# Creating Dictionary Detector
A dictionary detector can detect a specific piece of sensitive data (referred to as a token). The token can be any type of sensitive data like a password, API key, IP address, PII, and so on. You must add the token to a file and then upload the file while creating the dictionary. Nightfall scans your data to check if the token present in the uploaded file exists in your data. If a match is found, it fis flagged as sensitive data exposure.
To create a Dictionary Detector:
1. Navigate to the Detectors section from the left pane.
2. Click **+ Custom Detector** and select **Dictionary**.
3. Enter a name for your custom Detector in the **Name** field.
4. (Optional) Enter a description for the Detector in the **Description** field.
5. Upload or drag and drop the text file which contains a token.
6. (Optional) Select the **Match substrings** check box to match the sub-strings of the text file.
7. Click **Add**.
