300ms Faster: Reducing Wikipedia’s Total Blocking Time

Wikipedia’s mobile site experienced performance issues due to a piece of JavaScript that could take over 600ms to execute during page load. This resulted in rage clicking, increased bounce rates, and lower search engine ranking. Google considers any task that takes more than 50ms a “long task” that can affect the page’s responsiveness to user input and developed a metric called “Total Blocking Time” (TBT). To reduce TBT, the JavaScript code was optimized by removing unnecessary JavaScript and using event delegation. These two steps resulted in a reduction of TBT by nearly 300ms on devices like the Moto G (5) phone visiting long articles.


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