diff --git a/README.md b/README.md
index 81abc4c..790b280 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,23 @@ nix build .#nixosConfigurations.parsons.config.system.build.toplevel
 
 (but you might have trouble deploying it)
 
+## Working on websites
+
+Websites are exposed as flake outputs: if you're working on a website & want to
+check it in a browser, do e.g.
+
+~~~shell
+nix run .#\"muc.hacc.earth\"
+~~~
+
+to start a local http server (note that some of our websites need a directory
+to be built in; these use `/tmp/hacc-website`).
+
+To add a new website, add a new subdirectory to `websites`; nix will generate a
+vhost config based on that directory's name. Add a `default.nix` in your directory
+describing how to build the website, and give its derivation a `watch` attribute
+to make the `nix run` setup work.
+
 ## I don't want to build this long dependency / want a cached version!
 
 If it's still available on parsons from a previous deploy, do:
diff --git a/flake.nix b/flake.nix
index 46ab7e2..86d01e9 100644
--- a/flake.nix
+++ b/flake.nix
@@ -85,6 +85,9 @@
       checks = builtins.mapAttrs
         (system: deployLib: deployLib.deployChecks self.deploy)
         deploy-rs.lib;
+
+      packages.x86_64-linux =
+        self.nixosConfigurations.parsons.config.hacc.websites.builders;
     };
 
 }
diff --git a/modules/websites.nix b/modules/websites.nix
index 0227dcb..0b701cb 100644
--- a/modules/websites.nix
+++ b/modules/websites.nix
@@ -21,33 +21,42 @@ in
       default = [];
       description = "subdirectories that shouldn't be published";
     };
+    builders = mkOption {
+      type = types.lazyAttrsOf types.package;
+      default = {};
+      description = "exposes website builders, for use with nix run";
+    };
   };
 
-  config = mkIf cfg.enable {
+  config = let
+    subdirs =
+      let dirAttrs = filterAttrs
+        (n: v: v == "directory" || lists.elem n cfg.ignore)
+        (builtins.readDir cfg.directory);
+      in mapAttrsToList (n: v: n) dirAttrs;
+    mkWebsiteDrv = subdir:
+      pkgs.callPackage "${cfg.directory}/${subdir}" {};
+    mkWebsiteVHost = subdir: {
+      name = subdir;
+      # the nginx virtualhost config (for all sites) goes in here
+      value = {
+        enableACME = true;
+        forceSSL = true;
+
+        locations."/".root =
+          (mkWebsiteDrv subdir).outPath;
+      };
+    };
+  in mkIf cfg.enable {
     services.nginx = {
       enable = true;
       virtualHosts =
-        let
-          subdirs =
-            let dirAttrs = filterAttrs
-              (n: v: v == "directory" || lists.elem n cfg.ignore)
-              (builtins.readDir cfg.directory);
-            in mapAttrsToList (n: v: n) dirAttrs;
-
-          mkWebsite = subdir: {
-            name = subdir;
-            # the nginx virtualhost config (for all sites) goes in here
-            value = {
-              enableACME = true;
-              forceSSL = true;
-
-              # naive string interpolation is safe here since nix will always immediately
-              # resolve relative paths to absolute paths; it's not lazy about that.
-              locations."/".root =
-                (pkgs.callPackage "${cfg.directory}/${subdir}" {}).outPath;
-            };
-          };
-        in listToAttrs (map mkWebsite subdirs);
+        listToAttrs (map mkWebsiteVHost subdirs);
     };
+    hacc.websites.builders =
+      listToAttrs (map (subdir: {
+        name = subdir;
+        value = if (mkWebsiteDrv subdir) ? watch then (mkWebsiteDrv subdir).watch else null;
+      }) subdirs);
   };
 }
diff --git a/websites/hacc.earth/default.nix b/websites/hacc.earth/default.nix
index 3b7d2d3..eb80f4e 100644
--- a/websites/hacc.earth/default.nix
+++ b/websites/hacc.earth/default.nix
@@ -1,6 +1,6 @@
-{ stdenvNoCC }:
+{ stdenvNoCC, sfz, writeScriptBin }:
 
