diff --git a/content/cors-errors/index.md b/content/cors-errors/index.md
new file mode 100644
index 00000000..309ce5df
--- /dev/null
+++ b/content/cors-errors/index.md
@@ -0,0 +1,916 @@
+---
+title: Fixing CORS Errors What They Are and How to Resolve Them
+description: "Learn what causes CORS errors, how they impact your web app, and how to fix them securely with proper headers and backend configurations."
+date: "2025-07-20"
+cover: "cors_errors.png"
+category: "cors errors, development tips, best practices"
+author: "Maurice Saldivar"
+---
+
+# Fixing CORS Errors: What They Are and How to Resolve Them
+A comprehensive guide to learning how to find, debug, and fix CORS errors in your web applications.
+
+## What Is a CORS Error and Why Does It Happen?
+
+CORS errors are one of the most common stumbling blocks in modern web development. Your API works perfectly in Postman, but the moment you try to fetch data from your frontend, the browser blocks the request with a cryptic error message.
+
+### Definition of CORS
+
+Cross-Origin Resource Sharing (CORS) is a browser security mechanism that controls whether JavaScript running on one website can access resources from another website. It extends the Same-Origin Policy, which serves as the browser's fundamental trust boundary.
+
+An origin consists of three parts:
+
+- **Protocol**: `http://` vs `https://`
+- **Domain**: `example.com` vs `api.example.com`
+- **Port**: `:3000` vs `:8080`
+
+Any difference in these components triggers a cross-origin request, which requires explicit permission from the server.
+
+```javascript
+// Same origin requests 
+fetch('/api/users')                          // Relative URL
+fetch('https://myapp.com/api/data')         // Same protocol, domain, port
+
+// Cross-origin requests
+fetch('https://api.myapp.com/users')        // Different subdomain
+fetch('http://myapp.com/api/users')         // Different protocol  
+fetch('https://myapp.com:8080/api/users')   // Different port
+```
+
+The Same-Origin Policy exists to prevent malicious websites from reading sensitive data from other sites. Without it, any website could access your Gmail, initiate bank transfers, or steal session tokens.
+
+### What Triggers a CORS Error?
+
+A CORS error occurs when your browser blocks a response because the server didn't include the required permission headers. Here's the typical sequence:
+
+1. Your frontend at `http://localhost:3000` makes a request to `https://api.yourservice.com`
+2. The browser detects a cross-origin request
+3. The request is sent to the server
+4. The server responds without CORS headers
+5. The browser blocks JavaScript from accessing the response
+6. A CORS error appears in the console
+
+The crucial detail: the request often completes successfully on the server. CORS doesn't prevent the request, it prevents your JavaScript from reading the response. This distinction matters when debugging issues like duplicate database entries despite console errors.
+
+### CORS Preflight and Actual Requests
+
+Browsers categorize HTTP requests into two types for CORS purposes:
+
+**Simple Requests** proceed without preflight:
+- GET, HEAD, or POST methods
+- Limited headers (Accept, Content-Language, Content-Type with restrictions)
+- Content-Type must be `application/x-www-form-urlencoded`, `multipart/form-data`, or `text/plain`
+
+**Preflighted Requests** require permission first:
+- Any other HTTP method (PUT, DELETE, PATCH)
+- Custom headers like `Authorization` or `X-API-Key`
+- POST with `Content-Type: application/json`
+
+Here's the preflight flow:
+
+```bash
+# Browser sends preflight
+OPTIONS /api/users HTTP/1.1
+Origin: http://localhost:3000
+Access-Control-Request-Method: POST
+Access-Control-Request-Headers: Content-Type, Authorization
+
+# Server responds with permissions
+HTTP/1.1 204 No Content
+Access-Control-Allow-Origin: http://localhost:3000
+Access-Control-Allow-Methods: POST, GET, OPTIONS
+Access-Control-Allow-Headers: Content-Type, Authorization
+
+# Browser sends actual request
+POST /api/users HTTP/1.1
+Origin: http://localhost:3000
+Authorization: Bearer your-token-here
+Content-Type: application/json
+
+{"name": "New User"}
+
+# Server includes CORS headers with response
+HTTP/1.1 201 Created
+Access-Control-Allow-Origin: http://localhost:3000
+
+{"id": 123, "name": "New User"}
+```
+
+This preflight process explains why JSON API calls appear slower in browsers than in Postman, browsers must complete the permission check first, while Postman skips CORS entirely.
