
+import { OAuth2Provider, OAuth2ProviderConfig } from "./oauth2";
+
+interface GoogleOAuthProviderConfig extends OAuth2ProviderConfig {
+  clientId: string;
+  clientSecret: string;
+  discoveryDocument?: string;
+  scope?: string;
+}
+
+const defaultConfig: Partial<GoogleOAuthProviderConfig> = {
+  id: "google",
+  discoveryDocument: "https://accounts.google.com/.well-known/openid-configuration",
+  scope: "openid profile email",
+};
+
+export class GoogleOAuthProvider extends OAuth2Provider<GoogleOAuthProviderConfig> {
+  constructor(config: GoogleOAuthProviderConfig) {
+    super({
+      ...defaultConfig,
+      ...config,
+    });
+  }
+
+  async getProviderMetadata() {
+    const res = await fetch(this.config.discoveryDocument);
+    const metadata = await res.json();
+    return metadata;
+  }
+
+  async getEndpoint(key: string) {
+    const metadata = await this.getProviderMetadata();
+    return metadata[key] as string;
+  }
+
+  async getSigninUrl({ host }: ServerRequest, state: string) {
+    const authorizationEndpoint = await this.getEndpoint("authorization_endpoint");
+
+    const data = {
+      response_type: "code",
+      client_id: this.config.clientId,
+      scope: this.config.scope,
+      redirect_uri: this.getCallbackUri(host),
+      state,
+      login_hint: "example@provider.com",
+      nonce: Math.round(Math.random() * 1000).toString(), // TODO: Generate random based on user values
+    };
+
+    const url = `${authorizationEndpoint}?${new URLSearchParams(data)}`;
+    return url;
+  }
+
+  async getTokens(code: string, redirectUri: string) {
+    const tokenEndpoint = await this.getEndpoint("token_endpoint");
+
+    const data = {
+      code,
+      client_id: this.config.clientId,
+      client_secret: this.config.clientSecret,
+      redirect_uri: redirectUri,
+      grant_type: "authorization_code",
+    };
+
+    const res = await fetch(tokenEndpoint, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+      },
+      body: JSON.stringify(data),
+    });
+
+    return await res.json();
+  }
+
+  async getUserProfile(tokens: any) {
+    const userProfileEndpoint = await this.getEndpoint("userinfo_endpoint");
+    const res = await fetch(userProfileEndpoint, {
+      headers: { Authorization: `${tokens.token_type} ${tokens.access_token}` },
+    });
+    return await res.json();
+  }
+}
diff --git a/src/SvelteAuth/providers/index.ts b/src/SvelteAuth/providers/index.ts
new file mode 100644
index 0000000..4e56d7a
--- /dev/null
+++ b/src/SvelteAuth/providers/index.ts
@@ -0,0 +1,2 @@
+export { Provider } from "./base";
+export { GoogleOAuthProvider } from "./google";
diff --git a/src/SvelteAuth/providers/oauth2.ts b/src/SvelteAuth/providers/oauth2.ts
new file mode 100644
index 0000000..16aa1a9
--- /dev/null
+++ b/src/SvelteAuth/providers/oauth2.ts
@@ -0,0 +1,59 @@
+import type { EndpointOutput, ServerRequest } from "@sveltejs/kit/types/endpoint";
+import type { CallbackResult } from "../types";
+import { Provider, ProviderConfig } from "./base";
+
+export interface OAuth2ProviderConfig extends ProviderConfig {
+  profile?: (profile: any, tokens: any) => any | Promise<any>;
+}
+
+export abstract class OAuth2Provider<T extends OAuth2ProviderConfig> extends Provider<T> {
+  abstract getSigninUrl(request: ServerRequest, state: string): string | Promise<string>;
+  abstract getTokens(code: string, redirectUri: string): any | Promise<any>;
+  abstract getUserProfile(tokens: any): any | Promise<any>;
+
+  async signin(request: ServerRequest): Promise<EndpointOutput> {
+    const { method, host, query } = request;
+    const state = [`redirect=${query.get("redirect") ?? this.getUri(host, "/")}`].join(",");
