| name | subresource-integrity |
| description | Use when reviewing templates, rendered HTML, or shared components related to Add Subresource Integrity to external scripts. Validate the final browser-facing markup, not just the source framework abstraction. |
| metadata | {"category":"html","priority":"high","difficulty":"intermediate","estimatedTime":"15","source":"frontendchecklist.io","url":"https://frontendchecklist.io/en/rules/html/subresource-integrity"} |
Add Subresource Integrity to external scripts
When you load JavaScript from a CDN, you're trusting that CDN completely — if it's compromised, attackers can serve malicious JavaScript to all your users. SRI adds a cryptographic hash to the tag; the browser refuses to execute the script if the hash doesn't match the downloaded content, protecting users even if the CDN is compromised or the URL is hijacked.
Quick Reference
- Add integrity="sha384-..." to
- Always pair integrity with crossorigin="anonymous"
- Generate hashes with openssl or online tools — CDN providers usually supply them
- SRI blocks execution if the file hash doesn't match, preventing CDN compromise attacks
Check
Find all external
Fix
Add appropriate integrity and crossorigin attributes to external CDN resources. Generate the SHA-384 hashes for each resource.
Explain
Explain Subresource Integrity, how it protects against CDN compromise, how to generate SRI hashes, and its limitations.
Code Review
Review templates, server-rendered HTML, and shared components that output markup related to Add Subresource Integrity to external scripts. Flag exact elements, attributes, and routes where the rendered HTML violates the rule.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/html/subresource-integrity
