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…

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…

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…

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…

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…

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…

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…