Blog Developer Blog Render Pages Faster for Optimized Browsing, Part 5 of 5 Web browsers handle every single task on the main thread. Script execution, user interactions, and the rendering process described below all occupy the main thread. This means that browsers can only do one thing at a time. If too much time is spent on script execution and rendering, then user interactions can only occur after the main thread frees up — and if this takes too long, users may become impatient. \r\n The deciding factor becomes when the main thread is first freed up. This could be either before or after the point when all HTML assets become available. For instance, when an image takes a long time to load, the main thread idles for a while. The browser can then decide to start the rendering process. It may need to re-render the page once the image arrives at an indeterminate time, but showing something is always better than showing nothing.…