Peter Müller

What if it were possible to use content-addressable caching in browsers instead of URL-based caching? The increased cache hits would be highly beneficial, especially for sites depending on 3rd party libraries via a CDN. It turns out this is possible. The subresource integrity specification gives us all we need. But it turns out it's not that simple.

None of the ideas I'm describing here are new, and none of them are concieved by me. I just happened to get this idea, like many others, and tried to get the standards bodies to implement it. This lead to a lot of historical digging because much of the knowledge about this is buried in mailing lists, blog posts that only exist in historical web archives and spec maintainers' heads. I'm writing this post in the hope that next time someone gets this great idea, they won't have to do the same work I just did.

When we develop websites we often take the greatest care that all details are right. People are checking the design, the implementation, the responsiveness, the performance, and hordes of people are clicking all the links so ensure that everything is as it should be. We congratulate each other, high five our team, put our work in production and move on to other things.

However our perfectly crafted website is now all but a snapshot of a distant past. As we move on, the pages stick around and become a part of the ever growing public record of the internet. But even though the site was perfect when concieved it's now in a new state. Decay. From now on things can only get worse.

When presented with the challenges of web performance optimization, or any other kind of manipulation of web sites and assets, it is helpful to have a good set of tools at your disposal. Assetgraph aims to be exactly this. A high level interface for your websites, yet still providing low level interfaces for individual assets. A toolkit that lets you build your own tools that fit very specificly to your individual needs.

I have spoken at lengths about how Assetgraph distinguishes itself from other build tools by not just being another unix tool configuration wrapper. In the following I will assume you have already heard me sing Assetgraphs praises. If you haven't, watch my talk from EmpireJS.

Assetgraph is a node module and this post assumes that you are relatively comfortable writing and executing node scripts. By the end you should have learned enough about Assetgraph to get your hands dirty and write your own tools with it.

If you want to see how easy it is to build tools that filter out unused files, inlines your images or rename files for optimal caching, you are in for a treat!

If you are more into just consuming a well tested out-of-the-box build tool, take a look at assetgraph-builder or its grunt-wrapper grunt-reduce.

NOTE: THIS ARTICLE DESCRIBES ASSETGRAPH VERSION 3, NEWER VERSIONS ARE AVAILABLE.

I attended the Edge Conference in London, for which Andrew Betts should receive high praises.

During the build system panel some remarks were made about the Unix philosophy in response to a question I asked. I did get a counter argument in, but the available time only allowed for tweet size comments, so I don't think I got my point across properly. I'll try to go a bit in depth on my reasoning here.

Web performance these days is non-optional. If your web page is slow, you lose business. Our visitors are an impatient lot, and though they are not actively counting milliseconds, web developers have to, just in order to keep visitors' thoughts away from cat videos and flappy bird.

In our hunt for milliseconds we, the web developers, are going through a great ordeal just to keep up. We are following the 14 rules, we are fighting off marketing's bigger is better and we are setting up automated torture machines for our code. All for the milliseconds, all to keep our visitors' attention.