+
+## Common Types of CORS Errors and Their Meaning
+
+### No "Access-Control-Allow-Origin" header
+
+This error means the server didn't include the header that authorizes your origin to access the response.
+
+```javascript
+fetch('https://api.coolservice.com/data')
+  .then(res => res.json())
+  .then(data => console.log(data))
+
+// Error:
+// Access to fetch at 'https://api.coolservice.com/data' from origin 
+// 'http://localhost:3000' has been blocked by CORS policy: 
+// No 'Access-Control-Allow-Origin' header is present on the requested resource.
+```
+
+The server processed your request but didn't include the required header. Your browser discards the response before JavaScript can access it.
+
+For servers you control:
+
+```javascript
+app.use((req, res, next) => {
+  res.header('Access-Control-Allow-Origin', 'http://localhost:3000');
+  next();
+});
+```
+
+For external APIs, you'll need a proxy server or the API must support CORS.
+
+### "Method not allowed by Access-Control-Allow-Methods"
+
+The server accepts some HTTP methods but not the one you're using.
+
+```javascript
+fetch('https://api.example.com/users/123', {
+  method: 'DELETE',
+  headers: {
+    'Authorization': 'Bearer token'
+  }
+})
+
+// Error:
+// Method DELETE is not allowed by Access-Control-Allow-Methods in preflight response.
+```
+
+This occurs during preflight when the server's `Access-Control-Allow-Methods` header doesn't include your method. Common causes include missing OPTIONS endpoints or incomplete method lists.
+
+### "Credentialed requests not supported"
+
+This error appears when sending cookies or authentication headers cross-origin with incorrect server configuration.
+
+```javascript
+fetch('https://api.example.com/profile', {
+  credentials: 'include'
+})
+
+// Error:
+// The value of the 'Access-Control-Allow-Origin' header in the response 
+// must not be the wildcard '*' when the request's credentials mode is 'include'.
+```
+
+Credentialed requests require:
+- Specific origin (not wildcard)
+- `Access-Control-Allow-Credentials: true`
+
+```javascript
+res.header('Access-Control-Allow-Origin', 'http://localhost:3000');
+res.header('Access-Control-Allow-Credentials', 'true');
+```
+
+### CORS Errors in Fetch vs. Axios
+
+Fetch and Axios handle CORS differently:
+
+```javascript
+// Fetch - generic error messages
+fetch('https://api.example.com/data')
+  .catch(error => {
+    console.log(error.message);  // "Failed to fetch"
+  });
+
+// Axios - more detailed error handling
+axios.get('https://api.example.com/data')
+  .catch(error => {
+    if (error.response) {
+      console.log('Server responded with error:', error.response.status);
+    } else if (error.request) {
+      console.log('No response received:', error.message);
+    }
+  });
+```
+
+Key differences:
+1. Fetch provides generic "Failed to fetch" for network errors including CORS
+2. Axios automatically sets `Content-Type: application/json`, triggering preflight
+3. Axios interceptors can add headers that unexpectedly trigger preflight
+
+## How to Fix CORS Errors (Frontend & Backend)
+
+CORS is fundamentally a server-side configuration. Frontend workarounds exist for development, but production requires proper backend setup.
