Tree-sitter vs. Language Servers

Summary

21 Jan 2026 I got asked a good question today: what is the difference between Tree-sitter and a language server? I don’t understand how either of these tools work in depth, so I’m just going to explain from an observable, pragmatic point of view. Tree-sitter # Tree-sitter is a parser generator. What this means is that you can hand Tree-sitter a description for a programming language and it will create a program that will parse that language for you. What’s special about Tree-sitter is that it is a.) fast, and b.) can tolerate syntax errors in the input. These two properties make Tree-sitter ideal for creating syntax highlighting engines in text editors. When you’re editing a program, most of the time the program will be in a syntactically invalid state. During that time, you don’t want your colors changing or just outright breaking while you’re typing. Naïve regex-based syntax highlighters frequently suffer from this issue. Tree-sitter also provides a query language where you can make queries against the parse tree. I use this in the Emacs package I’m trying to develop to add Typst support to the Citar citation/bibliography tool: I can ask Tree-sitter to find a particular syntax object; it is safer and more robust than using a regular expression because it can do similar parsing to the Typst engine itself. In short, Tree-sitter provides syntax highlighting that is faithful to how the language implementation parses the program, instead of relying on regular expressions that incidentally come close. Language server # A language server is a program that can analyze a program and report interesting information about that program to a text editor. A standard, called the Language Server Protocol (LSP), defines the kinds of JSON messages that pass between a text editor and the server. The protocol is an open standard; any language and any text editor can take advantage of the protocol to get nice smart programming helps in their system. Language servers can provide informa...