Same Origin Policy
Same Origin Policy (SOP) is a critical web security mechanism implemented by web browsers to restrict how documents or scripts loaded from one origin can interact with resources from another origin. It prevents malicious websites from accessing sensitive data from other sites, such as cookies, local storage, or DOM elements, thereby protecting user privacy and security. The policy defines an 'origin' as a combination of protocol, host, and port, and only allows interactions between resources that share the same origin.
Developers should learn SOP to build secure web applications that prevent cross-site scripting (XSS) and cross-site request forgery (CSRF) attacks, which are common web vulnerabilities. It is essential when implementing features like iframes, AJAX requests, or third-party integrations, as understanding SOP helps in properly configuring Cross-Origin Resource Sharing (CORS) to allow controlled cross-origin access. For example, when fetching data from a different domain via an API, developers must set appropriate CORS headers to comply with SOP while enabling necessary functionality.