GuardJS
A tiny, dependency-free script that detects weak or risky client environments and warns users only when it actually matters. No tracking. No noise. No backend.
What this does
Capability Guard checks real browser and device signals such as memory limits, storage availability, disabled APIs, or extreme constraints and lets you gracefully inform users when their setup may break core functionality.
It does nothing on healthy devices. No banners. No alerts. No visual clutter. The script stays invisible unless a real degradation risk is detected.
<script src="https://guardjs.netlify.app/capability-guard.min.js"></script>
Drop it once. Configure later if needed. Works offline.
Free examples
If an example doesn’t trigger for you, it means Capability Guard has already
handled this site on your device.
Notice-based examples are shown only once to avoid repeated interruptions.
Redirect mode, however, is evaluated on every visit since it represents a routing decision.
To re-test notice examples, clear the site data or open them in an incognito/private window.