diff --git a/dev/.env.example b/dev/.env.example
index 475d8eb..d18373b 100644
--- a/dev/.env.example
+++ b/dev/.env.example
@@ -22,12 +22,21 @@ NEXT_PUBLIC_URL=http://localhost:3000
 ################################################################################
 # zitadel oauth config
 ################################################################################
-# optional: google oauth2 client id, not activated if not set
+# optional: zitadel oauth2 client id, not activated if not set
 # ZITADEL_CLIENT_ID=
 
-# optional: google oauth2 client secret, not activated if not set
+# optional: zitadel oauth2 client secret, not activated if not set
 # ZITADEL_CLIENT_SECRET=
 
+# optional: zitadel oauth2 token endpoint, not activated if not set
+# ZITADEL_TOKEN_ENDPOINT=
+
+# optional: zitadel oauth2 authorization url, not activated if not set
+# ZITADEL_AUTHORIZATION_URL=
+
+# optional: zitadel oauth2 userinfo endpoint, not activated if not set
+# ZITADEL_USERINFO_ENDPOINT=
+
 ################################################################################
 # Microsoft Entra ID OAuth 2.0 config
 ################################################################################
@@ -43,17 +52,6 @@ NEXT_PUBLIC_URL=http://localhost:3000
 # optional: Microsoft Entra ID administrator group id, activated if not set
 # MICROSOFT_ENTRA_ID_ADMINISTRATOR_GROUP_ID=
 
-# Note: For Microsoft Entra ID, you need to:
-# 1. Create an app registration
-# - Go to Azure Portal -> Microsoft Entra ID -> App Registrations -> New Registration
-# - Fill in the name and select the supported account types
-# - Add a "Web" redirect URI: http://localhost:3000/api/users/oauth/microsoft-entra-id/callback
-# - When created, go to API Permissions -> Add a permission -> Microsoft Graph -> Delegated permissions -> Select the ones you need, e.g. email, openid, profile and offline_access -> Add permissions
-# - Optional: If you do not want users to have to give consent to your app everytime they login: Click on Grant admin consent for {tenant} -> Yes
-# - Optional: If you want groups to be part of your token(s), you can go to Token configuration -> Add groups claim -> Select the groups you want to add -> Save
-# - Go to Certificates & secrets -> Client secrets -> New client secret -> Add a description -> Expires -> Add -> Copy the secret (it will only be shown once) -> And save the secret somewhere safe or add it to your .env file
-# You can read a little about registering apps here as well: https://learn.microsoft.com/en-us/azure/active-directory/develop/quickstart-register-app
-
 ################################################################################
 # Apple OAuth Config
 ################################################################################
@@ -62,12 +60,3 @@ NEXT_PUBLIC_URL=http://localhost:3000
 
 # Optional: Apple OAuth2 Client Secret (Generated from Apple Developer Portal)
 # APPLE_CLIENT_SECRET=your-generated-secret
-
-# Note: For Apple OAuth, you need to:
-# 1. Create an App ID in Apple Developer Portal
-# Quick link: https://developer.apple.com/account/resources/identifiers/bundleId/add/bundle
-# Long instruction
-# 2. Create a Services ID
-# 3. Configure domain association
-# 4. Generate a Client Secret
-# See: https://developer.apple.com/sign-in-with-apple/get-started/
diff --git a/examples/microsoft-entra-id.ts b/examples/microsoft-entra-id.ts
index 9ab969c..7a24a51 100644
--- a/examples/microsoft-entra-id.ts
+++ b/examples/microsoft-entra-id.ts
@@ -16,6 +16,20 @@ const tokenEndpoint = `https://login.microsoftonline.com/${tenantId}/oauth2/v2.0
 const authorizationUrl = `https://login.microsoftonline.com/${tenantId}/oauth2/v2.0/authorize`;
 const microsoftGraphBaseUrl = "https://graph.microsoft.com/v1.0";
 
+/**
+
+Note: For Microsoft Entra ID, you need to xreate an app registration
+  - Go to Azure Portal -> Microsoft Entra ID -> App Registrations -> New Registration
+  - Fill in the name and select the supported account types
+  - Add a "Web" redirect URI: http://localhost:3000/api/users/oauth/microsoft-entra-id/callback
+  - When created, go to API Permissions -> Add a permission -> Microsoft Graph -> Delegated permissions -> Select the ones you need, e.g. email, openid, profile and offline_access -> Add permissions
+  - Optional: If you do not want users to have to give consent to your app everytime they login: Click on Grant admin consent for {tenant} -> Yes
+  - Optional: If you want groups to be part of your token(s), you can go to Token configuration -> Add groups claim -> Select the groups you want to add -> Save
+  - Go to Certificates & secrets -> Client secrets -> New client secret -> Add a description -> Expires -> Add -> Copy the secret (it will only be shown once) -> And save the secret somewhere safe or add it to your .env file
+
+You can read a little about registering apps here as well: https://learn.microsoft.com/en-us/azure/active-directory/develop/quickstart-register-app
+ */
+
 export const microsoftEntraIdOAuth = OAuth2Plugin({
   enabled:
     typeof clientId === "string" &&
diff --git a/package.json b/package.json
index 9486b72..d317b20 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "payload-oauth2",
-  "version": "1.0.16",
+  "version": "1.0.17",
   "type": "module",
   "homepage:": "https://github.com/WilsonLe/payload-oauth2",
   "repository": "https://github.com/WilsonLe/payload-oauth2",
diff --git a/src/callback-endpoint.ts b/src/callback-endpoint.ts
index 4451e27..16139a4 100644
--- a/src/callback-endpoint.ts
+++ b/src/callback-endpoint.ts
@@ -12,6 +12,7 @@ import type {
   User,
 } from "payload";
 import { generatePayloadCookie, getFieldsToSign } from "payload";
+import { defaultCallbackExtractToken } from "./default-callback-extract-token";
 import { defaultGetToken } from "./default-get-token";
 import type { PluginOptions } from "./types";
 
