HTTP Heuristic Caching (Missing Cache-Control and Expires Headers) Explained

Have you ever wondered why WebPageTest can sometimes show that a repeat view loaded with less bytes downloaded, while also triggering warnings related to browser caching? It can seem like the test is reporting an issue that does not exist, but in fact it’s often a sign of a more serious issue that should be investigated. Often the issue is not the lack of caching, but rather lack of control over how your content is cached.

Adoption of HTTP Security Headers on the Web

Over the past few weeks the topic of security related HTTP headers has come up in numerous discussions – both with customers I work with as well as other colleagues that are trying to help improve the security posture of their customers. I’ve often felt that these headers were underutilized, and a quick test on Scott Helme’s excellent securityheaders.io site usually proves this to be true. I decided to take a deeper look at how these headers are being used on a large scale.

Cache Control Immutable – A Year Later

In January 2017, Facebook wrote about a new Cache-Control directive – immutable – which was designed to tell supported browsers not to attempt to revalidate an object on a normal reload during it’s freshness lifetime. Firefox 49 implemented it, while Chrome went ahead with a different approach by changing the behavior of the reload button. Additionally it seems that WebKit has also implemented the immutable directive since then.

Measuring the Performance of Firefox Quantum with RUM

On Nov 14th, Mozilla released Firefox Quantum. On launch day, I personally felt that the new version was rendering pages faster and I heard anecdotal reports indicating the same. There have also been a few benchmarks which seem to show that this latest Firefox version is getting content to screens faster than its predecessor. But I wanted to try a different approach to measurement.

Exploring Relationships Between Performance Metrics in HTTP Archive Data

I thought it would be interesting to explore how some of the page metrics we use to analyze web performance compare with each other. In the HTTP Archive “pages” table, metrics such as TTFB, renderStart, VisuallyComplete, onLoad and fullyLoaded are tracked. And recently some of the newer metrics such as Time to Interactive, First Meaningful Paint, First Contentful paint, etc exist in the HAR file tables.

Tracking Page Weight Over Time

As of July 2017, the “average” page weight is 3MB. @Tammy wrote an excellent blog post about HTTP Archive page stats and trends. Last year @igrigorik published an analysis on page weight using CDF plots. And of course, we can view the trends over time on the HTTP Archive trends page. Since this is all based on HTTP Archive data, I thought I’d start a thread here to continue the discussion on how to gauge the increase in page weight over time.

Pagination


© 2020 Paul Calvano. All rights reserved.

Powered by Hydejack v9.0.2