An origin is defined as a combination of URI scheme, host name, and port number. Same Origin Policy prevents a web site’s scripts from accessing and interacting with scripts used on other sites. In other words, this policy prevents a malicious script on one page from obtaining access to sensitive data on another web page through that page’s Document Object Model.

Cross-Origin Resource Sharing

The second technique for relaxing the same-origin policy is standardized under the name Cross-Origin Resource Sharing. This standard extends HTTP with a new Origin request header and a new Access-Control-Allow-Origin response header. It allows servers to use a header to explicitly list origins that may request a file or to use a wildcard and allow a file to be requested by any site.

Read more: Why is the same origin policy important?