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Favicon emoji magic

5 December 2020

Favicons are fun.

They're a quirk in the otherwise dry list of rules which browsers obey. Every webpage is allowed to have a tiny picture associated with it, to be displayed alongside its title in tabs, bookmarks, shortcut icons, etc. They're similar to emoji - cute, bizarre bits of kitsch which have become ubiquitous across the internet.

I decided to bring those two ideas together for this website, and set an appropriate emoji as the favicon for each page. The index page should get a 👋, the blog should get a ✏️, the list of recent talks should get a 👄, etc.

Some technical context

I've built this website with jamstack principles in mind, using:

If you're interested, all of the code is on github.

Emoji as favicons

Favicons are typically set with <link> element in the page's <head>, pointing to one of the site's image assets:

  <link rel="icon" href="assets/favicon.png">

Although it's less common, the link's href argument can be supplied SVG data directly instead. Additionally, unicode characters can be read by SVG elements if they're appropriately wrapped.

Lea Verou demonstrated this trick on twitter a few months ago using the example below.

<svg xmlns="http://w3.org/2000/svg" viewBox="0 0 100 100">
  <text y=".9em" font-size="90">💩</text>

Bringing all of this together, I created a new Favicon component for my site which populates an SVG string with a supplied emoji, and adds it to the <head> of whichever page it's used on:

import Head from "next/head";

export default function Favicon({ emoji }) {
  const svg = `data:image/svg+xml,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100"><text y=".9em" font-size="90">${emoji}</text></svg>`;

  return (
      <link rel="icon" href={svg} />

I can now use the Favicon component in my website's default layout

(n.b. I've cut out the actual layout stuff here for clarity's sake)

import Favicon from "../components/favicon";

export default function DefaultLayout({
  faviconEmoji = "👋",
}) {
  return (
      <Favicon emoji={faviconEmoji} />

The default layout comes with a default favicon (👋), but this can now be set according to the page. For example, on the 404 page:

import BackButton from "../components/backButton";
import DefaultLayout from "../layouts/default";

export default function Custom404() {
  return (
    <DefaultLayout faviconEmoji="😬">
      <BackButton />
      <h1>404 - Page Not Found</h1>

Setting a unique emoji for every page

The content for this site is all written in prismic, and each page's content is fetched from the prismic API when the site is built. I don't manage the code for individual pages - they're all abstracted into a generic [uid].js file.

In principle, changing the favicon for each page should now be as simple as changing each page's title or description.

To get this working, I added a favicon field to the generic page structure in prismic, and pulled the corresponding field from the response in the [uid].js file. Here's what a blog post looks like in code:

const Post = ({ post }) => {
  const title = RichText.asText(post.data.title);
  const description = RichText.asText(post.data.standfirst);
  const date = formatDate(post.data.date);
  const emoji = RichText.asText(post.data.favicon);

  return (
    <DefaultLayout faviconEmoji={emoji}>
        <meta name="description" content={description} />
        <BackButton text="back to the blog" href="/blog" />
        <h1 className="py-0">{title}</h1>
        <div className="text-gray">{date}</div>
        <SliceZone sliceZone={post.data.body} />

Now, whenever I create a new page or blog post in prismic, I'm prompted to supply an emoji for the favicon

a prismic panel which shows a field where the favicon can be set

Setting the emoji favicon for this page in prismic

Those few extra lines of code handle the rest!