Friday, January 5th, 2007

Browser Cache Usage: Only 40-60%?

Category: Yahoo!

Tenni Theurer has posted a second part of performance research on Browser Cache Usage – Exposed!.

The article measures the performance of with a full cache compared to an empty one (2.4s vs. 0.9s) and then shows a surprisingly low number of people heading over cached up:

40-60% of Yahoo!’s users have an empty cache experience and ~20% of all page views are done with an empty cache. To my knowledge, there’s no other research that shows this kind of information. And I don’t know about you, but these results came to us as a big surprise. It says that even if your assets are optimized for maximum caching, there are a significant number of users that will always have an empty cache. This goes back to the earlier point that reducing the number of HTTP requests has the biggest impact on reducing response time. The percentage of users with an empty cache for different web pages may vary, especially for pages with a high number of active (daily) users. However, we found in our study that regardless of usage patterns, the percentage of page views with an empty cache is always ~20%.

Conclusion: Keep in mind the empty cache user experience. It might be more prevalent than you think!

Posted by Dion Almaer at 8:39 am

4.1 rating from 30 votes


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Just what i wanted to know more about!

I have been working on a project and this was one of the concerns.

Comment by Dougal Matthews — January 5, 2007

Interesting. That sheds new light on the question of file size and JS libraries. A lot of times the answer to concerns about that is “don’t worry about file size- browser cache is your friend.” It still is, just not as much of a friend as I would have expected. And if Yahoo! is seeing this sort of ratio, imagine what the numbers are for all the rest of the sites on the internet that don’t have yahoo!’s massive user base.

Comment by rob — January 5, 2007

How much of these empty cachers are developers or designers that are using the firefox web developer toolbar. I don’t know about everyone else, but many times I am browsing while I am developing (while my cache is turned off) and then the other half of the time I just forget to turn the cache back on. Granted, this doesn’t account for 20% of a web visits, but it does make me curious.

Comment by Daniel — January 5, 2007

Great post. Thanks.
Does this 20% empty cache include “If_Modified_Since” requests also ?.

Comment by Yeskumar — January 5, 2007

Great point, but not surprising though.
IE7 now offering cache cleaning on browser close, and Firefox does that by default.

Comment by Simon Jia — January 5, 2007

These are browser basic concepts.If you are web deveoper you should know there concepts before writing your first hello world program in web.I don’t think this is value added article.But good for beginners.

Comment by Vijaya Bhaskar — January 6, 2007

On the contrary Vijaya, I think there are quite a few misconceptions surrounding caching and even more permutations of browsing environments to consider about the same. So having a look at the experiences of a highly trafficked site is extremely useful and points too many of the other posts here speaking to maximizing caching and http compression etc. We’ve always focused on leveraging the use of the cache during only during the session and if you also build your sites with a similar perspective I can see how you’d find this post to be of no consequence. It should in fact prove that optimizing sites to use caching during the session along with other code and markup optimizations have a will continue to be among the better approaches.

Comment by Frederick Townes — January 7, 2007

I would agree with Frederick. Cache use and policy is very misunderstood. There is an interesting site just promoting this Web developers and it is clear that the world doesn’t buy into it if the servers from one product vendor of corporate USA are correct ( Here it seems if people are even aware of caching they are all about busting them not embracing them in any capacity. Let’s keep hoping this becomes novice info but right now it clearly isn’t.

Comment by Matt Lowell — January 8, 2007

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