+
+### Set Proper Headers on the Server:
+
+**Access-Control-Allow-Origin**
+
+```javascript
+// Development
+res.header('Access-Control-Allow-Origin', 'http://localhost:3000');
+
+// Production with multiple origins
+const allowedOrigins = ['https://app.example.com', 'https://beta.example.com'];
+const origin = req.headers.origin;
+if (allowedOrigins.includes(origin)) {
+  res.header('Access-Control-Allow-Origin', origin);
+}
+```
+
+**Access-Control-Allow-Methods**
+
+```javascript
+res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
+```
+
+**Access-Control-Allow-Headers**
+
+```javascript
+res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization, X-API-Key');
+```
+
+**Access-Control-Allow-Credentials**
+
+```javascript
+res.header('Access-Control-Allow-Credentials', 'true');
+```
+
+**Access-Control-Max-Age**
+
+```javascript
+res.header('Access-Control-Max-Age', '86400');
+```
+
+### Enable CORS in Node.js/Express
+
+
+```javascript
+const cors = require('cors');
+
+const corsOptions = {
+  origin: function (origin, callback) {
+    const allowedOrigins = [
+      'https://app.example.com',
+      'https://admin.example.com',
+      'http://localhost:3000'
+    ];
+    
+    if (!origin) return callback(null, true);
+    
+    if (allowedOrigins.indexOf(origin) !== -1) {
+      callback(null, true);
+    } else {
+      callback(new Error('Not allowed by CORS'));
+    }
+  },
+  credentials: true,
+  methods: ['GET', 'POST', 'PUT', 'DELETE', 'OPTIONS'],
+  allowedHeaders: ['Content-Type', 'Authorization'],
+  maxAge: 86400
+};
+
+app.use(cors(corsOptions));
+app.options('*', cors(corsOptions));
+```
+
+
+### Configuring CORS in Other Backends
+
+### Flask
+
+```python
+from flask import Flask, jsonify, request
+from flask_cors import CORS
+
+app = Flask(__name__)
+
+CORS(app, origins=["https://app.example.com"], supports_credentials=True)
+
+@app.after_request
+def after_request(response):
+    origin = request.headers.get('Origin')
+    if origin in ['https://app.example.com', 'http://localhost:3000']:
+        response.headers['Access-Control-Allow-Origin'] = origin
+        response.headers['Access-Control-Allow-Credentials'] = 'true'
+        response.headers['Access-Control-Allow-Methods'] = 'GET, POST, PUT, DELETE'
+        response.headers['Access-Control-Allow-Headers'] = 'Content-Type, Authorization'
+    return response
+```
+
+### Django
+
+```python
+# settings.py
+INSTALLED_APPS = [
+    'corsheaders',
+]
+
+MIDDLEWARE = [
+    'corsheaders.middleware.CorsMiddleware',
+    'django.middleware.common.CommonMiddleware',
+]
+
+CORS_ALLOWED_ORIGINS = [
+    "http://localhost:3000",
+    "https://app.example.com",
+]
+
+CORS_ALLOW_CREDENTIALS = True
+
+CORS_ALLOW_HEADERS = [
+    'accept',
+    'authorization',
+    'content-type',
+    'x-csrftoken',
+]
+```
+
+### Spring Boot
+
+```java
+@Configuration
+@EnableWebMvc
+public class WebConfig implements WebMvcConfigurer {
+
+    @Override
+    public void addCorsMappings(CorsRegistry registry) {
+        registry.addMapping("/api/**")
+            .allowedOrigins("https://app.example.com", "http://localhost:3000")
+            .allowedMethods("GET", "POST", "PUT", "DELETE", "OPTIONS")
+            .allowedHeaders("Content-Type", "Authorization")
+            .allowCredentials(true)
+            .maxAge(3600);
+    }
+}
+```
+
+### Frontend Considerations
+
+What doesn't work, adding CORS headers to fetch requests has no effect:
+
+```javascript
+fetch('https://api.example.com/data', {
+  headers: {
+    'Access-Control-Allow-Origin': '*',
+  }
+})
+```
+
+The `no-cors` mode prevents reading responses:
+
+```javascript
+fetch('https://api.example.com/data', {
+  mode: 'no-cors'
+})
+.then(response => response.json())
+```
+
+What actually works, using a proxy during development:
+
+```javascript
+// Vite config
+export default {
+  server: {
+    proxy: {
+      '/api': {
+        target: 'https://api.example.com',
+        changeOrigin: true,
+        rewrite: (path) => path.replace(/^\/api/, '')
+      }
+    }
+  }
+}
+```
+
+Ensure correct request configuration:
+
+```javascript
+fetch('https://api.example.com/data', {
+  method: 'POST',
+  headers: {
+    'Content-Type': 'application/json'
+  },
+  body: JSON.stringify(data)
+})
+```
+
+## SuperTokens and CORS Configuration
+
+Authentication adds complexity to CORS because credentials require stricter security rules. SuperTokens simplifies most of this, but understanding the underlying mechanics prevents configuration issues.
