Instantly audit your browser's JavaScript engine capabilities with our free JS Version Checker. Test ECMAScript standards from ES5 through ES2024 using live feature probes, detect V8/SpiderMonkey/JavaScriptCore engine identification, and verify modern API support — all 100% offline with zero telemetry.
ES feature checks fire instantly on page load — no input or click needed.
Review each ES standard's pass/fail status from ES5 strict mode up to ES2024 Object.groupBy.
View the detected JS engine, highest ES standard supported, and total features passed count.
Probes 11 ECMAScript milestones using runtime eval, prototype checks, and global typeof guards to confirm each feature accurately.
Identifies V8 (Chrome/Edge Blink), SpiderMonkey (Firefox Gecko), and JavaScriptCore/Nitro (Safari WebKit) from User-Agent strings.
All feature probes execute locally inside your browser — no network requests, no diagnostic data sent to BunchTool servers.
ECMAScript feature detection uses three techniques: (1) typeof check on global objects (e.g. typeof BigInt !== 'undefined'), (2) prototype presence checks (e.g. typeof Array.prototype.at === 'function'), and (3) wrapped eval() calls to parse new syntax that older engines would throw SyntaxError on (e.g. async/await, rest/spread properties).
JavaScript engine identification relies on User-Agent string parsing: "Chrome" or "Edg" tokens indicate Google's V8 engine; "Firefox" indicates Mozilla's SpiderMonkey; "Safari" without Chrome indicates Apple's JavaScriptCore (also known as Nitro).
The highest consecutive passing ES standard is reported as the estimated engine version. For example, a browser supporting ES2023's Array.prototype.findLast but not ES2024's Object.groupBy will report ES2023 (ES14).