+    const base64State = Buffer.from(state).toString("base64");
+    const url = await this.getSigninUrl(request, base64State);
+
+    if (method === "POST") {
+      return {
+        body: {
+          redirect: url,
+        },
+      };
+    }
+
+    return {
+      status: 302,
+      headers: {
+        Location: url,
+      },
+    };
+  }
+
+  getStateValue(query: URLSearchParams, name: string) {
+    if (query.get("state")) {
+      const state = Buffer.from(query.get("state"), "base64").toString();
+      return state
+        .split(",")
+        .find((state) => state.startsWith(`${name}=`))
+        ?.replace(`${name}=`, "");
+    }
+  }
+
+  async callback({ query, host }: ServerRequest): Promise<CallbackResult> {
+    const code = query.get("code");
+    const redirect = this.getStateValue(query, "redirect");
+
+    const tokens = await this.getTokens(code, this.getCallbackUri(host));
+    let user = await this.getUserProfile(tokens);
+
+    if (this.config.profile) {
+      user = await this.config.profile(user, tokens);
+    }
+
+    return [user, redirect ?? this.getUri(host, "/")];
+  }
+}
diff --git a/src/SvelteAuth/providers/reddit.ts b/src/SvelteAuth/providers/reddit.ts
new file mode 100644
index 0000000..9304f95
--- /dev/null
+++ b/src/SvelteAuth/providers/reddit.ts
@@ -0,0 +1,119 @@
+import type { ServerRequest } from "@sveltejs/kit/types/endpoint";
+import { OAuth2Provider, OAuth2ProviderConfig } from "./oauth2";
+
+interface RedditOAuthProviderConfig extends OAuth2ProviderConfig {
+  apiKey: string;
+  apiSecret: string;
+  scope?: string;
+  duration?: "temporary" | "permanent";
+}
+
+const defaultConfig: Partial<RedditOAuthProviderConfig> = {
+  id: "reddit",
+  scope: "identity",
+  duration: "temporary",
+  profile: ({
+    is_employee,
+    has_external_account,
+    snoovatar_img,
+    verified,
+    id,
+    over_18,
+    is_gold,
+    is_mod,
+    awarder_karma,
+    has_verified_email,
+    is_suspended,
+    icon_img,
+    pref_nightmode,
+    awardee_karma,
+    password_set,
+    link_karma,
+    total_karma,
+    name,
+    created,
+    created_utc,
+    comment_karma,
+  }) => ({
+    is_employee,
+    has_external_account,
+    snoovatar_img,
+    verified,
+    id,
+    over_18,
+    is_gold,
+    is_mod,
+    awarder_karma,
+    has_verified_email,
+    is_suspended,
+    icon_img,
+    pref_nightmode,
+    awardee_karma,
+    password_set,
+    link_karma,
+    total_karma,
+    name,
+    created,
+    created_utc,
+    comment_karma,
+  }),
+};
+
+export class RedditOAuthProvider extends OAuth2Provider<RedditOAuthProviderConfig> {
+  constructor(config: RedditOAuthProviderConfig) {
+    super({
+      ...defaultConfig,
+      ...config,
+    });
+  }
+
+  async getSigninUrl({ host }: ServerRequest, state: string) {
+    const endpoint = "https://www.reddit.com/api/v1/authorize";
+
+    const data = {
+      client_id: this.config.apiKey,
+      response_type: "code",
+      state,
+      redirect_uri: this.getCallbackUri(host),
+      duration: this.config.duration,
+      scope: this.config.scope,
+    };
+
+    const url = `${endpoint}?${new URLSearchParams(data)}`;
+    return url;
+  }
+
+  async getTokens(code: string, redirectUri: string) {
+    const endpoint = "https://www.reddit.com/api/v1/access_token";
+
+    const data = {
+      code,
+      redirect_uri: redirectUri,
+      grant_type: "authorization_code",
+    };
+    const body = Object.entries(data)
+      .map(([key, value]) => `${encodeURIComponent(key)}=${encodeURIComponent(value)}`)
+      .join("&");
+
+    const res = await fetch(endpoint, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/x-www-form-urlencoded",
