Launched as an experimental project, the Servo browser engine is nearing its first release, scheduled for this June, as Mozilla's engineers have revealed in an internal discussions group.

Servo started as an experimental project belonging to the Mozilla Research team, which set out to build a sleeker Web layout engine as an alternative to Firefox's default engine called Gecko.

The difference between Servo and Gecko is that the former was coded entirely in Rust, a programming language that Mozilla developed for its applications, focused on performance and stability, something that Firefox was lacking at that particular point in time. (See the comment from Springroll below the article, for more insight in how Servo differentiates from Gecko)

Everything in Servo is a component, each with its own task and separated from the rest as much as possible, with the aim of reducing friction between misbehaving components and allowing for easy debugging and fixing of any future problems that may arise.

The project started out as a moonshot, but after Samsung lent a helping hand for Android builds, Mozilla got more courage to develop it further, more than just an alternative engine for Firefox.

Servo will feature an HTML-CSS-JS-based UI

Currently, Mozilla plans to release Servo as a standalone browser in June this year, with builds for Android, Firefox OS, Mac, Linux, and Windows.

"To be clear, this will be a very early release (nightly builds) of Servo with a HTML UI (browser.html)," Mozilla's Paul Rouget explained. "You won't be able to replace your current browser with Servo just yet :) … there's still a long way to go. The goal is to make it easier for people to test Servo and file bugs."

This also ties in with some leads we reported on in July 2015. Back then, we stumbled upon a Mozilla project called browser.html, which the foundation described as "an idea" into an alternative UI for Firefox.

Since at that time Servo was still an experimental, half-finished, and non-functional project, we bought into the idea that browser.html would be a possible replacement for Firefox's default UI, one made entirely out of HTML, CSS, and JavaScript.

With today's news, it now appears that Mozilla never intended to use browser.html for Firefox, or at least not yet. Revisiting browser.html's GitHub project today, we see that it's described as "a research project aimed at building an experimental Servo browser in HTML."

If you're curious how Servo might look, this is the latest preview of browser.html in action, while below is a Servo preview from September 2014. Additionally there's this tweet from last August. As you can see from all previews, there's a certain "spartan" feel to Servo.

Mozilla never said it would be replacing Gecko with Servo, but we'd imagine that if Servo fairs better than previously expected, some of its components might slowly make their way inside future versions of Firefox, and why not, eventually replace Gecko.

Servo is to Firefox what Edge is to Internet Explorer

The way Mozilla is sneakily working on another browser reminds us of how Microsoft started work on Edge. If you remember, Microsoft continued to develop the bulky, outdated, and sometimes very insecure Internet Explorer browser, but also worked on a small browser, which it internally called Spartan, due to a lack of many useful features.

As the project grew and grew, it became apparent to everyone that Microsoft was working on an IE alternative, entirely different and using a completely new architecture from what IE was using.

Spartan was eventually renamed to Edge, and when Windows 10 launched, Edge, not IE, was the operating system's default browser.

As things are looking right now, Mozilla is indeed preparing to launch a lightweight browser in the same sneaky way Microsoft launched Edge, so if you want to start the rumors of "Servo will replace Firefox," you may have a valid point to back up your arguments.

Will Servo replace Firefox, or will Firefox absorb all of Servo's good parts?

But let's keep it clear. Until today, Mozilla has never ever said it's planning to replace Firefox, so we may all look like fools in a couple of months, when Servo miserably fails, and Mozilla continues its work on Firefox, in which it put quite some effort in giving a facelift.

Upcoming Firefox versions include MAJOR (sorry for the caps, but it was needed) changes, like the new WebExtensions API (facelift of the browser's add-ons capabilities), mandatory add-ons signing, and e10s (multi-process support).

A more likely scenario would be our first theory, the one that said that, if stable enough, Servo will be slowly merged in Firefox and replace the bulky Gecko C++-based engine with Mozilla's Servo Rust-based core. This would also validate the foundation's efforts into developing Rust, which has failed to gather any type of following outside the Foundation.

UPDATE: The article was updated to correct a factual error that Rust was used in Firefox OS.