PHP is know for being very leaky about being PHP (and since PHP + ecosystem have a bad history of CVEs, being leaky about being PHP is not cool).
Java/Kotlin/Go/Rust/Ruby/Python/JS/TS are a lot less leaky about what language the server-side is written in. Usually the webserver used advertises itself name and in a server string, but it is considered bad practice and thus often switched off.
Reading "php" extensions in paths is a clear giveaway, so are "htm" extensions for microsoft products. Tools usually guess the language/framework based on some of these giveaways and the better the tools the less this is evident.
I jut checked some web apps I worked on, and only the one I last touched 10+ years ago is detected with buildwith.com; it's a Rails site.
All the Java/Kotlin/Rust/Hasura+Elm apps I worked on since are now shown as "Nginx" (the rev proxy in front of it).
Java/Kotlin/Go/Rust/Ruby/Python/JS/TS are a lot less leaky about what language the server-side is written in. Usually the webserver used advertises itself name and in a server string, but it is considered bad practice and thus often switched off.
Reading "php" extensions in paths is a clear giveaway, so are "htm" extensions for microsoft products. Tools usually guess the language/framework based on some of these giveaways and the better the tools the less this is evident.
I jut checked some web apps I worked on, and only the one I last touched 10+ years ago is detected with buildwith.com; it's a Rails site.
All the Java/Kotlin/Rust/Hasura+Elm apps I worked on since are now shown as "Nginx" (the rev proxy in front of it).