@@ -20,31 +21,6 @@ export const createCallbackEndpoint = (
 ): Endpoint[] => {
   const handler: PayloadHandler = async (req: PayloadRequest) => {
     try {
-      // Obtain code from either POST body or GET query parameters
-      let code: string | undefined;
-      if (req.method === "POST") {
-        // Handle form data from POST request (used by Apple OAuth)
-        const contentType = req.headers.get("content-type");
-        if (contentType?.includes("application/x-www-form-urlencoded")) {
-          const text = await (req as unknown as Request).text();
-          const formData = new URLSearchParams(text);
-          code = formData.get("code") || undefined;
-        }
-      } else if (req.method === "GET") {
-        // Handle query parameters (used by Google OAuth)
-        code =
-          typeof req.query === "object" && req.query
-            ? (req.query as { code?: string }).code
-            : undefined;
-      }
-      if (typeof code !== "string") {
-        throw new Error(
-          `Code not found in ${req.method === "POST" ? "body" : "query"}: ${
-            req.method === "POST" ? "form-data" : JSON.stringify(req.query)
-          }`,
-        );
-      }
-
       // /////////////////////////////////////
       // shorthands
       // /////////////////////////////////////
@@ -61,6 +37,13 @@ export const createCallbackEndpoint = (
         !useEmailAsIdentity || pluginOptions.excludeEmailFromJwtToken || false;
       const onUserNotFoundBehavior =
         pluginOptions.onUserNotFoundBehavior || "create";
+      const callbackExtractToken =
+        pluginOptions.callbackExtractToken || defaultCallbackExtractToken;
+
+      // /////////////////////////////////////
+      // extract code from request
+      // /////////////////////////////////////
+      const code = await callbackExtractToken(req);
 
       // /////////////////////////////////////
       // beforeOperation - Collection
diff --git a/src/default-callback-extract-token.ts b/src/default-callback-extract-token.ts
new file mode 100644
index 0000000..4bd3563
--- /dev/null
+++ b/src/default-callback-extract-token.ts
@@ -0,0 +1,45 @@
+import { PayloadRequest } from "payload";
+
+export const defaultCallbackExtractToken = async (
+  req: PayloadRequest,
+): Promise<string> => {
+  if (req.method === "POST") {
+    // Handle form data from POST request (used by Apple OAuth)
+    const contentType = req.headers.get("content-type");
+    if (contentType?.includes("application/x-www-form-urlencoded")) {
+      const text = await (req as unknown as Request).text();
+      const formData = new URLSearchParams(text);
+      const code = formData.get("code");
+      if (typeof code === "string") {
+        return code;
+      } else {
+        throw new Error(`Code not found in POST form data: ${text}`);
+      }
+    } else if (contentType?.includes("application/json")) {
+      if (typeof req.json === "function") {
+        const body = await req.json();
+        if (typeof body.code === "string") {
+          return body.code;
+        } else {
+          throw new Error(
+            `Code not found in POST request body: ${JSON.stringify(body)}`,
+          );
+        }
+      }
+    } else {
+      throw new Error(
+        `Unsupported content-type: ${contentType} received in POST callback endpoint`,
+      );
+    }
+  } else if (req.method === "GET") {
+    // Handle query parameters (used by Google OAuth)
+    if (typeof req.query === "object" && typeof req.query.code === "string") {
+      return req.query.code;
+    } else {
+      throw new Error(
+        `Code not found in GET request query param: ${JSON.stringify(req.query)}`,
+      );
+    }
+  }
+  throw new Error("Authorization code not found in callback request");
+};
diff --git a/src/default-get-token.ts b/src/default-get-token.ts
index 88c88c9..f0c626c 100644
--- a/src/default-get-token.ts
+++ b/src/default-get-token.ts
@@ -22,6 +22,6 @@ export const defaultGetToken = async (
   const tokenData = await tokenResponse.json();
   const accessToken = tokenData?.access_token;
   if (typeof accessToken !== "string")
-    throw new Error(`No access token: ${tokenData}`);
+    throw new Error(`No access token: ${JSON.stringify(tokenData)}`);
   return accessToken;
 };
diff --git a/src/types.ts b/src/types.ts
index 147284d..c04a41d 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -113,6 +113,14 @@ export interface PluginOptions {
     req: PayloadRequest,
   ) => Promise<Record<string, unknown>>;
 
+  /**
+   * Function to extract authorization code from the callback request.
+   * @param req PayloadRequest object
+   * @returns Promise that resolves to the authorization code
+   * @default `defaultCallbackExtractToken` in `src/default-callback-extract-token.ts`
+   */
+  callbackExtractToken?: (req: PayloadRequest) => Promise<string>;
+
   /**
    * Behavior when a user is not found in the database.
    * If set to "create", a new user will be created with the information