CORS Header Generator
Generate the correct Access-Control headers for your API with a visual builder.
Access-Control-Allow-Origin: * Access-Control-Allow-Methods: GET, POST, PUT, DELETE Access-Control-Allow-Headers: Content-Type, Authorization Access-Control-Max-Age: 86400
About this tool
CORS (Cross-Origin Resource Sharing) is a web security mechanism that allows servers to explicitly grant permission for browsers to access resources from different domains. When your frontend runs on one domain and needs to fetch data from an API on another domain, the browser blocks the request by default for security reasons. CORS headers tell the browser which cross-origin requests are allowed, making it essential for building modern web applications that integrate multiple services or connect to third-party APIs.
To use this tool, select the HTTP method your API will receive (GET, POST, PUT, DELETE, etc.) and specify which domains are allowed to access your resources. You can also configure whether credentials like cookies should be sent with cross-origin requests, which HTTP headers are permitted, and how long browsers can cache the CORS policy. The tool generates the exact header code you need to add to your server configuration or API responses, ready to copy and paste into your backend.
CORS headers are critical for APIs serving web applications, SPAs (Single Page Applications), mobile apps, or any frontend connecting to a different domain. Understanding CORS prevents common errors like "blocked by CORS policy" and ensures your API is accessible to legitimate clients while maintaining security boundaries. Most modern frameworks (Express, Django, FastAPI, ASP.NET) include CORS middleware, but this tool helps you configure the correct headers even if you're implementing CORS manually or need to verify your existing configuration.
Frequently Asked Questions
Code Implementation
# Flask β cors with flask-cors
from flask import Flask
from flask_cors import CORS
app = Flask(__name__)
# Allow specific origin
CORS(app, resources={r"/api/*": {
"origins": "https://example.com",
"methods": ["GET", "POST", "PUT", "DELETE"],
"allow_headers": ["Content-Type", "Authorization"],
"supports_credentials": True,
"max_age": 86400
}})
# Manual CORS headers in a response
from flask import make_response
@app.after_request
def add_cors_headers(response):
response.headers["Access-Control-Allow-Origin"] = "https://example.com"
response.headers["Access-Control-Allow-Methods"] = "GET, POST, OPTIONS"
response.headers["Access-Control-Allow-Headers"] = "Content-Type, Authorization"
return responseComments & Feedback
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