+
+### Why CORS Matters for Auth Flows
+
+SuperTokens uses httpOnly cookies for session management, which immediately impacts CORS requirements:
+
+```javascript
+fetch('https://api.example.com/auth/session/verify', {
+  method: 'GET',
+  credentials: 'include'
+})
+```
+
+With credentials, CORS rules become stricter:
+- No wildcard origins allowed
+- `Access-Control-Allow-Credentials` must be `true`
+- Origins must match exactly
+
+### Authentication Headers Trigger Preflight
+
+```javascript
+fetch('https://api.example.com/auth/signin', {
+  method: 'POST',
+  headers: {
+    'Content-Type': 'application/json',
+    'rid': 'emailpassword',
+    'st-auth-mode': 'cookie'
+  },
+  credentials: 'include',
+  body: JSON.stringify({ email, password })
+})
+```
+
+### How SuperTokens Handles CORS
+
+SuperTokens automatically manages CORS for its authentication endpoints:
+
+```javascript
+import supertokens from "supertokens-node";
+import Session from "supertokens-node/recipe/session";
+
+supertokens.init({
+  framework: "express",
+  supertokens: {
+    connectionURI: "https://try.supertokens.com",
+  },
+  appInfo: {
+    appName: "MyApp",
+    apiDomain: "https://api.example.com",
+    websiteDomain: "https://app.example.com",
+    apiBasePath: "/auth",
+    websiteBasePath: "/auth"
+  },
+  recipeList: [
+    Session.init({
+      cookieSameSite: "none",
+      cookieSecure: true,
+    })
+  ]
+});
+```
+
+SuperTokens derives CORS settings from `appInfo`, but only for its own routes. Your API endpoints need separate configuration.
+
+### Common CORS Pitfalls with SuperTokens
+
+Mismatched Domains:
+
+```javascript
+supertokens.init({
+  appInfo: {
+    apiDomain: "http://localhost:8080",
+    websiteDomain: "http://localhost:3000"
+  }
+});
+```
+
+Cookie Configuration:
+
+```javascript
+Session.init({
+  cookieSameSite: process.env.NODE_ENV === "production" ? "none" : "lax",
+  cookieSecure: process.env.NODE_ENV === "production"
+})
+```
+
+API Route Configuration:
+
+```javascript
+app.use(cors({
+  origin: ["https://app.example.com", "http://localhost:3000"],
+  credentials: true
+}));
+```
+
+## Secure Implementation Example
+
+Express Setup:
+
+```javascript
+import express from 'express';
+import cors from 'cors';
+import supertokens from "supertokens-node";
+import Session from "supertokens-node/recipe/session";
+import { middleware, errorHandler } from "supertokens-node/framework/express";
+
+const app = express();
+
+const apiDomain = process.env.API_DOMAIN || "http://localhost:8080";
+const websiteDomain = process.env.WEBSITE_DOMAIN || "http://localhost:3000";
+const isProduction = process.env.NODE_ENV === "production";
+
+supertokens.init({
+  framework: "express",
+  supertokens: {
+    connectionURI: process.env.SUPERTOKENS_CONNECTION_URI,
+    apiKey: process.env.SUPERTOKENS_API_KEY,
+  },
+  appInfo: {
+    appName: "MySecureApp",
+    apiDomain,
+    websiteDomain,
+    apiBasePath: "/auth",
+    websiteBasePath: "/auth"
+  },
+  recipeList: [
+    Session.init({
+      cookieSameSite: isProduction ? "none" : "lax",
+      cookieSecure: isProduction,
+      antiCsrf: "VIA_TOKEN",
+    })
+  ]
+});
+
+const corsOptions = {
+  origin: function (origin, callback) {
+    const allowedOrigins = [websiteDomain];
+    if (!origin || allowedOrigins.includes(origin)) {
+      callback(null, true);
+    } else {
+      callback(new Error('Not allowed by CORS'));
+    }
+  },
+  credentials: true,
+  methods: ['GET', 'PUT', 'POST', 'DELETE', 'OPTIONS'],
+  allowedHeaders: ['Content-Type', 'Authorization', 'rid', 'st-auth-mode'],
+};
+
+app.use(cors(corsOptions));
+app.use(middleware());
+
+app.get('/api/user/profile', 
+  Session.verifySession(),
+  async (req, res) => {
+    const userId = req.session.getUserId();
+    res.json({ userId, profile: "..." });
+  }
+);
+
+app.use(errorHandler());
+```
+
+Frontend Configuration:
+
+```javascript
+import SuperTokens from "supertokens-auth-react";
+import Session from "supertokens-auth-react/recipe/session";
+
+SuperTokens.init({
+  appInfo: {
+    appName: "MyApp",
+    apiDomain: "http://localhost:8080",
+    websiteDomain: "http://localhost:3000",
+    apiBasePath: "/auth",
+    websiteBasePath: "/auth"
+  },
+  recipeList: [Session.init()]
+});
+
+async function fetchUserData() {
+  const response = await fetch(`${API_URL}/user/profile`, {
+    method: 'GET',
+    credentials: 'include',
+    headers: { 'Content-Type': 'application/json' }
+  });
+  return response.json();
+}
+```
+
+## Best Practices for Secure CORS Handling
+
+### Avoid Wildcard Origins in Production
+
+Using `Access-Control-Allow-Origin: *` in production eliminates the security benefits of CORS.
