---
icon: material/alert-decagram
---

!!! quote "Changes in sing-box 1.14.0"

    :material-delete-clock: [independent_cache](#independent_cache)  
    :material-plus: [optimistic](#optimistic)

!!! quote "Changes in sing-box 1.12.0"

    :material-decagram: [servers](#servers)

!!! quote "Changes in sing-box 1.11.0"

    :material-plus: [cache_capacity](#cache_capacity)

# DNS

### Structure

```json
{
  "dns": {
    "servers": [],
    "rules": [],
    "final": "",
    "strategy": "",
    "disable_cache": false,
    "disable_expire": false,
    "independent_cache": false,
    "cache_capacity": 0,
    "optimistic": false, // or {}
    "reverse_mapping": false,
    "client_subnet": "",
    "fakeip": {}
  }
}

```

### Fields

| Key      | Format                          |
|----------|---------------------------------|
| `server` | List of [DNS Server](./server/) |
| `rules`  | List of [DNS Rule](./rule/)     |
| `fakeip` | :material-note-remove: [FakeIP](./fakeip/) |

#### final

Default dns server tag.

The first server will be used if empty.

#### strategy

Default domain strategy for resolving the domain names.

One of `prefer_ipv4` `prefer_ipv6` `ipv4_only` `ipv6_only`.

#### disable_cache

Disable dns cache.

Conflict with `optimistic`.

#### disable_expire

Disable dns cache expire.

Conflict with `optimistic`.

#### independent_cache

!!! failure "Deprecated in sing-box 1.14.0"

    `independent_cache` is deprecated and will be removed in sing-box 1.14.0, check [Migration](/migration/#migrate-independent-dns-cache).

Make each DNS server's cache independent for special purposes. If enabled, will slightly degrade performance.

#### cache_capacity

!!! question "Since sing-box 1.11.0"

LRU cache capacity.

Value less than 1024 will be ignored.

#### optimistic

!!! question "Since sing-box 1.14.0"

Enable optimistic DNS caching. When a cached DNS entry has expired but is still within the timeout window,
the stale response is returned immediately while a background refresh is triggered.

Conflict with `disable_cache` and `disable_expire`.

Accepts a boolean or an object. When set to `true`, the default timeout of `3d` is used.

```json
{
  "enabled": true,
  "timeout": "3d"
}
```

##### enabled

Enable optimistic DNS caching.

##### timeout

The maximum time an expired cache entry can be served optimistically.

`3d` is used by default.

#### reverse_mapping

Stores a reverse mapping of IP addresses after responding to a DNS query in order to provide domain names when routing.

Since this process relies on the act of resolving domain names by an application before making a request, it can be
problematic in environments such as macOS, where DNS is proxied and cached by the system.

#### client_subnet

!!! question "Since sing-box 1.9.0"

Append a `edns0-subnet` OPT extra record with the specified IP prefix to every query by default.

If value is an IP address instead of prefix, `/32` or `/128` will be appended automatically.

Can be overridden by `servers.[].client_subnet` or `rules.[].client_subnet`.