--- title: List overview: Adapter that performs whitelist or blacklist checks location: https://istio.io/docs/reference/config/adapters/list.html layout: protoc-gen-docs number_of_entries: 2 ---

The `list` adapter makes it possible to perform simple whitelist or blacklist checks. You can configure the adapter with the list to check, or you can point it to a URL from where the list should be fetched. Lists can be simple strings, IP addresses, or regex patterns.

## Params

Configuration format for the `list` adapter.

Field | Type | Description
--- | --- | ---
`providerUrl` | `string` | Where to find the list to check against. This may be ommited for a completely local list.
`refreshInterval` | `google.protobuf.Duration` | Determines how often the provider is polled for an updated list
`ttl` | `google.protobuf.Duration` | Indicates how long to keep a list before discarding it. Typically, the TTL value should be set to noticeably longer (> 2x) than the refresh interval to ensure continued operation in the face of transient server outages.
`cachingInterval` | `google.protobuf.Duration` | Indicates the amount of time a caller of this adapter can cache an answer before it should ask the adapter again.
`cachingUseCount` | `int32` | Indicates the number of times a caller of this adapter can use a cached answer before it should ask the adapter again.
`overrides` | `string[]` | List entries that are consulted first, before the list from the server
`entryType` | `Params.ListEntryType` | Determines the kind of list entry and overrides.
`blacklist` | `bool` | Whether the list operates as a blacklist or a whitelist.

## Params.ListEntryType

Determines the type of list that the adapter is consulting.

Name | Description
--- | ---
`STRINGS` | List entries are treated as plain strings.
`CASE_INSENSITIVE_STRINGS` | List entries are treated as case-insensitive strings.
`IP_ADDRESSES` | List entries are treated as IP addresses and ranges.
`REGEX` | List entries are treated as re2 regexp. See here for the supported syntax.