+
+```javascript
+const allowedOrigins = {
+  production: ['https://app.yourcompany.com', 'https://www.yourcompany.com'],
+  staging: ['https://staging.yourcompany.com'],
+  development: ['http://localhost:3000', 'http://localhost:3001']
+};
+
+const corsOptions = {
+  origin: function (origin, callback) {
+    const env = process.env.NODE_ENV || 'development';
+    const allowed = allowedOrigins[env];
+    
+    if (!origin) return callback(null, true);
+    
+    if (allowed.includes(origin)) {
+      callback(null, true);
+    } else {
+      console.error(`CORS rejected origin: ${origin}`);
+      callback(new Error('CORS policy violation'));
+    }
+  }
+};
+```
+
+Exception: truly public, read-only APIs can use wildcards:
+
+```javascript
+app.get('/api/public/weather', cors({ origin: '*' }), (req, res) => {
+  res.json({ temperature: 72, conditions: 'sunny' });
+});
+```
+
+### Control Credentials Carefully
+
+Credentials enforce stricter CORS rules:
+
+```javascript
+const corsOptions = {
+  origin: function (origin, callback) {
+    const allowedOrigins = process.env.ALLOWED_ORIGINS?.split(',') || [];
+    
+    if (!origin || allowedOrigins.includes(origin)) {
+      callback(null, true);
+    } else {
+      callback(new Error('Not allowed by CORS'));
+    }
+  },
+  credentials: true,
+  allowedHeaders: ['Content-Type', 'Authorization'],
+  methods: ['GET', 'POST'],
+  exposedHeaders: ['X-Total-Count']
+};
+
+const cookieConfig = {
+  httpOnly: true,
+  secure: process.env.NODE_ENV === 'production',
+  sameSite: process.env.NODE_ENV === 'production' ? 'none' : 'lax',
+  domain: process.env.NODE_ENV === 'production' ? '.example.com' : undefined
+};
+```
+
+### Whitelist Only Necessary Origins
+
+```javascript
+class CORSWhitelist {
+  constructor() {
+    this.origins = new Map([
+      ['production', new Set([
+        'https://app.example.com',
+        'https://www.example.com'
+      ])],
+      ['staging', new Set([
+        'https://staging.example.com'
+      ])],
+      ['development', new Set([
+        'http://localhost:3000'
+      ])]
+    ]);
+  }
+
+  isAllowed(origin, environment = process.env.NODE_ENV) {
+    const allowedForEnv = this.origins.get(environment);
+    return allowedForEnv ? allowedForEnv.has(origin) : false;
+  }
+}
+
+const whitelist = new CORSWhitelist();
+
+app.use(cors({
+  origin: (origin, callback) => {
+    if (!origin || whitelist.isAllowed(origin)) {
+      callback(null, true);
+    } else {
+      callback(new Error(`Origin ${origin} not allowed by CORS`));
+    }
+  }
+}));
+```
+
+### Monitor Preflight Requests
+
+```javascript
+app.options('*', (req, res, next) => {
+  const preflightData = {
+    timestamp: new Date().toISOString(),
+    origin: req.headers.origin || 'no-origin',
+    method: req.headers['access-control-request-method'],
+    headers: req.headers['access-control-request-headers'],
+    path: req.path
+  };
+  
+  if (!req.headers.origin) {
+    console.info('Preflight without origin:', preflightData);
+  } else if (!whitelist.isAllowed(req.headers.origin)) {
+    console.warn('Rejected preflight:', preflightData);
+  }
+  
+  next();
+});
+```
+
+## Debugging CORS Issues in Production
+
+Production CORS issues often stem from infrastructure rather than application code. The browser's Network tab provides crucial debugging information.
