diff --git a/lib/philomena_query/ip_mask.ex b/lib/philomena_query/ip_mask.ex
new file mode 100644
index 00000000..6bf7c192
--- /dev/null
+++ b/lib/philomena_query/ip_mask.ex
@@ -0,0 +1,109 @@
+defmodule PhilomenaQuery.IpMask do
+  @moduledoc """
+  Postgres IP masks.
+  """
+
+  @doc """
+  Parse a netmask from a string parameter, producing an `m:Postgrex.INET` type suitable for use in
+  a containment (<<=, <<, >>, >>=) query. Ignores invalid strings and passes the IP through on
+  error. [Postgres documentation](https://www.postgresql.org/docs/current/functions-net.html)
+  has more information on `inet` operations.
+
+  > #### Info {: .info}
+  >
+  > Netmasks lower than /8 are clamped to a minimum of /8. Such low masks are unlikely to be
+  > useful and this avoids producing very expensive masks to evaluate.
+
+  ## Examples
+
+      iex> parse_mask(%Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}, %{"mask" => "12"})
+      %Postgrex.INET{address: {192, 160, 0, 0}, netmask: 12}
+
+      iex> parse_mask(%Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}, %{"mask" => "4"})
+      %Postgrex.INET{address: {192, 0, 0, 0}, netmask: 8}
+
+      iex> parse_mask(%Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}, %{"mask" => "64"})
+      %Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}
+
+      iex> parse_mask(%Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}, %{"mask" => "e"})
+      %Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}
+
+      iex> parse_mask(%Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}, %{})
+      %Postgrex.INET{address: {192, 168, 1, 1}, netmask: 32}
+
+      iex> parse_mask(%Postgrex.INET{
+      ...>  address: {0x2001, 0xab0, 0x33a8, 0xd6e2, 0x10e9, 0xac1b, 0x9b0f, 0x67bc},
+      ...>  netmask: 128
+      ...> }, %{"mask" => "64"})
+      %Postgrex.INET{address: {8193, 2736, 13224, 55010, 0, 0, 0, 0}, netmask: 64}
+
+  """
+  @spec parse_mask(Postgrex.INET.t(), map()) :: Postgrex.INET.t()
+  def parse_mask(ip, params)
+
+  def parse_mask(ip, %{"mask" => mask}) when is_binary(mask) do
+    case Integer.parse(mask) do
+      {mask, _rest} ->
+        mask = clamp_mask(ip.address, mask)
+        address = apply_mask(ip.address, mask)
+
+        %Postgrex.INET{address: address, netmask: mask}
+
+      _ ->
+        ip
+    end
+  end
+
+  def parse_mask(ip, _params), do: ip
+
+  defp clamp(n, min, _max) when n < min, do: min
+  defp clamp(n, _min, max) when n > max, do: max
+  defp clamp(n, _min, _max), do: n
+
+  defp clamp_mask(ip, mask) do
+    # Clamp mask length:
+    # - low end 8 (too taxing to evaluate)
+    # - high end address_bits (limit of address)
+    case tuple_size(ip) do
+      4 ->
+        clamp(mask, 8, 32)
+
+      8 ->
+        clamp(mask, 8, 128)
+    end
+  end
+
+  defp unit_length(ip) when tuple_size(ip) == 4, do: 8
+  defp unit_length(ip) when tuple_size(ip) == 8, do: 16
+
+  defp apply_mask(ip, mask) when is_tuple(ip) do
+    # Determine whether elements are octets or hexadectets
+    length = unit_length(ip)
+
+    # 1. Convert tuple to list of octets/hexadectets
+    # 2. Convert list to bitstring
+    # 3. Perform truncation operation on bitstring
+    # 4. Convert bitstring back to list of octets/hexadectets
+    # 5. Convert list to tuple
+
+    ip
+    |> Tuple.to_list()
+    |> list_to_bits(length)
+    |> apply_mask(mask)
+    |> bits_to_list(length)
+    |> List.to_tuple()
+  end
+
+  defp apply_mask(ip, mask) when is_binary(ip) do
+    # Truncate bit size of ip to mask length and zero-fill the remainder
+    <<ip::bits-size(mask), 0::integer-size(bit_size(ip)-mask)>>
+  end
+
+  defp list_to_bits(list, unit_length) do
+    for u <- list, into: <<>>, do: <<u::integer-size(unit_length)>>
+  end
+
+  defp bits_to_list(bits, unit_length) do
+    for <<u::integer-size(unit_length) <- bits>>, do: u
+  end
+end
diff --git a/lib/philomena_web/controllers/ip_profile/source_change_controller.ex b/lib/philomena_web/controllers/ip_profile/source_change_controller.ex
index f5bf868c..d82359e2 100644
--- a/lib/philomena_web/controllers/ip_profile/source_change_controller.ex
+++ b/lib/philomena_web/controllers/ip_profile/source_change_controller.ex
@@ -1,25 +1,27 @@
 defmodule PhilomenaWeb.IpProfile.SourceChangeController do
   use PhilomenaWeb, :controller
 
