Forget JavaScript, It’s Time for Browsers to Speed Up Images

The average webpage is now 1.2 megabytes and around 60 percent of that rather large payload comes from images. That’s a lot of data, whether you’re handling images responsively or just trying to speed up a desktop site.

You might think, if images are the bulk of what your browser is downloading, that browsers would be working hard to speed up the image downloads, perhaps trying alternate, space-saving image formats, but you’d be wrong.

You might also think that, as Google’s Ilya Grigorik writes, “innovating on better image formats would be a top agenda item” for the web. But again you’d be wrong. The web is still using the same image formats it’s been using virtually since the first images appeared online.

Grigorik thinks it’s high time that changed and we agree.

In a recent post looking at what it would take to deploy new image formats on the web, he writes, “if we really want to make an impact on web performance, then image formats is the place to do it… there is absolutely no reason why we shouldn’t have dozens of specialized formats, each tailored for a specific case and type of image.”

Of course no web developer wants to deal with dozens of specialized image formats. Nor should they need to — that’s a job for servers. “In a world with dozens of image formats,” continues Grigorik, “the human solution does not scale — read, markup does not scale… whereas computers are fantastic at doing exactly the kind of optimization work required to solve the problem.”

Grigorik isn’t alone in calling for new image formats, nor is he the first to suggest handing these tasks off to the server. Developer and responsive images proponent Matt Wilcox has argued for a similar solution, as have others.

The basic premise of these arguments is that deciding which image to serve up to which device and browser should be a server-side problem. And in fact there’s already a way to solve this problem with HTTP headers, namely the Accepts header, which tells the server which image formats the browser supports. Based on that information the server could then “re-encode, recompress, resize, strip unnecessary metadata and deliver the optimal format.”

The problem is that web browsers (with the exception of Opera) don’t actually send useful information in the Accepts header.

Thus, the first step in creating a server-side solution for smaller images is to get other browsers to send useful Accepts headers.

The Accepts header isn’t a magic bullet by any means, but it’s a problem that’s not hard to solve provided browser makers prioritize it. But to really get server side image solutions working the web would also need new server tools (fortunately, several already exist). There are other stumbling blocks as well. Grigorik addresses half a dozen potential problems and objections that you can read through in his post.

Even if browser makers come around to the idea and do start improving Accepts headers, bringing better image formats to the web is going to be an uphill battle. But Grigorik is determined to chase the idea. “Some uphill battles are worth fighting,” he writes in a comment, “I think this a good one. Wish me luck.”