+
+### Using Browser Developer Tools
+
+The Network tab reveals the complete request/response cycle:
+
+```bash
+# Healthy CORS flow
+OPTIONS /api/users     204    2ms    (preflight)
+POST    /api/users     201    45ms   (actual request)
+
+# Failed CORS flow
+POST    /api/users     ---    0ms    (CORS error - no preflight)
+```
+
+Key indicators to check:
+1. Missing OPTIONS requests indicate server preflight handling issues
+2. Response headers show what CORS headers the server actually sent
+3. Timing information reveals if responses were received but blocked
+
+### Server Log Analysis
+
+```bash
+# Healthy preflight
+[2024-01-15 14:23:45] OPTIONS /api/users 204 2ms
+[2024-01-15 14:23:45] POST /api/users 201 45ms
+
+# Common production issues
+[2024-01-15 14:23:45] POST /api/users 500 "Method not allowed"
+[2024-01-15 14:23:45] OPTIONS /api/users 401 "Unauthorized"
+```
+
+Enhanced logging for debugging:
+
+```javascript
+app.use((req, res, next) => {
+  if (req.method === 'OPTIONS' || req.headers.origin) {
+    console.log('[CORS Debug]', {
+      timestamp: new Date().toISOString(),
+      method: req.method,
+      path: req.path,
+      origin: req.headers.origin,
+      headers: {
+        'access-control-request-method': req.headers['access-control-request-method'],
+        'access-control-request-headers': req.headers['access-control-request-headers'],
+      }
+    });
+  }
+  next();
+});
+```
+
+### Testing Tools
+
+Test actual browser behavior with curl:
+
+```bash
+# Simulate preflight
+curl -X OPTIONS https://api.production.com/users \
+  -H "Origin: https://app.production.com" \
+  -H "Access-Control-Request-Method: POST" \
+  -H "Access-Control-Request-Headers: Content-Type, Authorization" \
+  -v
+
+# Look for these headers in response
+< access-control-allow-origin: https://app.production.com
+< access-control-allow-methods: GET, POST, PUT, DELETE, OPTIONS
+< access-control-allow-headers: content-type, authorization
+```
+
+Common production-specific issues:
+- CDNs stripping CORS headers
+- Load balancers blocking OPTIONS
+- Reverse proxies changing paths
+- Missing environment variables
+
+## Summary and Developer Checklist
+
+### Core CORS Principles
+
+1. **CORS is server-configured** - Frontend workarounds don't fix production issues
+2. **Credentials change the rules** - No wildcards, explicit origins required
+3. **Infrastructure matters** - CDNs, load balancers, and proxies affect CORS
+4. **Preflight is critical** - OPTIONS must work for complex requests
+
+### Developer CORS Checklist
+
+#### Server Headers
+```javascript
+res.header('Access-Control-Allow-Origin', 'https://app.example.com');
+res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
+res.header('Access-Control-Allow-Headers', 'Content-Type, Authorization');
+res.header('Access-Control-Allow-Credentials', 'true');
+res.header('Access-Control-Max-Age', '86400');
+```
+
+#### Origin Configuration
+```javascript
+const ALLOWED_ORIGINS = {
+  development: ['http://localhost:3000'],
+  staging: ['https://staging.example.com'],
+  production: ['https://app.example.com']
+};
+
+function getAllowedOrigin(req) {
+  const origin = req.headers.origin;
+  const env = process.env.NODE_ENV || 'development';
+  const allowedOrigins = ALLOWED_ORIGINS[env] || [];
+  
+  if (!origin) return '*';
+  if (allowedOrigins.includes(origin)) return origin;
+  
+  console.warn(`CORS: Rejected origin ${origin}`);
+  return false;
+}
+```
+
+#### Credential Handling
+```javascript
+// Frontend
+fetch(url, { credentials: 'include' });
+
+// Backend
+res.header('Access-Control-Allow-Credentials', 'true');
+res.header('Access-Control-Allow-Origin', specificOrigin);
+
+// Cookies
+res.cookie('session', token, {
+  httpOnly: true,
+  secure: true,
+  sameSite: 'none'
+});
+```
+
+#### Preflight Handling
+```javascript
+app.options('*', (req, res) => {
+  res.header('Access-Control-Allow-Origin', getAllowedOrigin(req));
+  res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE, OPTIONS');
+  res.header('Access-Control-Allow-Headers', req.headers['access-control-request-headers']);
+  res.header('Access-Control-Max-Age', '86400');
+  
+  res.sendStatus(204);
+});
+```
+
+### Production Deployment Verification
+
+```bash
+#!/bin/bash
+# CORS verification script
+
+API_DOMAIN="https://api.example.com"
+FRONTEND_DOMAIN="https://app.example.com"
+
+# Test preflight
+echo "Testing preflight..."
+curl -s -X OPTIONS "$API_DOMAIN/api/test" \
+  -H "Origin: $FRONTEND_DOMAIN" \
+  -H "Access-Control-Request-Method: POST" \
+  -I | grep -i "access-control"
+
+# Test actual request
+echo "Testing actual request..."
