Screenshot of Test262 Report displaying the language syntax folder

Test262 Report


Daily runs of Test262 against nightly builds of all major JavaScript Engines.

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A developer-centric report on the state of JavaScript engine interoperability and conformance.


Test262 is the official JavaScript language conformance test suite, containing comprehensive test material for each feature in the JavaScript language. New language features require these tests as entrance criteria for inclusion in the ECMAScript® Language Specification, and implementers rely on these shared tests in order to implement new features correctly and confirm completeness prior to release. This makes Test262 results the ground truth for the state of a JavaScript feature. Existing JavaScript compatibility sites for developers have historically relied on anecdotal knowledge of JavaScript engine support based on manual testing or automated but shallow "existential" tests.


We built a CI infrastructure for running the latest version of the Test262 material in each of the nightly versions (when available) of JavaScript engines in both default and strict modes, as well as in module code when ES Modules are present.

We used open source tools so anyone can reproduce these results; Test262-harness for running eshost as our global namespace map across engines, and jsvu to install the latest engine binaries.


JavaScript developers now have a tool to get up-to-date information on the state of new and existing language features across implementations. Specification authors at TC39 (the Technical Committee that writes EcmaScript) can now quickly check the Stage 3 progress of a feature prior to advancing it to Stage 4 (“Finished”) and including it in the specification. And finally, engine implementers can now quickly assess other engine implementation statuses to prioritize their work.

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