Quick answer
Safe JavaScript Playground: Browser Sandbox and Limits
Myztic Playground runs client-side HTML, CSS, and JavaScript in a capability-restricted browser preview, but it should not be treated as a secure environment for unknown or untrusted code.
At a glance
Why iframe sandboxing helps
Preview code cannot use the playground origin, DOM, cookies, or local storage, and its network requests are blocked.
What users should not paste
Do not paste API keys, passwords, personal data, or unknown scripts from untrusted sources.
Frontend versus backend
Myztic renders client-side browser code; it does not run server languages, databases, packages, or private environment variables.
Frequently asked questions
Is all JavaScript safe to run here?
No. The sandbox limits capabilities but cannot inspect or prove arbitrary code safe.
Can preview code reach the playground page?
No. The iframe does not receive same-origin access.
Can heavy code freeze my tab?
Yes. Resource-heavy scripts can still slow or freeze the current browser tab.
Can I run backend code?
No. Myztic Playground is limited to client-side browser code.