Step by Step connecting Cosmos DB Emulator with a Mongo DB GUI (Robo3T)

     Cosmos DB Emulator supports Mongo DB API. That means you can use Emulator to develop Mongo DB solutions locally. To make it work; you need to enable mongo endpoint first. If you have a custom port, you can override the default Mongo DB port too. To do that, you need to run the Emulator with different parameters. First, you need to start the windows command prompt and change the current directory to Emulator's directory. Cosmos Db Emulator default path is C:\Program Files\Azure Cosmos DB Emulator

     Next, we need to use the parameter "/EnableMongoDbEndpoint" to open the MongoDB endpoint. If you don't specify a port, it will use the default port which is 10250. You can override the port by using the parameter "/MongoPort". I have one more important tip for you if you already have data in your Emulator. In my case, I run Emulator with SQL API and I already have some data in it. If I try to run the Emulator with different API like MongoDB, Emulator will remove all the current data because it uses the same path to store data for MongoDB. If you don't want to lose your data, you can use the parameter "/DataPath" to store new data in different path.

     You should be ready to connect your local Cosmos DB Emulator with a MongoDB Client now. I will use Robo3T to connect my local Cosmos DB Emulator's MongoDB engine. I need to setup the connection first. Easiest way to setup the connection is; copy the MongoDB connection string from the Emulator's QuickStart tab.

     Paste it to the textbox in the bottom of Connection tab. Then click on From SRV button to configure connection. Test the connection to be sure that you can connect before you save it to use it later. If you are having problems with the connections, check if you mistype any parameters when you started the Cosmos Db Emulator. For some reason, if you mistype any parameters, Emulator does not throw any errors and Emulator starts in SQL API mode.

     If all worked fine you should be able to connect to Cosmos DB Emulator as Mongo DB and start to use Robo3T manage data in Cosmos DB Emulator. As you can see in the following screenshot, I have connected to Azure Cosmos DB Emulator's Mongo DB API. Robo 3T believes I connected to a regular Mongo DB.