Client request

These variables describe the HTTP request received by Fastly.

Device detection

Fastly exposes a number of VCL variables describing the client hardware and software based on known User-Agent strings. The data is automatically updated on a regular basis.

The data in these variables is based on mapping client-provided User-Agent headers to a third-party dataset owned and provided by DeviceAtlas. Fastly periodically updates the dataset to have the most recent Device Atlas data, but we cannot guarantee its accuracy.

WARNING: Device information from DeviceAtlas, including data streamed by our log streaming service, may be used only in connection with your use of Fastly services. Use of DeviceAtlas data for any other purpose requires a license from Afilias Technologies Ltd, the supplier of DeviceAtlas.

Presence of data

It's possible for data to be not known for a particular User-Agent. When not present, numerical variables are set to -1, booleans are set false, and strings are set to the empty string.

It's possible to distinguish data being not known from data being explicitly set false by making use of the client.identified variable. client.identified is set when all features are identified, and so a false value for a property can be seen to be meaningful.

To find out more about variables that provide device vendor, model, and manufacturer details, contact your Fastly account manager or sales representative, or contact