Programs using HTTP typically report a user agent to avoid being blocked. User agent metadata help the server know user client statistics.

CMake’s HTTP user agent is like

curl/<curl version>

as seen with CMake script.

Some servers may block CMake download traffic such as file(DOWNLOAD …). A web browser from the same computer may work–this is a symptom of server user agent blocking. This script demonstrates setting a custom HTTP user agent to get around servers that block non-allow-listed user agents.