How to install earlier version of mongodb with homebrew?

When trying to install old versions of something with homebrew, it's usually useful to start with brew search packagename, in this case, there's a 2.6 version available under homebrew/versions/mongodb26

So, to install that version:

brew install homebrew/versions/mongodb26

Edit

This answer has certainly become very dated. Take a look at the answer below for a valid way to accomplish this in 2021.

curl -O https://fastdl.mongodb.org/osx/mongodb-osx-x86_64-3.2.12.tgz
tar -zxvf mongodb-osx-x86_64-3.2.12.tgz
mkdir -p mongodb
cp -R -n mongodb-osx-x86_64-3.2.12/ mongodb
export PATH=<mongodb-install-directory>/bin:$PATH #path to the dir created in step 3
mkdir -p /data/db
sudo chown -R $(whoami) /data/
mongod

Note: In September 2019 mongodb was removed from homebrew core, so these instructions have been updated to use mongodb-community instead, installed from the external tap.

If your current installation is still the pre-September mongodb package then you will need to use that name when you unlink, stop, relink and start, on the lines marked with #*# below.

Another option is to simply upgrade away from the deprecated package now.

I already have the latest version of mongo installed, thanks to.

brew tap mongodb/brew

brew install mongodb-community

But I want to switch to the old version sometimes. First, install it:

brew search mongo

brew install [email protected]

Let's stop the current mongodb, if it is running:

brew services stop mongodb/brew/mongodb-community           #*#

# or if you had started it manually

killall mongod

Now I want 3.2 on my PATH instead of the latest:

brew unlink mongodb-community                               #*#

brew link --force [email protected]

(Apparently it needs --force because it is keg-only.)

Now I have 3.2 on my PATH, I can start the test DB:

mongod --version

brew services start mongodb/brew/mongodb-community

# or start your own mongod from the command-line

When I am finished, I can do the reverse to switch back to the latest version:

brew services stop mongodb/brew/mongodb-community

brew unlink [email protected]

brew link mongodb-community                                 #*#

brew services start mongodb/brew/mongodb-community          #*#

And restart again.