What is CORS?
Cross-Origin Resource Sharing, a browser security policy governing cross-domain HTTP requests.
Definition
CORS (Cross-Origin Resource Sharing) is a browser security mechanism that controls which web domains can make HTTP requests to your server. When JavaScript on domain-a.com tries to fetch data from domain-b.com, the browser sends a CORS preflight request (OPTIONS) to domain-b.com. If domain-b.com responds with headers allowing domain-a.com, the actual request proceeds. CORS only applies to browser-based requests — server-to-server requests (like cron jobs) are not affected.
Simple Analogy
Like a bouncer at a club checking a guest list — your browser asks the server "is this website allowed to talk to you?" before sending the actual request. Server-to-server calls are VIPs that bypass the bouncer entirely.
Why It Matters
While CORS does not directly affect server-to-server cron job execution, it is critical when building dashboards or admin panels that call cron job APIs from the browser. If your CronJobPro integration includes a web interface that fetches job status from your API, CORS must be configured correctly on your API server.
How to Verify
Open browser developer tools and check the Console and Network tabs for CORS errors. Look for "Access-Control-Allow-Origin" headers in your API responses. Test preflight requests with: "curl -X OPTIONS -H 'Origin: https://your-frontend.com' https://your-api.com/endpoint" and verify the response includes appropriate CORS headers.
Common Mistakes
Setting "Access-Control-Allow-Origin: *" in production, which allows any website to call your API. Forgetting to handle OPTIONS preflight requests, causing all cross-origin requests to fail. Confusing CORS with server-side security — CORS is a browser-only mechanism and does not protect against server-to-server attacks.
Best Practices
Configure CORS to allow only specific trusted origins, not wildcards. Handle OPTIONS preflight requests explicitly in your server. Set appropriate Access-Control-Allow-Methods and Access-Control-Allow-Headers. Remember that CORS does not affect CronJobPro requests to your endpoint — those are server-to-server calls.
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Try it free →Frequently Asked Questions
What is CORS?
CORS (Cross-Origin Resource Sharing) is a browser security mechanism that controls which web domains can make HTTP requests to your server. When JavaScript on domain-a.com tries to fetch data from domain-b.com, the browser sends a CORS preflight request (OPTIONS) to domain-b.com. If domain-b.com responds with headers allowing domain-a.com, the actual request proceeds. CORS only applies to browser-based requests — server-to-server requests (like cron jobs) are not affected.
Why does CORS matter for cron jobs?
While CORS does not directly affect server-to-server cron job execution, it is critical when building dashboards or admin panels that call cron job APIs from the browser. If your CronJobPro integration includes a web interface that fetches job status from your API, CORS must be configured correctly on your API server.
What are best practices for CORS?
Configure CORS to allow only specific trusted origins, not wildcards. Handle OPTIONS preflight requests explicitly in your server. Set appropriate Access-Control-Allow-Methods and Access-Control-Allow-Headers. Remember that CORS does not affect CronJobPro requests to your endpoint — those are server-to-server calls.
Related Terms
CORS Policy
Server-side rules that control which web origins can make cross-domain HTTP requests.
HTTP Method
The verb (GET, POST, PUT, DELETE, etc.) that defines the type of action an HTTP request performs.
Request Header
Key-value metadata sent with an HTTP request to provide context like authentication and content type.
Endpoint
A specific URL where an API or service receives and processes HTTP requests.
Content-Type
An HTTP header that specifies the format of the request or response body (e.g., JSON, XML, form data).