CIDER is the Clojure(Script) Interactive Development Environment that Rocks!

CIDER extends Emacs with support for interactive programming in Clojure. The features are centered around cider-mode, an Emacs minor-mode that complements clojure-mode. While clojure-mode supports editing Clojure source files, cider-mode adds support for interacting with a running Clojure process for compilation, debugging, definition and documentation lookup, running tests and so on.

CIDER is the successor to the now deprecated combination of using SLIME + swank-clojure for Clojure development.

If you like the project, please consider supporting its ongoing development.


CIDER aims to provide an interactive development experience similar to the one you'd get when programming in Emacs Lisp, Common Lisp (with SLIME or Sly), Scheme (with Geiser) and Smalltalk.

Programmers are expected to program in a very dynamic and incremental manner, constantly re-evaluating existing Clojure definitions and adding new ones to their running applications. You never stop/start a Clojure application while using CIDER - you're constantly interacting with it and changing it.

You can find more details about the typical CIDER workflow in the Interactive Programming section. While we're a bit short on video tutorials, you can check out this tutorial about SLIME to get a feel about what do we mean by an "Interactive Development Environment". There are plenty of differences between CIDER and SLIME, but the core ideas are pretty much the same (and SLIME served as the principle inspiration for CIDER).

CIDER's built on top of nREPL, the Clojure networked REPL server.

CIDER's basic architecture looks something like this:

Clojure code gets executed by an nREPL server. CIDER sends requests to the server and processes its responses. The server's functionality is augmented by additional nREPL middleware, designed specifically to address the needs of an interactive development environment like CIDER. Much of the middleware we developed for CIDER is editor-agnostic and is being used by other Clojure development environments as well (e.g. vim-fireplace & CCW).

CIDER packs plenty of features. Here are some of them (in no particular order):

CIDER Screenshot