As Netscape and Microsoft added features, they also refined and optimized the code for size and speed. This made performance acceptable, but vestiges of Mosaic's design meant neither could offer the speed of a browser coded from scratch. Demanding market timing and fierce competition meant that neither of the Big Two could afford the time or resources necessary to re-code their browsers from scratch. The fact that Opera was a new product meant the developers could devote all of their resources to making their browser faster. They accomplished this by avoiding third-party libraries and focusing on optimizing their own code.
Opera loads fast, in a fraction of the time of other browsers, and quickly renders pages.
While highly-optimized code usually means longer lead times for implementing additional features, Opera hasn't seemed to suffer from this yet. As a testament to their industrious developers, they continue to crank out new versions like clockwork. Size matters Another of Opera's design goals was size. Like the Big Two's browsers, Opera includes integrated mail and news clients. However, these are the least mature modules in Opera and are probably best replaced by third-party alternatives.