diff --git a/nix/configuration/roles/emacs/files/emacs/elisp/lang-d2.el b/nix/configuration/roles/emacs/files/emacs/elisp/lang-d2.el
new file mode 100644
index 0000000..a4b2696
--- /dev/null
+++ b/nix/configuration/roles/emacs/files/emacs/elisp/lang-d2.el
@@ -0,0 +1,16 @@
+(defun d2-format-buffer ()
+  "Run prettier."
+  (interactive)
+  (run-command-on-buffer "d2" "fmt" "-")
+  )
+
+(use-package d2-mode
+  :commands (d2-mode)
+  :hook (
+         (d2-mode . (lambda ()
+                      ;; (add-hook 'before-save-hook 'd2-format-buffer nil 'local)
+                      ))
+         )
+  )
+
+(provide 'lang-d2)
diff --git a/nix/configuration/roles/emacs/files/emacs/init.el b/nix/configuration/roles/emacs/files/emacs/init.el
index ad9ff8b..9a1bc6c 100644
--- a/nix/configuration/roles/emacs/files/emacs/init.el
+++ b/nix/configuration/roles/emacs/files/emacs/init.el
@@ -40,4 +40,6 @@
 
 (require 'lang-cmake)
 
+(require 'lang-d2)
+
 (load-directory autoload-directory)