# Lists

Lists are sets of data used to parameterize [rules](/en/transactional/rules/) without having to edit them on every change. Each list stores only one type of information — customer IDs, merchant IDs, IP addresses, among others.

Keeping data in lists separates operational responsibility (maintaining the items) from technical responsibility (maintaining the rules), reducing the risk of accidental changes to rules.

## Create a list

Under **Settings > Lists > New list**:

1. Choose a name using only letters, numbers, hyphens, and underscores — this name is used as a variable in rules and cannot be changed afterwards (e.g., `quarantined-customers`).
2. Add an optional description.
3. Select the list type. Each list accepts only one type of data.
4. Click **Create list**.

## Add items

Open the desired list and click **Add items**:

1. Enter one item per line. Each item is validated according to the list type.
2. Add an optional description, repeated across all items in the insertion (useful for referencing a support ticket, for example).
3. Optionally, set an expiration in hours. Without an expiration, the item remains until manually removed.

Each list holds up to **10,000 items**. You can add up to **1,000 items per insertion** — to register larger volumes, split the content across multiple insertions.

## View and remove items

Items can be paginated or searched using the search field at the top of the table. To remove, use **⋮ > Remove** on the desired item, or **Remove all items** to clear the list.