Resolves the given hostname to a DNS record.

This is an asynchronous function that returns a Promise.


let resolving = browser.dns.resolve(
  hostname,    // string
  flags        // array of string



string. The hostname to resolve.

flags Optional

array of string. Flags to modify the way the hostname is resolved. Any omitted flags default to false. You can pass zero or more of the following flags:

  • "allow_name_collisions": Allow name collision results which are normally filtered out.
  • "bypass_cache": Suppresses the internal DNS lookup cache.
  • "canonical_name": The canonical name of the specified host will be queried.
  • "disable_ipv4": Only IPv6 addresses will be returned.
  • "disable_ipv6": Only IPv4 addresses will be returned.
  • "disable_trr": Do not use the Trusted Recursive Resolver (TRR) for resolving the host name. A TRR enables resolving of host names using a dedicated DNS-over-HTTPS server.
  • "offline": Only literals and cached entries will be returned.
  • "priority_low": The request is given lower priority. If "priority_medium" is also given, the query is given medium priority.
  • "priority_medium": The request is given medium priority. If "priority_low" is also given, the query is given medium priority.
  • "speculate": Indicates that the request is speculative. Speculative requests return errors if prefetching is disabled by the browser's configuration.

Return value

A Promise that will be fulfilled with a DNSRecord object. This object can contain the following properties:


array of string. The IP addresses associated with this DNS record.


string. The canonical name for this record. This is only included in the response if the "canonical_name" flag was passed to resolve().


boolean: true if the record was retrieved using a Trusted Recursive Resolver (TRR).

Browser compatibility

BCD tables only load in the browser


function resolved(record) {

let resolving = browser.dns.resolve("example.com");

// > e.g. Array [ "" ]

Bypass the cache, and ask for the canonical name:

function resolved(record) {

let resolving = browser.dns.resolve("developer.mozilla.org",
                                   ["bypass_cache", "canonical_name"]);

// > e.g. xyz.us-west-2.elb.amazonaws.com
// > e.g. Array [ "", "" ]