Can I perform a DNS lookup hostname to IP address using client-side Javascript

Question

I would like to use client-side Javascript to perform a DNS lookup  hostname to IP address  as seen from the client s computer  Is that possible

User · Answer

I am aware this is an old question but my solution may assist others.

I find that the JSON(P) services which make this easy do not last forever but the following JavaScript works well for me at the time of writing.

<script type="text/javascript">function z (x){ document.getElementById('y').innerHTML=x.query }</script>
<script type='text/javascript' src='http://ip-api.com/json/zero.eu.org?callback=z'></script>

The above writes my server's IP on the page it is located but the script can be modified to find any IP by changing 'zero.eu.org' to another domain name. This can be seen in action on my page at: http://meon.zero.eu.org/

User · Answer

Maybe I missed the point but in reply to NAVY guy here is how the browser can tell you the  requestor s  IP address  albeit maybe only their service provider    Place a script tag in the page to be rendered by the client that calls  has src pointing to  another server that is not loaded balanced  I realize that this means you need access to a 2nd server but hosting is cheap these days and you can set this up easily and cheaply    This is the kind of code that needs to be added to client page     On the other server  someServerIown  you need to have the ASP  ASPX or PHP page that   ----- contains server code like this     lt    Response Write  var clientipaddress       amp  Request ServerVariables  REMOTE ADDR    amp               without the outside dbl quotes  -    ---- and writes this code back to script tag      var clientipaddress    178 32 21 45     This effectively creates a Javascript variable that you can access with Javascript on the page no less   Hopefully  you access this var and write the value to a form control ready for sending back   When the user posts or gets on the next request your Javascript and or form sends the value of the variable that the  otherServerIown  has filled in for you  back to the server you would like it on   This is how I get around the dumb load balancer we have that masks the client IP address and makes it appear as that of the Load balancer      dumb     dumb dumb dumb   I haven t given the exact solution because everyone s situation is a little different  The concept is sound  however  Also  note if you are doing this on an HTTPS page your  otherServerIOwn  must also deliver in that secure form otherwise Client is alerted to mixed content  And if you do have https then make sure ALL your certs are valid otherwise client also gets a warning   Hope it helps someone  Sorry  it took a year to answer contribute   -

User · Answer

My version is like this   php on my server    lt  php     header  content-type  application json  charset utf-8          data   json encode   SERVER  REMOTE ADDR            callback   filter input INPUT GET                     callback                    FILTER SANITIZE STRING                    FILTER FLAG ENCODE HIGH FILTER FLAG ENCODE LOW       echo  callback          data           gt    jQuery on the page   var self   this    ajax       url  this url    getip php       data  null      type   GET       crossDomain  true      dataType   jsonp      done  function  json          self ip   json         It works cross domain  It could use a status check  Working on that

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I know this question was asked a very long time ago  but I figured I d offer a more recent answer  DNS over HTTPS  DoH  You can send DNS queries over HTTPS to DNS resolvers that support it  The standard for DOH is described in RFC 8484  This is a similar thing to what all the other answers suggest  only that DoH is actually the DNS protocol over HTTPS  It s also a  quot proposed quot  Internet standard and it s becoming quite popular  For example  some major browsers either support it or have plans to support it  Chrome  Edge  Firefox   and Microsoft is in the process of building it into their operating system  One of the purposes of DoH is   allowing web applications to access DNS information via existing browser APIs in a safe way consistent with Cross Origin Resource Sharing  CORS   There s an open source tool made especially for doing DNS lookups from web applications called dohjs  It does DNS over HTTPS  DoH  wireformat queries as described in RFC 8484  It supports both GET and POST methods  Full disclosure  I am a contributor to dohjs  Another JavaScript library with similar features is found here - https   github com sc0Vu doh-js-client  I haven t used this one personally  but I think it would work client side as well  DNS over HTTPS JSON APIs If you don t want to bother with DNS wireformat  both Google and Cloudflare offer JSON APIs for DNS over HTTPS   Google s endpoint  https   dns google resolve  Google s JSON API docs  https   developers google com speed public-dns docs doh json Cloudflare s endpoint  https   cloudflare-dns com dns-query  Cloudflare s JSON API docs  https   developers cloudflare com 1 1 1 1 dns-over-https json-format   Example Javascript code to lookup example com with Google s JSON DOH API  var response   await fetch  https   dns google resolve name example com    var json   await response json    console log json    Examples from the RFC for DOH GET and POST with wireformat Here are the examples the RFC gives for both GET and POST  see https   tools ietf org html rfc8484 section-4 1 1   GET example   The first example request uses GET to request  quot www example com quot      method   GET  scheme   https  authority   dnsserver example net  path    dns-query dns AAABAAABAAAAAAAAA3d3dwdleGFtcGxlA2NvbQAAAQAB accept   application dns-message  POST example   The same DNS query for  quot www example com quot   using the POST method would be     method   POST  scheme   https  authority   dnsserver example net  path    dns-query accept   application dns-message content-type   application dns-message content-length   33    lt 33 bytes represented by the following hex encoding gt  00 00 01 00 00 01 00 00  00 00 00 00 03 77 77 77 07 65 78 61 6d 70 6c 65  03 63 6f 6d 00 00 01 00 01  Other places to send DOH queries You can find a list of some public DNS resolvers that support DNS over HTTPS in a couple places   DNSCrypt has a long list of public DoH and DNSCrypt resolver on their Github  and a nice interactive version of the list at https   dnscrypt info public-servers  Wikipedia - comparison of public recursive nameservers List on Curl s wiki  short  list on dnsprivacy org  Of the above resources  I d say that the list on Curl s wiki and the DNSCrypt list are are probably the most complete and the most frequently updated  Curl s page also includes a list of open source tools for DoH  servers  proxies  client libs  etc

