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Check an IP(v4 or v6) against a subnet.

inSubnet (v0.0.8)

Install: npm install insubnet

This project is Unlicensed. In other words, I don't care what you do with it. However, if you make something interesting, I would like to check it out. I'm also accepting pull requests.

Build Status

Browser example at

IPv4 Address Notation Support:

  • Dotted decimal (
  • Dotted hexadecimal (0xC0.0x00.0x02.0xEB)
  • Dotted octal (0301.0250.0002.0353)
  • Hexadecimal (0xC00002EB)
  • Decimal (3221226219)
  • Octal (030000001353)


Examples in `./examples/` folder.

inSubnet.Auto(ip, subnet[, prefix length]) - Check to find out if <ip> is in <subnet>. Works with IPv4 and IPv6. Returns boolean.

     Examples: inSubnet.Auto('',''); // true
               inSubnet.Auto('','','16'); // true
               inSubnet.Auto('16909060',''); // true
               inSubnet.Auto('16909060','16908288/16'); // true
               inSubnet.Auto('2400:cb00::123','2400:cb00::/32'); // true
               inSubnet.Auto('','','16'); // false

inSubnet.IPv4(ip, subnet[, prefix length]) - Same as "Auto()" but for IPv4 only. - Returns boolean.

     Examples: See "Auto()" examples.

inSubnet.IPv4Dec(decimal, subnet[, prefix length]) - Same as "Auto()" but for IPv4 only. - Returns boolean.

     Examples: See "Auto()" examples.

inSubnet.IPv6(ip, subnet[, prefix length]) - Same as "Auto()" but for IPv6 only. - Returns boolean.

     Examples: inSubnet.IPv6('2400:cb00::123','2400:cb00::/32'); // true
               inSubnet.IPv6('2400:cb00::123','2400:cb00::','32'); // true
               inSubnet.IPv6('2500:cb00::123','2400:cb00::','32'); // false

inSubnet.isIP(string) - Check if <string> is an IP address. Works for IPv6 and IPv4. - Returns boolean.

     Examples: inSubnet.isIP(""); // true
               inSubnet.isIP("afd::1"); // true
               inSubnet.isIP("asd::1"); // false

inSubnet.isIPv4(string) - Same as "isIP()" but for IPv4 only. - Returns boolean.
     Examples: inSubnet.isIPv4(""); // true
               inSubnet.isIPv4(""); // false

inSubnet.isDecimal(string) - Same as "isIP()" but for IPv4 decimal notation only. - Returns boolean.
     Examples: inSubnet.isDecimal("16909060"); // true
               inSubnet.isDecimal("a16909060"); // false

inSubnet.isIPv6(string) - Same as "isIP()" but for IPv6 only. - Returns boolean.

     Examples: inSubnet.isIPv6("adf::1"); // true
               inSubnet.isIPv6("asf::1"); // false

inSubnet.Expand(ipv6[, zero]) - Expands an IPv6.
                                If <zero> is true, use single zeros. - Returns IPv6 or false.

     Examples: inSubnet.Expand("afd::1"); // 0afd:0000:0000:0000:0000:0000:0000:0001
               inSubnet.Expand("2001:4860:4860::8888"); // 2001:4860:4860:0000:0000:0000:0000:8888
               inSubnet.Expand("afd::1",true); // afd:0:0:0:0:0:0:1
               inSubnet.Expand("asd::1"); // false

inSubnet.Validate(ip[, subnets[, no update]]) - Check <ip> or an Array of IPs against an array of subnets set by "setSubnets()".
                                   If <subnets> is passed, uses "setSubnets()". If <no update> is true, do not call "setSubnets()".
                                   Returns boolean or an Array of boolean.

     Examples: inSubnet.Validate('',['','adf::1/32']);  // true
               inSubnet.Validate('2130706433'); // true - Uses previously set subnets.
               inSubnet.Validate(['','','adf::1']); // [true,false,true] - Uses previously set subnets.
               inSubnet.Validate(['','','adf::1'],['']); // [true,false,false] - Overwrite previously set subnets.

*inSubnet.Filter(array[, subnets[, no update]]) - Filter an Array of IP addresses against subnets set with "setSubnets()".
                                    If <subnets> is passed, uses "setSubnets()". If <no update> is true, do not call "setSubnets()".
                                    Returns IP or false, Array of valid IPs.

     Examples: inSubnet.Filter(['','adf::1',''],['','adf::1/32']); // ['','adf::1']
               inSubnet.Filter('',['','adf::1/32']); //
               inSubnet.Filter('adf::1',[''],true); // true - Uses previously set subnets.
               inSubnet.Filter('adf::1',['']); // false - Overwrite previously set subnets.
               inSubnet.Filter('',['','adf::1/32']); // false

*inSubnet.Clean(array[, filter[, sort]]) - Filter an array of IPs/subnets and return only valid IPs. Used in "setSubnets()".
                                          <filter> is the function to pass to "Array.filter()".
                                          <sort> is the function to pass to "Array.sort()" - Returns Object or false.
                                          NOTE: "Array.filter()" and "Array.sort()" are ran LAST after validating and expanding.

     Examples: inSubnet.Clean(['','']); // {ipv4:['',''],ipv6:[]}
               inSubnet.Clean(['','adf::1']); // {ipv4:[''],ipv6:['0adf:0000:0000:0000:0000:0000:0000:0001']}
               inSubnet.Clean(['adf::1','::1']); // {ipv4:[],ipv6:['0000:0000:0000:0000:0000:0000:0000:0001','0adf:0000:0000:0000:0000:0000:0000:0001']}
               inSubnet.Clean(['not an IP','subnet/23','asd::1']); // false

*inSubnet.setSubnets(subnets) - Set a list of subnets for "Validate()" and "Filter()".
                               WARNING: Overrides all previous "setSubnets()" calls. - Returns boolean.

     Examples: inSubnet.setSubnets(["","::1/32"]); // true
               inSubnet.setSubnets(["not","subnets","subnet/32"]); // false

*Only supports IPv4 dotted decimal notation and IPv6.


  • Figure out what should be in the TODO and then write it! (Done!?)
  • Write a better README! (Is this happening?)
  • Write a simple HTTP example for CloudFlare. (Look in ./examples/cloudflare.js)
  • Make "Exporter" better.

Functionality Requests:

  • *Add support for IPv6 dotted notation. (::

  • Add support for more IPv4 notations. See "IPv4 Address Notation Support" above.

    *I probably wont get to this any time soon... Sorry for those who need/want it. Please feel free to submit a pull request.