Individual skill
cross-origin-isolation
Use when reviewing security-sensitive web apps, SharedArrayBuffer usage, worker-heavy apps, editors, or measurement features that require cross-origin isolation. Check both headers and real browser behavior.
skills/cross-origin-isolation/SKILL.md
Source commit e8d14d049010e2ce25afcd5e8609dfcbbe63e47e
What was checked
- Matches the observed repository HEAD
- Yes
- Scanner rules are current
- Yes
- Repository scan complete
- No
- Skill scan complete
- Yes
- Observed behavior
- Instructions only
- Last checked
- Nov 9, 2026
These are observations at the recorded commit, not a guarantee of safety. Review the source before running it.
Install this skill
Choose an agent in your Stack or copy a command below. Commands fetch the pinned commit and copy only this skill directory. Existing destinations are refused. Copying a command does not install anything.
An install command is unavailable: current rules, complete repository and skill scans, an eligible behavior level and a permitted license are required.
Repository context
- Repository stars (not skill ratings)
- 74,700
- Repository last updated
- Oct 31, 2026
- License
- MIT
Observed agent integration: No specific integration evidence. Standard SKILL.md installation does not imply verified compatibility.
- frontend Repository topic
- front-end-development Repository topic
- front-end-developer-tool Repository topic
- guidelines Repository topic
- checklist Repository topic
- reference Repository topic
- web-development Repository topic
- html Repository topic
- css Repository topic
- javascript Repository topic
- security Derived category
Files and excerpt
File metadata and permitted, redacted excerpts come from the recorded scan. Source links are pinned to that commit.
Browse files
SKILL.mdcore · 2,257 bytesreferences/rule.mddoc · 4,029 bytes
Read excerpt
# Use COOP, COEP, and CORP for cross-origin isolation when needed
Cross-origin isolation reduces opener-based attacks and XS-Leak risk, and it is required for powerful browser features such as SharedArrayBuffer in modern browsers. It also breaks integrations if deployed carelessly, so it needs a deliberate rollout rather than a copy-pasted header block.
## Quick Reference
- Use `Cross-Origin-Opener-Policy` and `Cross-Origin-Embedder-Policy` together when you need cross-origin isolation
- Audit every cross-origin script, iframe, image, worker, and font before enforcing COEP
- Serve embeddable resources with CORS or `Cross-Origin-Resource-Policy` as appropriate
- Verify `self.crossOriginIsolated === true` before depending on isolated-only features
## Check
Review security headers and embedded resources for cross-origin isolation. Check whether the app needs COOP/COEP, whether resources are compatible with COEP, and whether the runtime actually becomes crossOriginIsolated.