Presto

Presto is a layout engine for the Opera web browser developed by Opera Software. After several public betas and technical previews, it was released on January 28, 2003 in Opera 7.0 for Windows; it is the browser's current layout engine. Presto is dynamic; the page or parts of it can be re-rendered in response to DOM and script events. Presto is available only as a part of Opera browser or related products. The source or binary (DLL) forms of the engine are not publicly available. Subsequent releases have seen a number of bugs fixed and optimizations to improve the speed of the ECMAScript ("JavaScript") engine.

JavaScript engines
The "Linear A" is a JavaScript engine used in older versions of Opera. Versions based on the "Core" fork of Presto, Opera 7.0 through 9.27, use the "Linear B" engine The "Futhark" engine is used in some versions on the "Core 2" fork of Presto, namely Opera 9.5 to Opera 10.10. When released it was the fastest engine around, but in 2008 a new generation of JavaScript engines from Google (V8), Mozilla (TraceMonkey) and Apple (SquirrelFish) took one more step, introducing native code generation. Though raw JavaScript performance is of very little meaning in everyday browsing, this opened up for potential heavy computations on the client side and futhark, though still fast and efficient, would not be able to keep up.

In early 2009, Opera presented the next step, Carakan (named after the Javanese script), which will be used in future versions of Opera. It features register-based bytecode, native code generation, automatic object classification and overall performance improvements. Early access in the Opera 10.50 pre-alpha showed that it's as fast as the fastest competitors, being the winner in 2 out of the 3 most used benchmarks.