+  alias PhilomenaQuery.IpMask
   alias Philomena.SourceChanges.SourceChange
   alias Philomena.Repo
   import Ecto.Query
 
   plug :verify_authorized
 
-  def index(conn, %{"ip_profile_id" => ip}) do
+  def index(conn, %{"ip_profile_id" => ip} = params) do
     {:ok, ip} = EctoNetwork.INET.cast(ip)
+    range = IpMask.parse_mask(ip, params)
 
     source_changes =
       SourceChange
-      |> where(ip: ^ip)
+      |> where(fragment("? >>= ip", ^range))
       |> order_by(desc: :id)
       |> preload([:user, image: [:user, :sources, tags: :aliases]])
       |> Repo.paginate(conn.assigns.scrivener)
 
     render(conn, "index.html",
       title: "Source Changes for IP `#{ip}'",
-      ip: ip,
+      ip: range,
       source_changes: source_changes
     )
   end
diff --git a/lib/philomena_web/controllers/ip_profile/tag_change_controller.ex b/lib/philomena_web/controllers/ip_profile/tag_change_controller.ex
index b9779913..bdfebc29 100644
--- a/lib/philomena_web/controllers/ip_profile/tag_change_controller.ex
+++ b/lib/philomena_web/controllers/ip_profile/tag_change_controller.ex
@@ -1,6 +1,7 @@
 defmodule PhilomenaWeb.IpProfile.TagChangeController do
   use PhilomenaWeb, :controller
 
+  alias PhilomenaQuery.IpMask
   alias Philomena.TagChanges.TagChange
   alias Philomena.Repo
   import Ecto.Query
@@ -9,10 +10,11 @@ defmodule PhilomenaWeb.IpProfile.TagChangeController do
 
   def index(conn, %{"ip_profile_id" => ip} = params) do
     {:ok, ip} = EctoNetwork.INET.cast(ip)
+    range = IpMask.parse_mask(ip, params)
 
     tag_changes =
       TagChange
-      |> where(ip: ^ip)
+      |> where(fragment("? >>= ip", ^range))
       |> added_filter(params)
       |> preload([:tag, :user, image: [:user, :sources, tags: :aliases]])
       |> order_by(desc: :id)
@@ -20,7 +22,7 @@ defmodule PhilomenaWeb.IpProfile.TagChangeController do
 
     render(conn, "index.html",
       title: "Tag Changes for IP `#{ip}'",
-      ip: ip,
+      ip: range,
       tag_changes: tag_changes
     )
   end
diff --git a/lib/philomena_web/templates/ip_profile/show.html.slime b/lib/philomena_web/templates/ip_profile/show.html.slime
index eb3ac25c..da8acd3d 100644
--- a/lib/philomena_web/templates/ip_profile/show.html.slime
+++ b/lib/philomena_web/templates/ip_profile/show.html.slime
@@ -11,8 +11,17 @@ ul
 
 h2 Administration Options
 ul
-  li = link "View tag changes", to: ~p"/ip_profiles/#{to_string(@ip)}/tag_changes"
-  li = link "View source URL history", to: ~p"/ip_profiles/#{to_string(@ip)}/source_changes"
+  li
+    => link "View tag changes", to: ~p"/ip_profiles/#{to_string(@ip)}/tag_changes"
+    = if ipv6?(@ip) do
+      ' &hellip;
+      = link "(/64)", to: ~p"/ip_profiles/#{to_string(@ip)}/tag_changes?mask=64"
+  li
+    => link "View source URL history", to: ~p"/ip_profiles/#{to_string(@ip)}/source_changes"
+    = if ipv6?(@ip) do
+      ' &hellip;
+      = link "(/64)", to: ~p"/ip_profiles/#{to_string(@ip)}/source_changes?mask=64"
+
   li = link "View reports this IP has made", to: ~p"/admin/reports?#{[rq: "ip:#{@ip}"]}"
   li = link "View IP ban history", to: ~p"/admin/subnet_bans?#{[ip: to_string(@ip)]}"
   li = link "Ban this sucker", to: ~p"/admin/subnet_bans/new?#{[specification: to_string(@ip)]}"
diff --git a/lib/philomena_web/views/ip_profile_view.ex b/lib/philomena_web/views/ip_profile_view.ex
index 9aef6c29..a9f99f20 100644
--- a/lib/philomena_web/views/ip_profile_view.ex
+++ b/lib/philomena_web/views/ip_profile_view.ex
@@ -1,3 +1,8 @@
 defmodule PhilomenaWeb.IpProfileView do
   use PhilomenaWeb, :view
+
+  @spec ipv6?(Postgrex.INET.t()) :: boolean()
+  def ipv6?(ip) do
+    tuple_size(ip.address) == 8
+  end
 end