+        Authorization:
+          "Basic " +
+          Buffer.from(`${this.config.apiKey}:${this.config.apiSecret}`).toString("base64"),
+      },
+      body,
+    });
+
+    return await res.json();
+  }
+
+  async getUserProfile(tokens: any) {
+    const endpoint = "https://oauth.reddit.com/api/v1/me";
+    const res = await fetch(endpoint, {
+      headers: { Authorization: `${tokens.token_type} ${tokens.access_token}` },
+    });
+    return await res.json();
+  }
+}
diff --git a/src/SvelteAuth/providers/twitter.ts b/src/SvelteAuth/providers/twitter.ts
new file mode 100644
index 0000000..934beac
--- /dev/null
+++ b/src/SvelteAuth/providers/twitter.ts
@@ -0,0 +1,87 @@
+import type { ServerRequest } from "@sveltejs/kit/types/endpoint";
+import type { CallbackResult } from "../types";
+import { OAuth2Provider, OAuth2ProviderConfig } from "./oauth2";
+
+interface TwitterAuthProviderConfig extends OAuth2ProviderConfig {
+  apiKey: string;
+  apiSecret: string;
+}
+
+const defaultConfig: Partial<TwitterAuthProviderConfig> = {
+  id: "twitter",
+};
+
+export class TwitterAuthProvider extends OAuth2Provider<TwitterAuthProviderConfig> {
+  constructor(config: TwitterAuthProviderConfig) {
+    super({
+      ...defaultConfig,
+      ...config,
+    });
+  }
+
+  async getRequestToken(host: string) {
+    const endpoint = "https://api.twitter.com/oauth/request_token";
+
+    const data = {
+      oauth_callback: encodeURIComponent(this.getCallbackUri(host)),
+      oauth_consumer_key: this.config.apiKey,
+    };
+
+    const res = await fetch(`${endpoint}?${new URLSearchParams(data)}`, { method: "POST" });
+    const { oauth_token, oauth_token_secret, oauth_callback_confirmed } = await res.json();
+
+    return {
+      oauthToken: oauth_token,
+      oauthTokenSecret: oauth_token_secret,
+      oauthCallbackConfirmed: oauth_callback_confirmed,
+    };
+  }
+
+  async getSigninUrl({ host }: ServerRequest) {
+    const endpoint = "https://api.twitter.com/oauth/authorize";
+
+    const { oauthToken } = await this.getRequestToken(host);
+
+    const data = {
+      oauth_token: oauthToken,
+    };
+
+    const url = `${endpoint}?${new URLSearchParams(data)}`;
+    return url;
+  }
+
+  async getTokens(oauthToken: string, oauthVerifier: string) {
+    const endpoint = "https://api.twitter.com/oauth/access_token";
+
+    const data = {
+      oauth_consumer_key: this.config.apiKey,
+      oauth_token: oauthToken,
+      oauth_verifier: oauthVerifier,
+    };
+
+    const res = await fetch(`${endpoint}?${new URLSearchParams(data)}`, { method: "POST" });
+    return await res.json();
+  }
+
+  async getUserProfile({ oauth_token, oauth_token_secret: _ }: any) {
+    const endpoint = "https://api.twitter.com/1.1/account/verify_credentials.json";
+
+    const res = await fetch(endpoint, { headers: { Authorization: `Bearer ${oauth_token}` } });
+    return await res.json();
+  }
+
+  async callback({ query, host }: ServerRequest): Promise<CallbackResult> {
+    const oauthToken = query.get("oauth_token");
+    const oauthVerifier = query.get("oauth_verifier");
+    const redirect = this.getStateValue(query, "redirect");
+
+    const tokens = await this.getTokens(oauthToken, oauthVerifier);
+    let user = await this.getUserProfile(tokens);
+
+    if (this.config.profile) {
+      user = await this.config.profile(user, tokens);
+    }
+
+    return [user, redirect ?? this.getUri(host, "/")];
+  }
+}
diff --git a/src/SvelteAuth/types.ts b/src/SvelteAuth/types.ts
new file mode 100644
index 0000000..f8fddc4
--- /dev/null
+++ b/src/SvelteAuth/types.ts
@@ -0,0 +1,2 @@
+export type Profile = any;
+export type CallbackResult = [Profile, string | null];