diff --git a/Makefile.am b/Makefile.am
index 5f89871..ba541ce 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -105,6 +105,7 @@ SOURCES =									\
   guix-data-service/web/jobs/controller.scm					\
   guix-data-service/web/jobs/html.scm						\
   guix-data-service/web/nar/controller.scm					\
+  guix-data-service/web/nar/html.scm						\
   guix-data-service/web/query-parameters.scm					\
   guix-data-service/web/render.scm						\
   guix-data-service/web/repository/controller.scm				\
diff --git a/guix-data-service/web/nar/controller.scm b/guix-data-service/web/nar/controller.scm
index 755bdfb..53419e0 100644
--- a/guix-data-service/web/nar/controller.scm
+++ b/guix-data-service/web/nar/controller.scm
@@ -32,6 +32,7 @@
   #:use-module (guix base64)
   #:use-module (guix serialization)
   #:use-module (guix-data-service web render)
+  #:use-module (guix-data-service web nar html)
   #:use-module (guix-data-service model derivation)
   #:export (nar-controller
 
@@ -66,6 +67,9 @@
               ((key . value)
                (format #f "~a: ~a~%" key value)))
             %nix-cache-info))))
+    (('GET "substitutes")
+     (render-html
+      #:sxml (view-substitutes (%narinfo-signing-public-key))))
     (('GET "nar" derivation)
      (render-nar request
                  mime-types
diff --git a/guix-data-service/web/nar/html.scm b/guix-data-service/web/nar/html.scm
new file mode 100644
index 0000000..596d16b
--- /dev/null
+++ b/guix-data-service/web/nar/html.scm
@@ -0,0 +1,39 @@
+;;; Guix Data Service -- Information about Guix over time
+;;; Copyright © 2019 Christopher Baines <mail@cbaines.net>
+;;;
+;;; This program is free software: you can redistribute it and/or
+;;; modify it under the terms of the GNU Affero General Public License
+;;; as published by the Free Software Foundation, either version 3 of
+;;; the License, or (at your option) any later version.
+;;;
+;;; This program is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;; Affero General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU Affero General Public
+;;; License along with this program.  If not, see
+;;; <http://www.gnu.org/licenses/>.
+
+(define-module (guix-data-service web nar html)
+  #:use-module (ice-9 match)
+  #:use-module (gcrypt pk-crypto)
+  #:use-module (guix-data-service web view html)
+  #:export (view-substitutes))
+
+(define (view-substitutes narinfo-signing-public-key)
+  (layout
+   #:body
+   `(,(header)
+     (div
+      (@ (class "container"))
+      (div
+       (@ (class "row"))
+       (div
+        (@ (class "col-sm-12"))
+        (h1 "Substitutes")
+        ,@(if (canonical-sexp? narinfo-signing-public-key)
+              `((h3 "Public key")
+                (pre
+                 ,(canonical-sexp->string narinfo-signing-public-key)))
+              `((p "No signing key available.")))))))))