diff --git a/app/server/lib/sendAppPage.ts b/app/server/lib/sendAppPage.ts
index 991b39fb..f1a8bc10 100644
--- a/app/server/lib/sendAppPage.ts
+++ b/app/server/lib/sendAppPage.ts
@@ -116,6 +116,12 @@ export function makeSendAppPage(opts: {
   baseDomain?: string
 }) {
   const {server, staticDir, tag, testLogin} = opts;
+
+  // If env var GRIST_INCLUDE_CUSTOM_SCRIPT_URL is set, load it in a <script> tag on all app pages.
+  const customScriptUrl = process.env.GRIST_INCLUDE_CUSTOM_SCRIPT_URL;
+  const insertCustomScript: string = customScriptUrl ?
+    `<script src="${customScriptUrl}" crossorigin="anonymous"></script>` : '';
+
   return async (req: express.Request, resp: express.Response, options: ISendAppPageOptions) => {
     const config = makeGristConfig({
       homeUrl: !isSingleUserMode() ? server.getHomeUrl(req) : null,
@@ -153,6 +159,7 @@ export function makeSendAppPage(opts: {
       .replace("<!-- INSERT BASE -->", `<base href="${staticBaseUrl}">` + tagManagerSnippet)
       .replace("<!-- INSERT LOCALE -->", preloads)
       .replace("<!-- INSERT CUSTOM -->", customHeadHtmlSnippet)
+      .replace("<!-- INSERT CUSTOM SCRIPT -->", insertCustomScript)
       .replace(
         "<!-- INSERT CONFIG -->",
         `<script>window.gristConfig = ${jsesc(config, {isScriptContext: true, json: true})};</script>`
diff --git a/static/app.html b/static/app.html
index f87de801..fe174090 100644
--- a/static/app.html
+++ b/static/app.html
@@ -17,6 +17,7 @@
 <!-- INSERT LOCALE -->
 <!-- INSERT CONFIG -->
 <!-- INSERT CUSTOM -->
+<!-- INSERT CUSTOM SCRIPT -->
 
 <title><!-- INSERT TITLE --><!-- INSERT TITLE SUFFIX --></title>
 </head>
diff --git a/static/error.html b/static/error.html
index fe068f02..d1b8dff5 100644
--- a/static/error.html
+++ b/static/error.html
@@ -8,6 +8,7 @@
   <!-- INSERT LOCALE -->
   <!-- INSERT CONFIG -->
   <!-- INSERT CUSTOM -->
+  <!-- INSERT CUSTOM SCRIPT -->
   <title>Loading...<!-- INSERT TITLE SUFFIX --></title>
 </head>
 <body>
