You appear to be offline. Some site functionality may not work.
Sign Up

Fastly Blog

Andrew Betts

The headers we want

Manipulating HTTP headers is one of the most common things that Fastly customers do. Using the right combination of headers is one of the best things you can do for the security of your site,…

The headers we don't want

HTTP headers are an important way of controlling how caches and browsers process your web content. But many are used incorrectly or pointlessly, which adds overhead at a critical time in the loading of your…

Clearing cache in the browser

Caching assets in the browser is the most common and most obvious way to improve front end performance. But at some point every developer accidentally makes a bad release of an asset with a long…

Understanding the Vary header in the browser

Browsers need to understand and respond to Vary rules, and the way they do this is different from the way Vary is treated by CDNs. In this post, Principal Developer Advocate Andrew Betts explores the…

Diff at the edge with serverless cloud functions

Requesting the difference between two previously cached files — using just a CDN configuration and a serverless cloud compute function — is a great example of exploiting edge and serverless compute services to make your…

Server-sent events with Fastly

Server-sent events allow web servers to push real-time event notifications to the browser on a long-lived HTTP response. It’s a beautiful part of the web platform that’s severely underused by websites, and whether it’s flight…

Getting the most out of Vary with Fastly

You can use the Vary response header in creative ways, including A/B testing and internationalization. At the same time, many people still use Vary badly or misunderstand what it does; in this post, we’ll provide…