LSP, or Language Server Protocol, is a standardized protocol that enables code editors and development environments to communicate with language-specific tools in a uniform way. The protocol defines how features such as autocompletion, debugging, code navigation, and documentation can be delivered independently of both programming language and editor.
The core idea behind the Language Server Protocol is to separate the editor itself from the logic that understands a particular programming language. Before LSP, each editor would have its own implementation of support for each language, which led to a lot of duplicated work and uneven quality. With LSP, an editor can instead act as a client that sends requests to a so-called language server, which has deep knowledge of the language's syntax, semantics, and rules. Communication between client and server typically takes place via JSON-RPC over standard input/output or sockets.
When a developer writes code, the editor can, via LSP, ask the language server for code completion suggestions, information about symbols, marking syntax errors, or help renaming variables across an entire project. This means that the same language server can be used in many different editors, such as Visual Studio Code, Neovim, Emacs, or IntelliJ-based environments, without the functionality having to be implemented anew each time.
LSP supports a wide range of advanced features, including “go to definition”, “find references”, hover information and diagnostics, which provide warnings and errors directly in the code. The protocol is designed to be extensible, so new capabilities can be added over time without breaking older clients and servers. It has made LSP a living ecosystem with many open source implementations for languages like Python, JavaScript, TypeScript, Rust, Go and C++.
In practice, the Language Server Protocol has had a significant impact on the developer experience. It has lowered the barrier to building great editor tools for new or niche languages and contributed to more consistent functionality across platforms. At the same time, it gives developers the freedom to choose the editor they prefer without compromising on intelligent language tools. LSP can therefore be seen as a central building block in modern software development, where flexibility, reuse and consistency are important principles.