Can You Get A Users Local LAN IP Address Via JavaScript

Question

I know the initial reaction to this question is  quot no quot  and  quot it can t be done quot  and  quot you shouldn t need it  you are doing something wrong quot   What I m trying to do is get the users LAN IP address  and display it on the web page  Why  Because that s what the page I m working on is all about  showing as much information as possible about you  the visitor  https   www whatsmyip org more-info-about-you  So I m not actually DOING anything with the IP  other than showing it to the user for informational purposes  I used to do this by using a small Java applet  It worked pretty well  But these days  browser make you hit agree and trust so many times  to run even the most minor java applet  that I d rather not run one at all  So for a while I just got rid of this feature  but I d like it back if possible  It was something that I  as a computer consultant  would actually use from time to time  It s faster to go to this website to see what IP range a network is running on  than it is to go into System Preferences  Networking  and then whatever interface is active  So I m wondering  hoping  if there s some way to do it in javascript alone  Maybe some new object you can access  similar to the way javascript can ask the browser where is geographic location on earth is  Maybe theres something similar for client networking information  If not  perhaps theres some other way entirely to do it  The only ways I can think of are a java applet  or a flash object  I d rather not do either of those

User · Accepted Answer

As it turns out  the recent WebRTC extension of HTML5 allows javascript to query the local client IP address  A proof of concept is available here  http   net ipcalf com  This feature is apparently by design  and is not a bug  However  given its controversial nature  I would be cautious about relying on this behaviour  Nevertheless  I think it perfectly and appropriately addresses your intended purpose  revealing to the user what their browser is leaking

User · Answer

Chrome 76  Last year I used Linblow s answer  2018-Oct-19  to successfully discover my local IP via javascript  However  recent Chrome updates  76   have wonked this method so that it now returns an obfuscated IP  such as  1f4712db-ea17-4bcf-a596-105139dfd8bf local If you have full control over your browser  you can undo this behavior by turning it off in Chrome Flags  by typing this into your address bar  chrome   flags  and DISABLING the flag Anonymize local IPs exposed by WebRTC In my case  I require the IP for a TamperMonkey script to determine my present location and do different things based on my location  I also have full control over my own browser settings  no Corporate Policies  etc   So for me  changing the chrome   flags setting does the trick  Sources  https   groups google com forum   topic discuss-webrtc 6stQXi72BEU https   codelabs developers google com codelabs webrtc-web index html

User · Answer

x000D   x000D  function getUserIP onNewIP        onNewIp - your listener function for new IPs x000D      compatibility for firefox and chrome x000D    var myPeerConnection   window RTCPeerConnection    window mozRTCPeerConnection    window webkitRTCPeerConnection  x000D    var pc   new myPeerConnection   x000D        iceServers     x000D          x000D      noop   function       x000D      localIPs       x000D      ipRegex      0-9  1 3     0-9  1 3   3   a-f0-9  1 4    a-f0-9  1 4   7   g  x000D      key  x000D   x000D    function iterateIP ip    x000D      if   localIPs ip   onNewIP ip   x000D      localIPs ip    true  x000D      x000D    onNewIP x000D      create a bogus data channel x000D    pc createDataChannel      x000D   x000D       create offer and set local description x000D    pc createOffer   then function sdp    x000D      sdp sdp split   n   forEach function line    x000D        if  line indexOf  candidate    lt  0  return  x000D        line match ipRegex  forEach iterateIP   x000D          x000D   x000D      pc setLocalDescription sdp  noop  noop   x000D       catch function reason    x000D         An error occurred  so handle the failure to connect x000D        x000D   x000D      listen for candidate events x000D    pc onicecandidate   function ice    x000D      if   ice     ice candidate     ice candidate candidate     ice candidate candidate match ipRegex   return  x000D      ice candidate candidate match ipRegex  forEach iterateIP   x000D       x000D    x000D  getUserIP console log  x000D   x000D   x000D

User · Answer

The WebRTC API can be used to retrieve the client s local IP   However the browser may not support it  or the client may have disabled it for security reasons  In any case  one should not rely on this  hack  on the long term as it is likely to be patched in the future  see Cullen Fluffy Jennings s answer    The ECMAScript 6 code below demonstrates how to do that      ES6    const findLocalIp    logInfo   true    gt  new Promise   resolve  reject    gt        window RTCPeerConnection   window RTCPeerConnection                                 window mozRTCPeerConnection                                 window webkitRTCPeerConnection       if   typeof window RTCPeerConnection     undefined            return reject  WebRTC not supported by browser         let pc   new RTCPeerConnection        let ips            pc createDataChannel          pc createOffer         then offer   gt  pc setLocalDescription offer         catch err   gt  reject err        pc onicecandidate   event   gt            if    event     event candidate                    All ICE candidates have been sent              if   ips length    0                   return reject  WebRTC disabled or restricted by browser                 return resolve ips                      let parts   event candidate candidate split               let  base componentId protocol priority ip port  type    attr    parts          let component     rtp    rtpc             if     ips some e   gt  e    ip                ips push ip            if     logInfo               return           console log   candidate      base split      1            console log   component      component componentId - 1            console log    protocol      protocol           console log    priority      priority           console log          ip      ip           console log        port      port           console log        type      type            if   attr length                 console log  attributes                  for let i   0  i  lt  attr length  i    2                  console log   gt      attr i           attr i 1                       console log                  Notice I write return resolve     or return reject     as a shortcut  Both of those functions do not return anything   Then you may have something this     lt  DOCTYPE html gt   lt html lang  en  gt   lt head gt       lt meta charset  utf-8  gt       lt title gt Local IP lt  title gt   lt  head gt   lt body gt       lt h1 gt My local IP is lt  h1 gt       lt p id  ip  gt Loading   lt  p gt       lt script src  ip js  gt  lt  script gt       lt script gt      let p   document getElementById  ip        findLocalIp   then          ips   gt                let s                   ips forEach  ip   gt  s    ip     lt br gt                  p innerHTML   s                     err   gt  p innerHTML   err             lt  script gt   lt  body gt   lt  html gt

