Origin API
cursor/plugins
Routes questions about the Cursor Origin API to the right section of the Origin docs and names the few rules to check first.
A skill your agent uses when reviewing security-sensitive web apps, SharedArrayBuffer usage, worker-heavy apps, editors, or measurement features that require cross-origin isolation.
MITAuto-check passed
Install Cross Origin Isolation
$ npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install thedaviddias/Front-End-Checklist cross-origin-isolation --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/cross-origin-isolation .claude/skills/cross-origin-isolation && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "cross-origin-isolation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/cross-origin-isolation into .claude/skills/cross-origin-isolation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cross-origin-isolation", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/cross-origin-isolationType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install thedaviddias/Front-End-Checklist cross-origin-isolation --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/cross-origin-isolation .agents/skills/cross-origin-isolation && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "cross-origin-isolation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/cross-origin-isolation into .agents/skills/cross-origin-isolation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cross-origin-isolation", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install thedaviddias/Front-End-Checklist cross-origin-isolation --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/cross-origin-isolation .cursor/skills/cross-origin-isolation && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "cross-origin-isolation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/cross-origin-isolation into .cursor/skills/cross-origin-isolation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cross-origin-isolation", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/thedaviddias/Front-End-Checklist.git --path skills/cross-origin-isolation--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install thedaviddias/Front-End-Checklist cross-origin-isolation --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/cross-origin-isolation .gemini/skills/cross-origin-isolation && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "cross-origin-isolation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/cross-origin-isolation into .gemini/skills/cross-origin-isolation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cross-origin-isolation", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install thedaviddias/Front-End-Checklist cross-origin-isolationInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/cross-origin-isolation .github/skills/cross-origin-isolation && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "cross-origin-isolation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/cross-origin-isolation into .github/skills/cross-origin-isolation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cross-origin-isolation", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install thedaviddias/Front-End-Checklist cross-origin-isolation --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/thedaviddias/Front-End-Checklist.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/cross-origin-isolation .opencode/skills/cross-origin-isolation && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "cross-origin-isolation" agent skill from https://github.com/thedaviddias/Front-End-Checklist/tree/main/skills/cross-origin-isolation into .opencode/skills/cross-origin-isolation/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cross-origin-isolation", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
cross-origin-isolation- GitHub stars
- 74k
- Token cost
- ~565 tokens
- SKILL.md length
- 223 words
- Files
- 2 (incl. references)
- Skills in repo
- 390
- Repo updated
- First seen
- Licence
- MIT
At a glance
A skill your agent uses when reviewing security-sensitive web apps, SharedArrayBuffer usage, worker-heavy apps, editors, or measurement features that require cross-origin isolation.
- Reviewing security-sensitive web apps
- SKILL.md covers Quick Reference, Check, Fix and Explain, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
- SharedArrayBuffer usage
What it does
Cross Origin Isolation is an agent skill from thedaviddias/Front-End-Checklist. 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.
Its SKILL.md is about 570 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/rule.md`).
The repository describes itself as: 🗂 The essential checklist for modern web development, for humans and AI agents. The licence is MIT.
When your agent uses it
- Reviewing security-sensitive web apps
- SharedArrayBuffer usage
- Worker-heavy apps
- Measurement features that require cross-origin isolation
Example prompts
- “/cross-origin-isolation”
What it can do on your machine
Read from SKILL.md and the folder at commit e8d14d0. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
frontendchecklist.io
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Cross Origin Isolation loads about 565 tokens when it runs, and up to ~1.6k if it reads all its reference files. Until then it costs about 58 tokens; SKILL.md has 223 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from thedaviddias/Front-End-Checklist at commit e8d14d0, republished under its MIT licence (© thedaviddias). 223 words, ~565 tokens.
Download SKILL.mdSave it as
.claude/skills/cross-origin-isolation/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- cross-origin-isolation
- description
- 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.
- metadata.category
- security
- metadata.priority
- medium
- metadata.difficulty
- advanced
- metadata.estimatedTime
- 30
- metadata.source
- frontendchecklist.io
- metadata.url
- https://frontendchecklist.io/rules/security/cross-origin-isolation
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-PolicyandCross-Origin-Embedder-Policytogether 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-Policyas appropriate - Verify
self.crossOriginIsolated === truebefore 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.
Fix
Add COOP and COEP only after auditing dependencies, ensure subresources use CORP or CORS as required, and verify the final document becomes crossOriginIsolated in the browser.
Explain
Explain how COOP, COEP, and CORP work together, what they protect against, and why third-party embeds often block a successful rollout.
Code Review
Review server headers, third-party integrations, popups, workers, and asset responses related to Use COOP, COEP, and CORP for cross-origin isolation when needed. Flag exact responses or integrations that would block isolation or break once isolation is enforced.
For full implementation details, code examples, and framework-specific guidance,
see references/rule.md.
