linter
A tool that checks code against written rules
A linter is a program that reads source code without running it. It reports anything that breaks rules the team has chosen. The rules can cover style, safety or consistency. Developers usually run it automatically when they save or submit work. Each report says which line broke which rule, so it can be fixed before the code reaches customers.
Think of it as
Like a spell checker for code: it underlines problems as you write, before anyone else reads the document.