This article walks through common CORS errors encountered when a frontend on http://localhost:8080 calls a backend on http://localhost:59200, explains the role of the four CORS response headers, the preflight OPTIONS request, and provides step‑by‑step Nginx configurations to resolve each case.
This article explains the browser's same‑origin policy, why it exists to prevent attacks such as XSS and CSRF, how origins are defined by protocol, host and port, and how CORS, simple requests, and preflight requests enable controlled cross‑origin communication.
POST requests can be sent twice in cross‑origin scenarios because browsers issue a CORS preflight OPTIONS request first, and only after the server approves the request does the actual POST occur; understanding same‑origin policy, simple vs complex requests, and proper server header configuration prevents this duplication.
This article explains the fundamentals of the browser's same-origin policy, its security implications, how it restricts DOM, web data and network access, and provides a detailed overview of CORS, including simple requests, preflight checks, required headers, and best practices for safe cross-origin communication.
This article walks through why browsers block cross‑origin requests, explains the four CORS response headers, demonstrates how to test preflight requests, and provides multiple Nginx configuration examples—including handling OPTIONS, custom headers, and method restrictions—to reliably resolve CORS issues.
This article explains the browser's same‑origin policy, its role in preventing XSS, CSRF and other attacks, details the protocol, host and port rules, illustrates with examples, and then describes CORS, simple and preflight requests, credential handling, and provides a complete request flow diagram.
This article explains the same‑origin policy, its role in protecting browsers from XSS, CSRF and other attacks, illustrates how origins are defined with protocol, host and port, and details how CORS, simple requests and preflight requests enable controlled cross‑origin communication.
This article explains the browser's Same‑Origin Policy, its role in preventing XSS, CSRF and other attacks, and details how Cross‑Origin Resource Sharing (CORS) works, including simple requests, preflight requests, credential handling, and provides a complete request flow diagram.
This article explains how to diagnose and fix common CORS problems when a front‑end site on port 8080 accesses a back‑end service on port 59200 by configuring Nginx as a proxy, detailing the required response headers, handling preflight requests, and providing complete example configurations.
This guide walks through diagnosing common CORS failures, explains the four essential response headers, and provides step‑by‑step Nginx configurations—including handling preflight OPTIONS requests, custom headers, and method restrictions—to reliably resolve cross‑origin issues during development.
This guide walks through preparing a local frontend and backend, explains the four essential CORS response headers and preflight requests, then presents five common CORS error cases with step‑by‑step Nginx configuration fixes and a complete working example.
This article shares a hands‑on journey of solving cross‑origin issues in a multi‑domain education product, covering CORS fundamentals, simple and preflight requests, Nginx and SpringBoot configurations, response‑code choices, and Chrome’s insecure private‑network restrictions, with practical solutions and lessons learned.
This article explains the CORS standard, how browsers enforce same‑origin policy, the definitions of simple and preflight requests, required HTTP headers, credential handling, and typical configuration mistakes that cause CORS errors, illustrated with code examples and tables.
This article walks through the root causes of CORS errors, explains the four essential response headers, demonstrates how to test with Postman, and provides a series of Nginx configuration examples that progressively fix preflight, header, method, and credential problems for a local development environment.
This article explains the mechanics of CORS, detailing how browsers decide whether a cross‑origin request is executed directly, blocked, or preceded by a preflight OPTIONS request, and distinguishes between simple and complex requests based on method, headers, and other criteria.
This article explains the CORS mechanism, detailing how browsers automatically add Origin headers, the difference between simple and non‑simple requests, the preflight exchange, required HTTP headers, and how servers respond to enable or reject cross‑origin communication.
The article explains why CORS distinguishes between simple requests—limited to GET, HEAD, POST with specific headers and content types—and preflighted requests, describing the server‑side rationale, the mechanics of preflight, and why avoiding preflight for simple requests simplifies cross‑origin interactions.
This article explains how browsers handle CORS by distinguishing simple and non‑simple requests, the conditions that trigger a preflight OPTIONS request, the required Access‑Control response headers, and how server‑side implementations—such as Java interceptors—manage these interactions.