Rule page: https://frontendchecklist.io/rules/security/cross-origin-isolation
© thedaviddias, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file (references) in skills/cross-origin-isolation of thedaviddias/Front-End-Checklist.
- SKILL.md
- references/rule.md
Open the folder on GitHubat commit e8d14d0
Compare with similar skills
Cross Origin Isolation next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Cross Origin Isolation this skillthedaviddias/Front-End-Checklist | 74k | — | ~565 | Automated safety check: Pass | MIT | |
| Origin APIcursor/plugins | 11k | — | ~694 | Automated safety check: Pass | MIT | |
| Sensitive Logging Auditopenai/openai-agents-python | 30k | — | ~1k | Automated safety check: Pass | MIT | |
| Isolating Product Facade ContractsPostHog/posthog | 40k | — | ~9.6k | Automated safety check: Pass | Custom licence | |
| Implementing Browser Isolation For Zero Trustmukul975/Anthropic-Cybersecurity-Skills | 34k | — | ~3.5k | Automated safety check: Pass | Apache-2.0 | |
| Sensitivity Analystbrycewang-stanford/Auto-Empirical-Research-Skills | 4.6k | — | ~4.7k | Automated safety check: Pass | Custom licence |
Similar skills
- Official
- Official
Sensitive Logging Audit
openai/openai-agents-python
Audit or fix sensitive-data exposure in Python SDK diagnostics, exceptions, logging, and telemetry.
- Official
Isolating Product Facade Contracts
PostHog/posthog
Plan and execute product isolation migrations to a facade plus contract layer in PostHog, following the Visual review architecture.
Implementing Browser Isolation For Zero Trust
mukul975/Anthropic-Cybersecurity-Skills
Deploys remote browser isolation (RBI) as a core component of a Zero Trust architecture.
Sensitivity Analyst
brycewang-stanford/Auto-Empirical-Research-Skills
Sensitivity analysis frameworks and assumption-testing methods
Isolated Space Boundary
openchamber/openchamber
A skill your agent uses when changing isolated-space trust boundaries: container hardening, networks and gatekeeper policy, exec and lifecycle, grants and credentials, code transfer and apply…
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Questions about Cross Origin Isolation
What does Cross Origin Isolation do?
A skill your agent uses when reviewing security-sensitive web apps, SharedArrayBuffer usage, worker-heavy apps, editors, or measurement features that require cross-origin isolation. Cross Origin Isolation is an agent skill from thedaviddias/Front-End-Checklist. Use when reviewing security-sensitive web apps, SharedArrayBuffer usage, worker-heavy apps, editors, or measurement features that require cross-origin isolation.
When should I use Cross Origin Isolation?
Cross Origin Isolation fits situations like: reviewing security-sensitive web apps; sharedArrayBuffer usage; worker-heavy apps; measurement features that require cross-origin isolation.
How do I install Cross Origin Isolation in Claude Code?
Run `npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a claude-code`. Or copy the skill folder (skills/cross-origin-isolation in thedaviddias/Front-End-Checklist) into .claude/skills/cross-origin-isolation in your project. Claude Code loads it when a task matches its description.
How do I install Cross Origin Isolation in Codex?
Run `npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a codex`. Or copy the skill folder (skills/cross-origin-isolation in thedaviddias/Front-End-Checklist) into .agents/skills/cross-origin-isolation in your project. Codex loads it when a task matches its description.
Can I use Cross Origin Isolation in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add thedaviddias/Front-End-Checklist --skill cross-origin-isolation -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/cross-origin-isolation, .gemini/skills/cross-origin-isolation, .github/skills/cross-origin-isolation and .opencode/skills/cross-origin-isolation in your project.
What does Cross Origin Isolation need to run?
SKILL.md names no scripts, command-line tools or credentials: Cross Origin Isolation is instructions for the agent only.
Does Cross Origin Isolation access the network?
SKILL.md names 1 domain. As links in the text: frontendchecklist.io. This is read from the text; nothing was executed.
Is Cross Origin Isolation safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Cross Origin Isolation use?
Cross Origin Isolation is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Cross Origin Isolation use?
About 565 tokens (SKILL.md is roughly 2.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1k tokens, read only when the agent opens those files.
What are the alternatives to Cross Origin Isolation?
Skills that share tags, products or a category with Cross Origin Isolation: Origin API (cursor/plugins, 11k stars), Sensitive Logging Audit (openai/openai-agents-python, 30k stars), Isolating Product Facade Contracts (PostHog/posthog, 40k stars) and Implementing Browser Isolation For Zero Trust (mukul975/Anthropic-Cybersecurity-Skills, 34k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Cross Origin Isolation?
thedaviddias (a GitHub user) maintains it in thedaviddias/Front-End-Checklist, which has 74,421 GitHub stars. The repository holds 390 skills in this directory. The repository was last updated on October 6, 2026.
Source: thedaviddias/Front-End-Checklist on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.