User · Answer

I cleaned up mido s post and then cleaned up the function that they found  This will either return false or an array  When testing remember that you need to collapse the array in the web developer console otherwise it s nonintuitive default behavior may deceive you in to thinking that it is returning an empty array   function ip local      var ip   false   window RTCPeerConnection   window RTCPeerConnection    window mozRTCPeerConnection    window webkitRTCPeerConnection    false    if  window RTCPeerConnection       ip         var pc   new RTCPeerConnection  iceServers       noop   function        pc createDataChannel        pc createOffer pc setLocalDescription bind pc   noop      pc onicecandidate   function event         if  event  amp  amp  event candidate  amp  amp  event candidate candidate           var s   event candidate candidate split   n        ip push s 0  split      4                  return ip      Additionally please keep in mind folks that this isn t something old-new like CSS border-radius though one of those bits that is outright not supported by IE11 and older  Always use object detection  test in reasonably older browsers  e g  Firefox 4  IE9  Opera 12 1  and make sure your newer scripts aren t breaking your newer bits of code  Additionally always detect standards compliant code first so if there is something with say a CSS prefix detect the standard non-prefixed code first and then fall back as in the long term support will eventually be standardized for the rest of it s existence

User · Answer

Now supported in internal-ip   An RTCPeerConnection can be used  In browsers like Chrome where a getUserMedia permission is required  we can just detect available input devices and request for them  const internalIp   async      gt        if   RTCPeerConnection            throw new Error  quot Not supported  quot              const peerConnection   new RTCPeerConnection   iceServers             peerConnection createDataChannel         peerConnection createOffer peerConnection setLocalDescription bind peerConnection        gt            peerConnection addEventListener  quot icecandidateerror quot    event    gt            throw new Error event errorText              return new Promise async resolve   gt            peerConnection addEventListener  quot icecandidate quot   async   candidate     gt                peerConnection close                            if  candidate  amp  amp  candidate candidate                    const result   candidate candidate split  quot   quot   4                  if  result endsWith  quot  local quot                          const inputDevices   await navigator mediaDevices enumerateDevices                       const inputDeviceTypes   inputDevices map    kind      gt  kind                       const constraints                           if  inputDeviceTypes includes  quot audioinput quot                              constraints audio   true                       else if  inputDeviceTypes includes  quot videoinput quot                              constraints video   true                       else                           throw new Error  quot An audio or video input device is required  quot                                              const mediaStream   await navigator mediaDevices getUserMedia constraints                      mediaStream getTracks   forEach track   gt  track stop                        resolve internalIp                                      resolve result

User · Answer

Update  This solution would not longer work because browsers are fixing webrtc leak  for more info on that read this other question  RTCIceCandidate no longer returning IP     In addition to afourney s answer this code works in browsers that support WebRTC  Chrome and Firefox   I heard there is a movement going on to implement a feature that makes sites request the IP  like in case of user s geo-location or user-media  though it has yet to be implemented in either of those browsers   Here is a modified version of the source code  reduced the lines  not making any stun requests since you only want Local IP not the Public IP   window RTCPeerConnection   window RTCPeerConnection    window mozRTCPeerConnection    window webkitRTCPeerConnection   compatibility for Firefox and chrome var pc   new RTCPeerConnection  iceServers       noop   function            pc createDataChannel       create a bogus data channel pc createOffer pc setLocalDescription bind pc   noop     create offer and set local description pc onicecandidate   function ice     if  ice  amp  amp  ice candidate  amp  amp  ice candidate candidate       var myIP      0-9  1 3     0-9  1 3   3   a-f0-9  1 4    a-f0-9  1 4   7    exec ice candidate candidate  1     console log  my IP     myIP        pc onicecandidate   noop          We are creating a dummy peer connection for the remote peer to contact us  We generally exchange ice candidates with each other and reading the ice candidates we can tell the ip of the user   You can find a demo at --  Demo

User · Answer

You can find more info about what limitations browsers will likely add to mitigate this and what IETF is doing about it as well as why this is needed at IETF SPEC on IP handling

[javascript] Can You Get A Users Local LAN IP Address Via JavaScript?

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