DNS

Structure

{
  "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
`rules`	List of DNS Rule
`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

Deprecated in sing-box 1.14.0

independent_cache is deprecated and will be removed in sing-box 1.14.0, check Migration.

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

cache_capacity

Since sing-box 1.11.0

LRU cache capacity.

Value less than 1024 will be ignored.

optimistic

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.

{
  "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

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.