+curl -s -X GET "$API_DOMAIN/api/health" \
+  -H "Origin: $FRONTEND_DOMAIN" \
+  -I | grep -i "access-control"
+```
+
+### Emergency Production Fix
+
+When production fails and you need immediate resolution:
+
+```javascript
+app.use((req, res, next) => {
+  console.warn('EMERGENCY CORS MODE - TEMPORARY ONLY');
+  
+  res.header('Access-Control-Allow-Origin', req.headers.origin || '*');
+  res.header('Access-Control-Allow-Methods', '*');
+  res.header('Access-Control-Allow-Headers', '*');
+  res.header('Access-Control-Allow-Credentials', 'true');
+  
+  if (req.method === 'OPTIONS') {
+    return res.sendStatus(204);
+  }
+  
+  next();
+});
+```
+
+Then gradually restrict based on actual requirements.
+
+### Final Recommendations
+
+- Test CORS configuration early in development
+- Log CORS requests and rejections in production
+- Understand your infrastructure's impact on headers
+- Use specific origins instead of wildcards
+- Keep authentication flows simple to minimize CORS complexity
+
+With proper understanding and configuration, CORS becomes a powerful security ally rather than a development obstacle.
\ No newline at end of file
diff --git a/static/blog-seo/config.json b/static/blog-seo/config.json
index 1351ab6d..ad32aca6 100644
--- a/static/blog-seo/config.json
+++ b/static/blog-seo/config.json
@@ -3346,7 +3346,7 @@
         "title": "What Is Ping Identity and How Does It Compare?",
         "schema": "<script type=\"application/ld+json\"> {\n            \"@context\": \"https://schema.org\",\n            \"@type\": \"Article\",\n            \"mainEntityOfPage\": {\n                \"@type\": \"WebPage\",\n                \"@id\": \"https://supertokens.com/blog/ping-identity\"\n            },\n            \"headline\": \"Compare Ping Identity to Okta, ForgeRock, OneLogin & SuperTokens. Honest feature breakdowns, use cases, and authentication strengths.\",\n            \"image\": \"https://supertokens.com/blog-meta-images/what-is-ping-identity-and-how-does-it-compare.png\",\n            \"author\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"url\": \"https://supertokens.com\"\n            },\n            \"publisher\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"logo\": {\n                    \"@type\": \"ImageObject\",\n                    \"url\": \"https://supertokens.com/static/assets/dark-home/logo.png\"\n                }\n            }\n        }</script>"
     },
-    { 
+    {
         "path": "/blog/auth-saas",
         "metaTags": [
             "<meta name=\"description\" content=\"Discover how Auth SaaS (Authentication as a Service) simplifies user authentication, enhances security, and scales with your application's needs.\" />",
@@ -3369,7 +3369,7 @@
         "title": "What is Auth SaaS (Authentication as a Service)?",
         "schema": "<script type=\"application/ld+json\"> {\n            \"@context\": \"https://schema.org\",\n            \"@type\": \"Article\",\n            \"mainEntityOfPage\": {\n                \"@type\": \"WebPage\",\n                \"@id\": \"https://supertokens.com/blog/auth-saas\"\n            },\n            \"headline\": \"Discover how Auth SaaS (Authentication as a Service) simplifies user authentication, enhances security, and scales with your application's needs.\",\n            \"image\": \"https://supertokens.com/blog-meta-images/what-is-auth-saas-(authentication-as-a-service).png\",\n            \"author\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"url\": \"https://supertokens.com\"\n            },\n            \"publisher\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"logo\": {\n                    \"@type\": \"ImageObject\",\n                    \"url\": \"https://supertokens.com/static/assets/dark-home/logo.png\"\n                }\n            }\n        }</script>"
     },
-    {    
+    {
         "path": "/blog/top-auth0-alternatives-in-2025",
         "metaTags": [
             "<meta name=\"description\" content=\"Explore the top Auth0 alternatives for authentication and authorization. Discover solutions like SuperTokens, Okta, and Keycloak to find the perfect fit for your business needs.\" />",
@@ -4196,5 +4196,28 @@
         ],
         "title": "SuperTokens Launch Week: Recap",
