What attracts researchers starting from the 60s till nowadays? What is studied in university by engineers in computer science and then successfully forgotten? What is at the heart of the compilers used daily by any software developer? Parsers! From a practical point of view using a small pill of theory, this session will bring lights on questions like: if there is so many parser-generators based on formal theory, then why javac, GCC and Clang are all hand-written? And how we, insiders of the world of parsing, do this at SonarSource for languages like Java, C/C++, C#, JavaScript, Python, COBOL?