Linking MongoDB as a source

The MongoDB connector can link your MongoDB collections to PostHog.

To link MongoDB:

1. Go to the Data pipeline page and the sources tab in PostHog
2. Click New source and select MongoDB
3. Enter your MongoDB connection string. If your connection string doesn't include a database name, enter it in the optional Database name field.
4. Click Next, select the collections you want to sync, as well as the sync method, and then press Import

Tip: MongoDB Atlas SRV connection strings usually omit the database name (e.g., mongodb+srv://user:pass@cluster.mongodb.net/). If yours doesn't include one, fill in the Database name field. A database specified in the connection string (e.g., mongodb+srv://user:pass@cluster.mongodb.net/my_database) takes precedence over this field.

Once the syncs are complete, you can start using MongoDB data in PostHog.

Note: MongoDB data is unstructured so the returned columns are an _id field and a data column that contain the entire document contents. Data fields can be selected with dot notation (e.g. data.field1)

Configuration

Supported tables

The tables available from this source are discovered from your account when you connect it, so the exact list depends on your data. Once connected, you can pick which tables to sync from the sources tab.

Incremental and append-only syncing

MongoDB supports incremental and append-only sync methods. For a field to be available for these sync methods, it must:

1. Have an index — only indexed fields are eligible.
2. Be a supported type — the following BSON types work:
   • date or timestamp
   • int or long
   • double or decimal
   • objectId (only for the _id field)

PostHog infers field types from the first 10,000 documents in the collection, so fields with mixed types may resolve to an unsupported type.

Troubleshooting

No collections found

PostHog connected to MongoDB but reports no collections in the selected database. This usually means one of the following:

• Wrong database in connection string – A connection string ending in /admin or /test connects to an empty system database. Update it to point to the database that holds your data.

• Database name not specified – Atlas mongodb+srv:// strings often omit the database name. Set the Database name field in PostHog to the correct database.

• Missing read permissions – Collection listing is filtered by authorization. Ensure your database user has a read role (such as read or readAnyDatabase) on the target database.

Inbound IP addresses

We use a set of IP addresses to access your instance. To ensure this connector works, add these IPs to your inbound security rules: