How the JavaScript Test Works
Page Confirms JS Execution on Load
Feature Detection Checks Modern JS APIs
Run Optional Performance Benchmark
View Full Compatibility Report
What is a JavaScript Test?
A JavaScript Test confirms whether JavaScript is enabled and running in your browser, checks support for modern JavaScript language features and APIs, and can benchmark your browser's raw JavaScript execution performance. Since nearly all modern websites rely heavily on JavaScript for interactivity — from simple dropdown menus to complex web applications — confirming it's working correctly is often the first troubleshooting step when a website isn't behaving as expected.
This free online tool goes beyond a simple "yes/no" check by testing support for specific modern JavaScript features (like Promises, async/await, and ES6 syntax) and providing a quick performance benchmark, which can be useful for comparing execution speed across different browsers or devices.
Why JavaScript Matters for Modern Websites
JavaScript powers the interactive layer of nearly every modern website — form validation, dynamic content loading, animations, single-page applications, real-time updates, and much more. If JavaScript is disabled or blocked (whether by browser settings, a corporate policy, or a browser extension), many websites will fail to function correctly, sometimes showing blank pages, broken layouts, or missing functionality without any clear error message explaining why.
Common Reasons JavaScript Might Be Disabled
| Cause | How to Fix |
|---|---|
| JavaScript manually disabled in browser settings | Re-enable JavaScript in your browser's site/content settings |
| Aggressive ad-blocker or script-blocking extension | Whitelist the specific site or temporarily disable the extension |
| Corporate/school network content filtering | Contact your network administrator if on a managed network |
| Browser security settings set too restrictively | Adjust security/privacy settings to a less restrictive level |
| Outdated browser lacking modern JS support | Update to the latest version of your browser |
Modern JavaScript Features Explained
- Promises & Async/Await: Modern syntax for handling asynchronous operations like data fetching, replacing older callback-based patterns.
- Arrow Functions & Template Literals: ES6 syntax improvements that make JavaScript code more concise and readable.
- Fetch API: The modern standard for making network requests from JavaScript, replacing the older XMLHttpRequest approach.
- Web Workers: Allow JavaScript to run in background threads, keeping the main page responsive during heavy computations.
- Proxy & Reflect: Advanced object manipulation features used by many modern frameworks and libraries.
Understanding the Performance Benchmark
The performance benchmark runs a series of computational operations (like array manipulation and mathematical calculations) and measures how many operations your browser can complete per second. While this isn't a comprehensive professional benchmark, it gives you a useful relative comparison — for example, testing the same page across different browsers or devices to see which executes JavaScript faster, or checking whether an older device shows meaningfully reduced performance compared to a newer one.
Frequently Asked Questions
If I can see this page's content, does that mean JavaScript works?
The dynamic status message and feature checklist on this page only appear if JavaScript successfully executes, so seeing them confirms JavaScript is enabled and running correctly.
A feature shows as "not supported" - is my browser outdated?
Possibly. Most modern browsers support all the commonly tested features listed here, so a failure often indicates either an outdated browser version or the feature being explicitly disabled in settings.
Why would I need to disable JavaScript?
Some users disable JavaScript for privacy, security, or performance reasons on low-powered devices, though this significantly limits functionality on most modern websites.
How is the performance benchmark score calculated?
It measures how many computational operations your browser completes within a fixed time window, giving a relative performance figure useful for comparison rather than an absolute industry-standard score.