XSLT
XSLT is a declarative programming language used for transforming XML documents. Its main use is to manipulate XML data and generate new structured documents, such as HTML, PDF, or different XML formats.
Hello, world code example:
Hello world!
Popularity: Less than 1% of developers are using or have used this language.*
*According to StackOverflow's 2023 survey.
Repositories on GitHub: 27,298