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#L232


      
            var combinedAttributes = {};
            (htmlAttributeHooks || []).forEach(function(hook) {
              var attributes = hook(request);
              if (attributes === null) return;
              if (typeof attributes !== 'object')
                throw Error('HTML attribute hook must return null or object');
              Object.assign(combinedAttributes, attributes);
            });
            return combinedAttributes;
          };
          WebApp.addHtmlAttributeHook = function(hook) {
            htmlAttributeHooks.push(hook);
          };
          
          // Serve app HTML for this URL?
          var appUrl = function(url) {
            if (url === '/favicon.ico' || url === '/robots.txt') return false;
          
            // NOTE: app.manifest is not a web standard like favicon.ico and
            // robots.txt. It is a file name we have chosen to use for HTML5
            // appcache URLs. It is included here to prevent using an appcache

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.

dupontbertrand · August 7, 2026, 8:32am

omw for the docs boss

harry97 · August 12, 2026, 11:06am

@dupontbertrand You beat me to it, lol

dupontbertrand · August 12, 2026, 4:24pm

Feel free to do it, I haven’t had time to do it yet

harry97 · August 12, 2026, 6:43pm

github.com/meteor/meteor

docs: document WebApp.addHtmlAttributeHook

meteor:devel ← harryadel:docs/webapp-html-attribute-hook

opened 06:32PM - 12 Aug 26 UTC

harryadel

+44 -11

## Summary - add generated API documentation for `WebApp.addHtmlAttributeHook` …- document its request object, return contract, merge behavior, and a `lang` example - correct the React SSR examples to call `WebAppInternals.disableBoilerplateResponse()` instead of emitting a `disableBoilerplateResponse` HTML attribute Forum context: https://forums.meteor.com/t/where-is-the-documentation-for-webapp-addhtmlattributehook/64729 ## Testing - `npm run docs:build` from `v3-docs/docs` ## Summary by CodeRabbit * **Documentation** * Added guidance for customizing `<html>` attributes during server-side rendering. * Documented callback behavior, request metadata, attribute precedence, and return requirements. * Updated React server-rendering examples to use the recommended boilerplate-response configuration method.