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Comment by rotrux | Hacker News Reader

Forgive my webdev nievete, but what exactly is a Browser Engine, and how is it different from a browser? Is this like selenium? What's the use-case? Why is parallelism important in this context?

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The browser engine gets HTML, parses it, and turns it into an array of pixels. Hopefully without crashing and without any security vulnerabilities. The rest of the browser is the UI built around this engine - it reads your URL bar, tells the engine to render the page, and handles things like navigation and bookmarks and saved passwords etc.

Browser engines also execute the JavaScript, though I'm pretty sure Servo just does the HTML/CSS rendering. Webpages these days are very heavy which is why parallelism is important (for both the layout engine as well as the JS engine).

Servo uses an existing JS interpreter (SpiderMonkey, the one used in Firefox) but does implement all of the Web APIs itself.

It's like the browser's kernel. You can build different browsers on top of the same engine without having to write everything from scratch. Chrome, Opera, Edge and Brave all share the same Blink/Webkit engine and there are a bunch of Firefox forks like Palemoon that share its Gecko engine.

Servo is a new engine written from scratch that's progressively replacing Gecko in Firefox: https://wiki.mozilla.org/Quantum

It's the (large) piece of a browser that is displaying the websites.

Parallelism is interesting to make them faster by using multiple processor cores, today probably most interesting for mobile devices.

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