What just happened? A recent preview version of Firefox was seemingly able to beat Chrome in the SunSpider JavaScript benchmark, an old speed test from Apple's WebKit team. The team celebrated and posted a screenshot of the feat even though other more recent benchmarks continue to rank Google's browser as the fastest overall.

Mozilla Firefox is the only modern alternative to Google Chrome and third-party browsers based on the Chromium engine, but it's still lacking something in the performance department. Chrome was created to speed up web development, and it arguably provides the fastest experience overall. But Mozilla's software has recently made strides – in one specific benchmark, at least.

A recent release of Firefox Nightly, which came out last week, has managed to outperform Chrome in the SunSpider JavaScript benchmark, as announced by Mozilla developers. According to the Firefox Performance Dashboard (FPD) website, Firefox began to outpace Chrome in the SunSpider benchmark at the end of June. This new performance metric appears to hold its validity up to the present day.

SunSpider is a benchmark originally developed by Apple to evaluate JavaScript performance in the WebKit (Safari) layout engine, as well as in other third-party browsers. The test is rooted in real-world JavaScript usage scenarios and includes specific assessments for encryption routines, text manipulation, and other aspects. The initial version of SunSpider was launched in 2007, with the last version (1.0) dating back to April 2013. However, the benchmark has since been replaced by the JetStream test suite.

JetStream serves as a modern and more rigorous benchmark for evaluating JavaScript performance. The FPD site confirms that Chrome remains the fastest browser in comparison to Firefox in this and other recent benchmarks. On the other hand, Speedometer, a benchmark designed to measure JavaScript throughput, indicated that Firefox had been making strides to catch up to Chrome, but has since reverted to being the slower browser.

Mozilla regularly tests Firefox's performance against Chrome throughout the day, with developers also striving to enhance their code in various aspects. The same version of Firefox Nightly that showcased the browser's improved speed in the SunSpider benchmark introduced numerous changes that are expected to become more apparent in the coming months.

Changes include a new version of the Firefox View management tool, enhancements in upload speed over HTTP/2, extended support for credit card auto-fill in additional regions, and more.

Firefox Nightly stands among the three "experimental" versions of the FOSS browser provided by Mozilla. In comparison to the Beta and Developer Edition channels, Nightly releases are more prone to disruptions, displaying bugs and inconsistencies while Mozilla continues to work on the "next generation."