# Connecting Locally to MongoDB

You can run your Empirica experiment locally, whilst still connecting it to a cloud MongoDB database.

To do so, you need to [create the database and obtain the URI](https://docsv1.empirica.ly/guides/deploying-my-experiment/database).

## Via the settings file

As explained in the [guide for deploying to MongoDB](https://docsv1.empirica.ly/deploying-my-experiment/database#how-do-i-connect-my-app-to-mongodb-atlas), you will need to add these elements to your settings file:

```
    "galaxy.meteor.com": {
        "env": {
            "MONGO_URL": "mongodb+srv://<read&write username>:<read&write password>@<connection>/<database name>?retryWrites=true&w=majority",
            "MONGO_OPLOG_URL": "mongodb+srv://<oplog username>:<oplog password>@<connection>/local"
        }
    },
```

Fill in the <> parts with the appropriate elements.

Now you can run your app with:

```
meteor --settings <name of settings file>
```

{% hint style="info" %}
This might not always work for connecting locally to your MongoDB. The method below is more reliable.
{% endhint %}

## Via the command line

According to your OS, follow the instructions below to connect to your MongoDB via the command line.

{% tabs %}
{% tab title="Mac, Linux, Windows with WSL" %}
Run this command with the URI you have obtained but without the `?retryWrites=true&w=majority`

```
MONGO_URL=<MongoDB URI> meteor
```

{% endtab %}

{% tab title="Windows without WSL" %}
Create a `.bat` file (e.g., `start.bat`). **These files allow you to run multiple commands on Windows. Do not run commands you are not comfortable with or not convinced they are secure.**

Make sure that you have `*.bat` in your `.gitignore` because this file will contain sensitive information (your access to the database) and you don't want it to be sent to your repository.\
\
Add the following commands to the file with the URI you have obtained but without the `?retryWrites=true&w=majority`:

```
SET MONGO_URL=<MongoDB URI>
meteor
```

Run the file in the command line (e.g., `.\start.bat` ).
{% endtab %}
{% endtabs %}