User · Answer

There is a javascript library DNS-JS com that does just this   DNS Query  dns-js com       DNS QueryType A      function data            console log data

User · Answer

Firefox has a built-in API for this since v60  for WebExtensions   https   developer mozilla org en-US docs Mozilla Add-ons WebExtensions API dns resolve

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Very late  but I guess many people will still land here through  Google Airlines   A moderm approach is to use WebRTC that doesn t require server support   https   hacking ventures local-ip-discovery-with-html5-webrtc-security-and-privacy-risk   Next code is a copy amp paste from http   net ipcalf com      NOTE  window RTCPeerConnection is  not a constructor  in FF22 23 var RTCPeerConnection     window RTCPeerConnection      window webkitRTCPeerConnection    window mozRTCPeerConnection   if  RTCPeerConnection   function          var rtc   new RTCPeerConnection  iceServers           if  window mozRTCPeerConnection            FF needs a channel stream to proceed         rtc createDataChannel      reliable false                  rtc onicecandidate   function  evt            if  evt candidate  grepSDP evt candidate candidate                rtc createOffer function  offerDesc            grepSDP offerDesc sdp           rtc setLocalDescription offerDesc          function  e    console warn  offer failed   e              var addrs   Object create null       addrs  0 0 0 0     false      function updateDisplay newAddr            if  newAddr in addrs  return          else addrs newAddr    true          var displayAddrs   Object keys addrs  filter function  k    return addrs k                document getElementById  list   textContent   displayAddrs join   or perhaps        n a                 function grepSDP sdp            var hosts                sdp split   r n   forEach function  line       c f  http   tools ietf org html rfc4566 page-39             if   line indexOf  a candidate             http   tools ietf org html rfc4566 section-5 13                 var parts   line split                 http   tools ietf org html rfc5245 section-15 1                     addr   parts 4                       type   parts 7                   if  type      host   updateDisplay addr                 else if   line indexOf  c                http   tools ietf org html rfc4566 section-5 7                 var parts   line split                            addr   parts 2                   updateDisplay addr                                                else       document getElementById  list   innerHTML     lt code gt ifconfig   grep inet   grep -v inet6   cut -d      -f2   tail -n1 lt  code gt        document getElementById  list   nextSibling textContent    In Chrome and Firefox your IP should display automatically  by the power of WebRTCskull

User · Answer

There s a third-party service which provides a CORS-friendly REST API to perform DNS lookups from the browser - https   exana io tools dns

User · Answer

If the client has Java installed  you could do something like this   ipAddress   java net InetAddress getLocalHost   getHostAddress      Other than that  you will probably have to use a server side script

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Edit  This question gave me an itch  so I put up a JSONP webservice on Google App Engine that returns the clients ip address  Usage    lt script type  application javascript  gt  function getip json     alert json ip      alerts the ip address    lt  script gt    lt script type  application javascript  src  http   jsonip appspot com  callback getip  gt   lt  script gt    Yay  no server proxies needed     Pure JS can t  If you have a server script under the same domain that prints it out you could send a XMLHttpRequest to read it

User · Answer

Doing this would require to break the browser sandbox  Try to let your server do the lookup and request that from the client side via XmlHttp

User · Answer

There s no notion of hosts or ip-addresses in the javascript standard library  So you ll have to access some external service to look up hostnames for you   I recommend hosting a cgi-bin which looks up the ip-address of a hostname and access that via javascript

User · Answer

As many people said you need to use an external service and call it  And that will only get you the DNS resolution from the server perspective   If that s good enough and if you just need DNS resolution you can use the following Docker container   https   github com kuralabs docker-webaiodns  Endpoints    GET   ipv6  domain    Perform a DNS resolution for given domain and return the associated IPv6  addresses            addresses               2a01 91ff  f03c 7e01 51bd fe1f               GET   ipv4  domain    Perform a DNS resolution for given domain and return the associated IPv4  addresses            addresses               139 180 232 162              My recommendation is that you setup your web server to reverse proxy to the container on a particular endpoint in your server serving your Javascript and call it using your standard Javascript Ajax functions

User · Answer

sure you can do that without using any addition  just pure javascript  by using this method of dns browser dns resolve  example com    but it is compatible just with FIREFOX 60 you can see more information on MDN https   developer mozilla org en-US docs Mozilla Add-ons WebExtensions API dns resolve

User · Answer

I don t think this is allowed by most browsers for security reasons  in a pure JavaScript context as the question asks

User · Answer

The hosted JSONP version works like a charm  but it seems it goes over its resources during night time most days  Eastern Time   so I had to create my own version   This is how I accomplished it with PHP    lt  php header  content-type  application json  charset utf-8      data   json encode   SERVER  REMOTE ADDR     echo   GET  callback            data           gt    Then the Javascript is exactly the same as before  just not an array    lt script type  application javascript  gt  function getip ip       alert  IP Address      ip      lt  script gt    lt script type  application javascript  src  http   www anotherdomain com file php callback getip  gt   lt  script gt    Simple as that   Side note  Be sure to clean your   GET if you re using this in any public-facing environment

[javascript] Can I perform a DNS lookup (hostname to IP address) using client-side Javascript?

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