It can be difficult to keep  up with the latest browsers, so what is new in Firefox 18 and Chrome 24 both of which have just become available on the release channels.

The big improvement in Firefox 18 is IonMonkey, the replacement for the SpiderMonkey JavaScript engine.

IonMonkey provides a brand new architecture that allows for optimizations to be introduced into JavaScript JIT compilation. It differs from previous compilers by including an intermediate representation (IR) and has three steps:

1. Translate JavaScript to an intermediate representation (IR).
2. Run various algorithms to optimize the IR.
3. Translate the final IR to machine code.

The optimizations include:

• Loop-Invariant Code Motion (LICM), or moving instructions outside of loops when possible.
• Sparse Global Value Numbering (GVN), a powerful form of redundant code elimination.
• Linear Scan Register Allocation (LSRA), the register allocation scheme used in the HotSpot JVM (and until recently, LLVM).
• Dead Code Elimination (DCE), removing unused instructions.
• Range Analysis; eliminating bounds checks
  
  

The speed improvements vary greatly depending on the nature of the program being optimized, but Mozilla has been claiming anything from 5% to 20% improvements. The suggestion is that you should check out BananaBread, a 3D Web game created by the Mozilla Developer Network and powered exclusively by HTML5, WebGL and JavaScript.

The other two important features are:

• Support for Retina Display on OS X 10.7 and up.
• Preliminary support for WebRTC.

Just after Firefox 18 was released, Chrome 24 was pushed out to the stable channel. The main claim to fame for this release is also speed. In this case Google is claiming an overall 25% speed increase and not just in JavaScript. Chrome has been tuned so that it works faster and loads faster. The other main enhancement is support of MathML - an XML like layout language for mathematical expressions. In addition the new version is claimed to fix a great many bugs and security problems.

It does, however, appear to be experiencing teething troubles so if you have the option don't be amongst the very first to upgrade.

Once the dust has settled, Firefox 18 and Chrome 24 are both welcome new versions and overall the fast and automatic upgrade policies adopted by Google and Mozilla seem to be delivering more benefits than problems but the days of the "big new browser" seem to be over. It all raises the question of where are the browsers going in the future. For most of us the big issues are adding new features to make web apps not only possible but attractive. At the moment all three major browsers are being slow to catch up with reality - with IE being the slowest.