Mobile Web performance challenges and strategies

DEC 15, 2011
Author Photo
By Ramki Krishnan, Technical Program Manager

Consumers are increasingly relying on their mobile devices to access the Web, thrusting mobile web performance into the limelight. Mobile users expect web pages to display on their mobile devices as fast as or faster than on their desktops.

As part of Google’s effort to Make The Web Faster, we invited Guy Podjarny, CTO of, to talk about some of the major performance concerns in the mobile web and ways to alleviate these issues. Guy’s talk focused on Front-End Optimization and highlighted 3 areas: mobile network, software, and hardware. Each of these impacts performance in myriad ways. The full video is available here, and runs just under an hour. If you don’t have time to watch this enlightening talk, this post discusses some key takeaways.

Mobile networks have high latency, and reducing the number of requests and the size of downloads are well-known optimization strategies. Guy also mentions using on-demand image displays such as loading above-the-fold images by default and other images only as they scroll into view. To handle network reliability, he recommends non-blocking requests eliminating single points of failure, with a selective aggregation of files needed for content display. Periodic pinging of the cell tower by the client can also reduce latency associated with dropped connections, but judicious timeouts and battery drain on the mobile device need to be factored in.

Modern mobile browsers are built mobile-friendly, and they can be helped further by exploiting localStorage to store CSS and JavaScript files. Pipelining multiple requests on a connection is an option, but developers need to work around head-of-line blocking by using techniques such as splitting dynamic and static resource requests on different domains.

Mobile hardware CPUs are weaker than their desktop counterparts. Guy points out the need to minimize JavaScript when designing mobile-friendly web pages and avoid reflows or defer JavaScript until after page loads. Clever image rendering techniques such as automatically resizing images to devices and loading full resolution only on zoom can also help.

Guy’s presentation makes clear that mobile web optimizations need to mitigate latencies introduced by mobile networks, software, and hardware. Rapidly changing OSes and browsers add to the challenges facing publishers. New and evolved tools and technologies will help ensure an optimal web browsing experience for mobile users.

Ramki Krishnan works at Google on the "Make The Web Faster" team. When not at work, he dreams of being a tennis pro, a humorist, and a rock drummer all rolled into one.

Posted by Scott Knaster, Editor