         "schema": "<script type=\"application/ld+json\"> {\n            \"@context\": \"https://schema.org\",\n            \"@type\": \"Article\",\n            \"mainEntityOfPage\": {\n                \"@type\": \"WebPage\",\n                \"@id\": \"https://supertokens.com/blog/launch-week-1-recap\"\n            },\n            \"headline\": \"With SuperTokens launch week 1 behind us, let's take a look at everything we've announced.\",\n            \"image\": \"https://supertokens.com/blog-meta-images/launch-week-recap.png\",\n            \"author\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"url\": \"https://supertokens.com\"\n            },\n            \"publisher\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"logo\": {\n                    \"@type\": \"ImageObject\",\n                    \"url\": \"https://supertokens.com/static/assets/dark-home/logo.png\"\n                }\n            }\n        }</script>"
+    },
+    {
+        "path": "/blog/cors-errors",
+        "metaTags": [
+            "<meta name=\"description\" content=\"Learn what causes CORS errors, how they impact your web app, and how to fix them securely with proper headers and backend configurations.\" />",
+            "",
+            "<meta name=\"keywords\" content=\"Authentication, Open Source, Authorization, User Management, OAuth, Enterprise SSO, Security\" />",
+            "<!--OG Tags-->",
+            "<meta property=\"og:title\" content=\"Fixing CORS Errors What They Are and How to Resolve Them\" />",
+            "<meta property=\"og:type\" content=\"article\" />",
+            "<meta property=\"og:url\" content=\"https://supertokens.com/blog/cors-errors\" />",
+            "<meta property=\"og:description\" content=\"Learn what causes CORS errors, how they impact your web app, and how to fix them securely with proper headers and backend configurations.\"/>",
+            "<meta property=\"og:image\" content=\"https://supertokens.com/blog-meta-images/cors_errors.png\" />",
+            "",
+            "<meta name=\"twitter:card\" content=\"summary_large_image\" />",
+            "<meta name=\"twitter:title\" content=\"Learn what causes CORS errors, how they impact your web app, and how to fix them securely with proper headers and backend configurations.\" />",
+            "<meta name=\"twitter:url\" content=\"https://supertokens.com/blog/cors-errors\" />",
+            "<meta name=\"twitter:image\" content=\"https://supertokens.com/blog-meta-images/cors_errors.png\" /> ",
+            "<!--OG Tags-->",
+            "<link rel=\"canonical\" href=\"https://supertokens.com/blog/cors-errors\">"
+        ],
+        "title": "Fixing CORS Errors What They Are and How to Resolve Them",
+        "schema": "<script type=\"application/ld+json\"> {\n            \"@context\": \"https://schema.org\",\n            \"@type\": \"Article\",\n            \"mainEntityOfPage\": {\n                \"@type\": \"WebPage\",\n                \"@id\": \"https://supertokens.com/blog/cors-errors\"\n            },\n            \"headline\": \"Learn what causes CORS errors, how they impact your web app, and how to fix them securely with proper headers and backend configurations.\",\n            \"image\": \"https://supertokens.com/blog-meta-images/cors_errors.png\",\n            \"author\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"url\": \"https://supertokens.com\"\n            },\n            \"publisher\": {\n                \"@type\": \"Organization\",\n                \"name\": \"SuperTokens\",\n                \"logo\": {\n                    \"@type\": \"ImageObject\",\n                    \"url\": \"https://supertokens.com/static/assets/dark-home/logo.png\"\n                }\n            }\n        }</script>"
     }
 ]
\ No newline at end of file
diff --git a/static/blog-seo/sitemapconfig.json b/static/blog-seo/sitemapconfig.json
index 6f99447c..15545904 100644
--- a/static/blog-seo/sitemapconfig.json
+++ b/static/blog-seo/sitemapconfig.json
@@ -315,9 +315,7 @@
         "location": "https://supertokens.com/blog/ping-identity"
     },
     {
-
         "location": "https://supertokens.com/blog/auth-saas"
-
     },
     {
         "location": "https://supertokens.com/blog/top-auth0-alternatives-in-2025"
@@ -432,5 +430,11 @@
     },
     {
         "location": "https://supertokens.com/blog/launch-week-1-recap"
+<<<<<<< HEAD
+    },
+    {
+        "location": "https://supertokens.com/blog/cors-errors"
+=======
+>>>>>>> master
     }
 ]
\ No newline at end of file
diff --git a/static/card_covers/cors_errors.png b/static/card_covers/cors_errors.png
new file mode 100644
index 00000000..89417ca8
Binary files /dev/null and b/static/card_covers/cors_errors.png differ
diff --git a/static/covers/cors_errors.png b/static/covers/cors_errors.png
new file mode 100644
index 00000000..89417ca8
Binary files /dev/null and b/static/covers/cors_errors.png differ