index.md

---

title: dns.resolve()
slug: Mozilla/Add-ons/WebExtensions/API/dns/resolve
page-type: webextension-api-function
tags:
  - API
  - Add-ons
  - DNS
  - Extensions
  - Method
  - Reference
  - WebExtensions
  - resolve
browser-compat: webextensions.api.dns.resolve

---

{{AddonSidebar()}}

Resolves the given hostname to a DNS record.

This is an asynchronous function that returns a Promise.

Syntax

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

Parameters

• hostname

  • : string. The hostname to resolve.

• flags {{optional_inline}}

  • : 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:

• addresses

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

• canonicalName

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

• isTRR

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

Browser compatibility

{{Compat}}

Examples

function resolved(record) {
  console.log(record.addresses);
}

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

// > e.g. Array [ "73.284.240.12" ]

Bypass the cache, and ask for the canonical name:

function resolved(record) {
  console.log(record.canonicalName);
  console.log(record.addresses);
}

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

// > e.g. xyz.us-west-2.elb.amazonaws.com
// > e.g. Array [ "78.18.187.134", "34.79.135.234" ]

{{WebExtExamples}}