Subresource Integrity (SRI) is a web development security mechanism that guarantees the authenticity and integrity of external resources like scripts and stylesheets. By including a cryptographic hash in the resource reference, browsers can verify that the resources haven't been tampered with before loading and executing them.

Subresource Integrity is present with warnings When not all resources on a website have Subresource Integrity (SRI) implemented correctly, and some external resources lack the necessary integrity hashes, the website's security is potentially compromised. This situation creates vulnerabilities, especially for resources loaded from third-party servers, where the site owner has less control. Consequently, the website may be exposed to security risks like malicious script execution, impacting both the site's integrity and the safety of its users.