diff --git a/pkgs/default.nix b/pkgs/default.nix
index 58f004a..164c0b3 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -4,6 +4,8 @@ rec {
 
   havm = pkgs.callPackage ./havm { };
 
+  i3-get-window-criteria = pkgs.callPackage ./i3-get-window-criteria { };
+
   lohr = pkgs.callPackage ./lohr { };
 
   nolimips = pkgs.callPackage ./nolimips { };
diff --git a/pkgs/i3-get-window-criteria/default.nix b/pkgs/i3-get-window-criteria/default.nix
new file mode 100644
index 0000000..185e1e4
--- /dev/null
+++ b/pkgs/i3-get-window-criteria/default.nix
@@ -0,0 +1,43 @@
+{ coreutils, gnused, makeWrapper, lib, shellcheck, stdenvNoCC, xorg }:
+stdenvNoCC.mkDerivation rec {
+  pname = "i3-get-window-criteria";
+  version = "0.1.0";
+
+  src = ./i3-get-window-criteria;
+
+  phases = [ "buildPhase" "installPhase" "fixupPhase" ];
+
+  buildInputs = [
+    makeWrapper
+    shellcheck
+  ];
+
+  buildPhase = ''
+    shellcheck $src
+  '';
+
+  installPhase = ''
+    mkdir -p $out/bin
+    cp $src $out/bin/${pname}
+    chmod a+x $out/bin/${pname}
+  '';
+
+  wrapperPath = lib.makeBinPath [
+    coreutils
+    gnused
+    xorg.xprop
+    xorg.xwininfo
+  ];
+
+  fixupPhase = ''
+    patchShebangs $out/bin/${pname}
+    wrapProgram $out/bin/${pname} --prefix PATH : "${wrapperPath}"
+  '';
+
+  meta = with lib; {
+    description = "Helper script to query i3 window criterions";
+    homepage = "https://gitea.belanyi.fr/ambroisie/nix-config";
+    license = with licenses; [ mit ];
+    platforms = platforms.unix;
+  };
+}
diff --git a/pkgs/i3-get-window-criteria/i3-get-window-criteria b/pkgs/i3-get-window-criteria/i3-get-window-criteria
new file mode 100755
index 0000000..e68641c
--- /dev/null
+++ b/pkgs/i3-get-window-criteria/i3-get-window-criteria
@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+
+# i3-get-window-criteria - Get criteria for use with i3 config commands
+
+# To use, run this script, then click on a window.
+# Output is in the format: [<name>=<value> <name>=<value> ...]
+
+# Known problem: when WM_NAME is used as fallback for the 'title="<string>"' criterion,
+# quotes in "<string>" are not escaped properly. This is a problem with the output of `xprop`,
+# reported upstream: https://bugs.freedesktop.org/show_bug.cgi?id=66807
+
+match_int='[0-9][0-9]*'
+match_string='".*"'
+match_qstring='"[^"\\]*(\\.[^"\\]*)*"' # NOTE: Adds 1 backreference
+
+{
+    # Run xwininfo, get window id
+    window_id=$(xwininfo -int | sed -nre "s/^xwininfo: Window id: ($match_int) .*$/\1/p")
+    echo "id=$window_id"
+
+    # Run xprop, transform its output into i3 criteria. Handle fallback to
+    # WM_NAME when _NET_WM_NAME isn't set
+    xprop -id "$window_id" |
+        sed -nr \
+            -e "s/^WM_CLASS\(STRING\) = ($match_qstring), ($match_qstring)$/instance=\1\nclass=\3/p" \
+            -e "s/^WM_WINDOW_ROLE\(STRING\) = ($match_qstring)$/window_role=\1/p" \
+            -e "/^WM_NAME\(STRING\) = ($match_string)$/ {s//title=\1/; h}" \
+            -e "/^_NET_WM_NAME\(UTF8_STRING\) = ($match_qstring)$/ {s//title=\1/; h}" \
+            -e '$ {g; p}'
+} | sort | tr "\n" " " | sed -r 's/^(.*) $/[\1]\n/'