Where is the documentation for WebApp.addHtmlAttributeHook

mattphet · August 5, 2026, 5:25pm

I cannot find documentation for #addHtmlAttributeHook anywhere, including at the WebApp documentation here: WebApp | Docs. Can anyone point me to the docs or can the docs be updated? Thanks!

fredmaiaarantes · August 5, 2026, 7:34pm

I think this isn’t formally documented, it’s only mentioned in passing in the SSR example on the WebApp docs page. The best reference is the source itself:

github.com

meteor/meteor/blob/devel/packages/webapp/webapp_server.js#L436


      
          * **returns**: <small>_Object_</small> `{ stop: function, callback: function }`
          * - `stop` <small>_Function_</small> Call `stop()` to stop getting callbacks.
          * - `callback` <small>_Function_</small> The passed in `callback`.
          * @locus Server
          * @param {addRuntimeConfigHookCallback} callback
          * See `addRuntimeConfigHookCallback` description.
          * @returns {Object} {{ stop: function, callback: function }}
          * Call the returned `stop()` to stop getting callbacks.
          * The passed in `callback` is returned also.
          */
          WebApp.addRuntimeConfigHook = function(callback) {
           return runtimeConfig.hooks.register(callback);
          };
          
          async function getBoilerplateAsync(request, arch, response) {
           let boilerplate = boilerplateByArch[arch];
           await runtimeConfig.hooks.forEachAsync(async hook => {
             const meteorRuntimeConfig = await hook({
               arch,
               request,
               encodedCurrentConfig: boilerplate.baseData.meteorRuntimeConfig,

WebApp.addHtmlAttributeHook(hook) registers a function that runs on every request. It receives a categorized request object and returns null or a plain object, and the returned attributes get applied to the <html> tag.

A common use is setting lang, which I did in a template I created a few years ago:

Meteor.startup(() => {
  WebApp.addHtmlAttributeHook(() => ({ lang: 'en' }));
});

github.com

fredmaiaarantes/meteorjs-template/blob/main/api/main.js

import { Meteor } from 'meteor/meteor';
import { Accounts } from 'meteor/accounts-base';
import { WebApp } from 'meteor/webapp';
import '/ui/App';

const appName = Meteor.settings?.public?.appInfo?.name || process.env.ROOT_URL;
Accounts.emailTemplates.siteName = appName;

Meteor.startup(() => {
  WebApp.addHtmlAttributeHook(() => ({ lang: 'en' }));
});

It’d be a nice small PR to the docs.