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A minimal and opinionated linter for Clojure code that sparks joy.


You don't mind the occasional inline def for debugging, but you would like to get rid of them before making your code public. Also, unnecessary do and let nestings don't really add any value to your life. Let clj-kondo help you tidy your code.


  • inline def warnings
  • obsolete do warnings
  • obsolete let warnings
  • arity errors across namespaces
  • private function call errors

This linter is:

  • compatible with .clj, .cljs and .cljc files
  • build tool and editor agnostic


Under active development, but already useful. None of the code is meant to be exposed as a public API, except the command line interface.

For new features I'd like to focus on things that joker doesn't support yet, so I recommend enabling that one as well.



brew install borkdude/brew/clj-kondo


Install Linuxbrew. Then run:

brew install borkdude/brew/clj-kondo

Manual install

Pre-built binaries are available for linux and MacOS on the releases page.

Running on the JVM


Command line

Lint from stdin:

$ echo '(def x (def x 1))' | clj-kondo --lint -
<stdin>:1:8: warning: inline def

Lint a file:

$ echo '(def x (def x 1))' > /tmp/foo.clj
$ clj-kondo --lint /tmp/foo.clj
/tmp/foo.clj:1:8: warning: inline def

Lint a directory:

$ clj-kondo --lint src
src/clj_kondo/test.cljs:7:1: warning: obsolete do
src/clj_kondo/vars.clj:291:3: error: Wrong number of args (1) passed to clj-kondo.vars/analyze-arities

Lint a project classpath:

$ clj-kondo --lint $(lein classpath)

Project setup

To detect lint errors across namespaces in your project, a cache is needed. To create one, make a .clj-kondo directory in the root of your project. A cache will be created inside of it when you run clj-kondo with the --cache option. Before linting inside your editor, it is recommended to lint the entire classpath to teach clj-kondo about all the libraries you are using, including Clojure and/or ClojureScript itself:

$ clj-kondo --lint <classpath> --cache

Build tool specific ways to get a classpath:

  • lein classpath
  • boot with-cp -w -f
  • clj -Spath

So for lein the entire command would be:

$ clj-kondo --lint $(lein classpath) --cache

Now you are ready to lint single files using editor integration. A simulation of what happens when you edit a file in your editor:

$ echo '(select-keys)' | clj-kondo --lang cljs --cache --lint -
<stdin>:1:1: error: Wrong number of args (0) passed to cljs.core/select-keys

Since clj-kondo now knows about your version of ClojureScript via the cache, it detects that the number of arguments you passed to select-keys is invalid. Each time you edit a file, the cache is incrementally updated, so clj-kondo is informed about new functions you just wrote.

Editor integration

Exit codes

  • 0: no errors or warnings were found
  • 2: more than one warning was found
  • 3: more than one error was found

All other error codes indicate an unexpected error.


This tool uses static analysis on your source code. Therefore it cannot detect all of the issues that a runtime linter can. This tool is written in Clojure and compiles to native code using GraalVM. Any library that is problematic with GraalVM can therefore not be used in this project.



Building from source


This project is inspired by joker. It uses clj.native-image for compiling the project. The parsing of Clojure code relies on rewrite-clj.


Copyright © 2019 Michiel Borkent

Distributed under the EPL License, same as Clojure. See LICENSE.

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