The canonical way to install CIDER is via `package.el` (Emacs's built-in package
manager), but plenty of other options exist (see the
[wiki](https://github.com/clojure-emacs/cider/wiki/Installation)).

## Prerequisites

You'll need to have Emacs installed (preferably the latest stable
release). If you're new to Emacs you might want to go through
[the guided tour of Emacs](https://www.gnu.org/software/emacs/tour/index.html)
and the built-in tutorial (just press <kbd>C-h t</kbd>).

CIDER officially supports Emacs 24.4+, Java 7+ and Clojure(Script) 1.7+.
CIDER 0.10 was the final release which supported Java 6 and Clojure 1.5 and 1.6.

You'll also need a recent version of your favorite build tool (Leiningen, Boot
or Gradle) to be able to start CIDER via `cider-jack-in`. Generally it's a good
idea to use their latest stable versions.

**CIDER does not support ClojureCLR.**

## Installation via package.el

CIDER is available on the two major `package.el` community
maintained repos -
[MELPA Stable](http://stable.melpa.org)
and [MELPA](http://melpa.org).

You can install CIDER with the following command:

<kbd>M-x package-install [RET] cider [RET]</kbd>

or by adding this bit of Emacs Lisp code to your Emacs initialization file
(`.emacs` or `init.el`):

```el
(unless (package-installed-p 'cider)
  (package-install 'cider))
```

If the installation doesn't work try refreshing the package list:

<kbd>M-x package-refresh-contents [RET]</kbd>

Keep in mind that MELPA packages are built automatically from
the `master` branch, meaning bugs might creep in there from time to
time. Never-the-less, installing from MELPA is a reasonable way of
obtaining CIDER, as the `master` branch is normally quite stable
and serious regressions there are usually fixed pretty quickly.

Generally, users of the non-adventurous kind are advised to stick
with the stable releases, available from MELPA Stable.
In Emacs 24.4+, you can pin CIDER to always use MELPA
Stable by adding this to your Emacs initialization:

```el
(add-to-list 'package-pinned-packages '(cider . "melpa-stable") t)
```

**CIDER has dependencies (e.g. `queue` & `seq`) that are only available in the
  [GNU ELPA repository](https://elpa.gnu.org/). It's the only package repository
  enabled by default in Emacs and you should not disable it!**

## CIDER's nREPL middleware

Much of CIDER's functionality depends on the presence of CIDER's own
[nREPL middleware](https://github.com/clojure-emacs/cider-nrepl). Starting with version 0.11, When `cider-jack-in` (<kbd>C-c M-j</kbd>) is
used, CIDER takes care of injecting it and its other dependencies.

**`profiles.clj` or `profile.boot` don't need to be modified anymore for the above use case!**

If you don't want `cider-jack-in` to inject dependencies automatically, set
`cider-inject-dependencies-at-jack-in` to `nil`. Note that you'll have to setup
the dependencies yourself (see the section below), just as in CIDER 0.10 and older.

CIDER can also inject a Clojure dependency into your project, which is useful,
for example, if your project defaults to an older version of Clojure than that
supported by the CIDER middleware. Set `cider-jack-in-auto-inject-clojure`
appropriately to enable this.

If a standalone REPL is preferred, you need to invoke `cider-connect` (instead
of `cider-jack-in`) and you'll need to manually add the dependencies to your
Clojure project (explained in the following section).

### Setting up a standalone REPL

#### Using Leiningen

Use the convenient plugin for defaults, either in your project's
`project.clj` file or in the :repl profile in `~/.lein/profiles.clj`.

```clojure
:plugins [[cider/cider-nrepl "x.y.z"]]
```

A minimal `profiles.clj` for CIDER would be:

```clojure
{:repl {:plugins [[cider/cider-nrepl "0.14.0"]]}}
```

**Be careful not to place this in the `:user` profile, as this way CIDER's
middleware will always get loaded, causing `lein` to start slower.  You really
need it just for `lein repl` and this is what the `:repl` profile is for.**

#### Using Boot

Boot users can configure the tool to include the middleware automatically in
all of their projects using a `~/.boot/profile.boot` file like so:

```clojure
(require 'boot.repl)

(swap! boot.repl/*default-dependencies*
       concat '[[cider/cider-nrepl "0.14.0"]])

(swap! boot.repl/*default-middleware*
       conj 'cider.nrepl/cider-middleware)
```

For more information visit [boot-clj wiki](https://github.com/boot-clj/boot/wiki/Cider-REPL).

### Using embedded nREPL server

If you're embedding nREPL in your application you'll have to start the
server with CIDER's own nREPL handler.

```clojure
(ns my-app
  (:require [clojure.tools.nrepl.server :as nrepl-server]
            [cider.nrepl :refer (cider-nrepl-handler)]))

(defn -main
  []
  (nrepl-server/start-server :port 7888 :handler cider-nrepl-handler))
```

It goes without saying that your project should depend on `cider-nrepl`.

***

`x.y.z` should match the version of CIDER you're currently using (say `0.14.0`).
For snapshot releases of CIDER you should use the snapshot of the plugin as well
(say `0.14.0-SNAPSHOT`).