At Google, Chris Zacharias spent his "20 percent time" building a new version of YouTube just for places with slow internet connections. It was called Feather, and the basic idea was to build a YouTube page that contained no more than 100 kilobytes of data, so that it could quickly load on machines in developing countries and other places where internet pipes were painfully narrow.

In the end, Feather worked well enough, bringing YouTube to many places that had never used the world's most popular video site. But building the machine was far more difficult than it should have been, mainly because Zacharias didn't have an easy way of shrinking the still thumbnail images that represented each YouTube video. These still images – the pictures you see before you hit "play" on a YouTube video – had been created for relatively fast internet connections, so they were quite large. In building Feather, Zacharias wanted to shrink them down to something smaller, but that was an almost impossible task. This was 2010, and YouTube already spanned billions of videos.

"We just couldn't crunch those images down to a smaller size," Zacharias remembers. "It would have taken a significant amount of Google's entire processing power just to do that."

That's when imgix was born. Zacharias soon left Google and YouTube to found the San Francisco startup, which has built a web service for instantly re-sizing, re-cropping, and re-formatting images. Had imgix been available when he was building YouTube Feather, Zacharias could have shrunk those thumbnails in real-time, as people were visiting the video site, and many companies are now using imgix in similar ways, including apartment rental website Zillow, internet radio service 8tracks, and Swiftype, which provides a text search service for sites across the web.

>'We just couldn't crunch those images down to a smaller size. It would have taken a significant amount of Google's entire processing power just to do that' Chris Zacharias

Imgix is an application programming interface, or API. Basically, this means that when you're building a website, you can include code that plugs it into the imgix service. You point the service at all the photos that appear on your website, and then, when someone visits the site, imgix will deliver the appropriate photos and, in need be, reformat or resize them. If someone visit your site with an Apple iPad, the service can instantly reformat an image for the tablet's "Retina" display.

At Zillow, for instance, individual web surfers will upload photos of apartments they wish to rent out, and imgix is charged with formatting these photos when others browse the site for places they'd like to stay. "We had explored building our own service for resizing all those photos," says Kunal Shah, of Zillow, "but Chris has already done it, and eventually, we switched everything to the service."

imgix originally ran atop Amazon's EC2 service, which provides instant access to processing power over the net. But Zacharias and his fellow engineers – co-founder Jeremy Larkin, David Birdsong, and Jack Angers – have since moved the service into their own data centers, setting up a fleet of machines that rely heavily on graphics processing units, or GPUs, the chips that traditionally crunched graphics on your desktop and notebook PCs.

In fact, they began building this data center operation with ordinary Mac Mini PCs – "We just wanted relatively cheap machines with good GPUs," Zacharias says. "We would just walk into one Apple store after another and buy them out" – though they're now moving towards beefier servers and GPUs, after securing additional funding (over $5 million to date).

Chris Zacharias. Photo: Alex Washburn / Wired Alex Washburn

The operation is just one of an ever growing number of online services that let outsource part of your web infrastructure. Cloud services from the likes of Amazon and Rackspace give you raw processing power for running almost any software, but countless other operations are serving up more specialized infrastructure services, ranging from the sort of image-processing provided by imgix to data analysis services from the likes of Google and startup Keen IO.

At the same time, imgix is part of the movement towards GPUs in the modern data center, with everyone from Google to Salesforce.com harnessing the power of these graphics chips, which are suited to almost any task that involves processing large amounts of data in parallel. The San Francisco startup is just four people strong, running its operation out of a tiny loft above a print shop on Howard Street, but it has built up an infrastructure capable of crunching images for even the largest of websites.

The aim, says Zacharias, is to build a graphics engine for the internet as a whole – a service that can handle all sorts of image processing for virtually any website. This would include videos and games as well as still images. "Much like Dropbox is building a massive hard drive for the internet," he says, "we're building a graphics card for the internet."