-stdenvNoCC.mkDerivation {
+stdenvNoCC.mkDerivation rec {
   name = "hacc.earth-static";
 
   src = ./.;
@@ -13,4 +13,7 @@ stdenvNoCC.mkDerivation {
     rm $out/default.nix
   '';
 
+  watch = writeScriptBin "watch" ''
+    ${sfz}/bin/sfz -r ${src} "$@"
+  '';
 }
diff --git a/websites/help.studentsforfuture.info/default.nix b/websites/help.studentsforfuture.info/default.nix
index 501be08..069a6cb 100644
--- a/websites/help.studentsforfuture.info/default.nix
+++ b/websites/help.studentsforfuture.info/default.nix
@@ -1,6 +1,6 @@
-{ stdenvNoCC }:
+{ stdenvNoCC, sfz, writeScriptBin }:
 
-stdenvNoCC.mkDerivation {
+stdenvNoCC.mkDerivation rec {
   name = "muc.hacc.earth-static";
 
   src = ./.;
@@ -13,4 +13,7 @@ stdenvNoCC.mkDerivation {
     rm $out/default.nix
   '';
 
+  watch = writeScriptBin "watch" ''
+    ${sfz}/bin/sfz -r ${src}
+  '';
 }
diff --git a/websites/infra4future.de/default.nix b/websites/infra4future.de/default.nix
index b67444f..72d86f7 100644
--- a/websites/infra4future.de/default.nix
+++ b/websites/infra4future.de/default.nix
@@ -1,6 +1,6 @@
-{ jekyll, stdenvNoCC }:
+{ jekyll, stdenvNoCC, writeScriptBin }:
 
-stdenvNoCC.mkDerivation {
+stdenvNoCC.mkDerivation rec {
   name = "infra4future.de-static";
 
   src = ./.;
@@ -11,4 +11,8 @@ stdenvNoCC.mkDerivation {
     ${jekyll}/bin/jekyll build -d $out --disable-disk-cache
   '';
 
+  watch = writeScriptBin "watch" ''
+    rm -rf /tmp/hacc-website
+    ${jekyll}/bin/jekyll serve -s ${src} --disable-disk-cache -d /tmp/hacc-website
+  '';
 }
diff --git a/websites/muc.hacc.earth/default.nix b/websites/muc.hacc.earth/default.nix
index 501be08..069a6cb 100644
--- a/websites/muc.hacc.earth/default.nix
+++ b/websites/muc.hacc.earth/default.nix
@@ -1,6 +1,6 @@
-{ stdenvNoCC }:
+{ stdenvNoCC, sfz, writeScriptBin }:
 
-stdenvNoCC.mkDerivation {
+stdenvNoCC.mkDerivation rec {
   name = "muc.hacc.earth-static";
 
   src = ./.;
@@ -13,4 +13,7 @@ stdenvNoCC.mkDerivation {
     rm $out/default.nix
   '';
 
+  watch = writeScriptBin "watch" ''
+    ${sfz}/bin/sfz -r ${src}
+  '';
 }
diff --git a/websites/mumble.infra4future.de/default.nix b/websites/mumble.infra4future.de/default.nix
index 27b5234..615f53b 100644
--- a/websites/mumble.infra4future.de/default.nix
+++ b/websites/mumble.infra4future.de/default.nix
@@ -1,6 +1,6 @@
-{ jekyll, stdenvNoCC }:
+{ jekyll, stdenvNoCC, writeScriptBin }:
 
-stdenvNoCC.mkDerivation {
+stdenvNoCC.mkDerivation rec {
   name = "mumble.infra4future.de-static";
 
   src = ./.;
@@ -11,4 +11,8 @@ stdenvNoCC.mkDerivation {
     ${jekyll}/bin/jekyll build -d $out --disable-disk-cache
   '';
 
+  watch = writeScriptBin "watch" ''
+    rm -rf /tmp/hacc-website
+    ${jekyll}/bin/jekyll serve -s ${src} --disable-disk-cache -d /tmp/hacc-website
+  '';
 }