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This is an older version of Eleventy. Full release history. Go to the newest Eleventy docs. You could try /docs/quicktips/not-found/ although it may not exist.

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Quick Tip #006—Adding a 404 Not Found Page to your Static Site

A 404: Not Found page is a pretty standard thing on the web. It’s particularly useful when someone shares a broken or mistyped link. You don’t need dynamic middleware to do this, it’s pretty easy to add to a statically generated site. There are a few options, depending on your web host:

But first let’s make our 404.html template:

---
title: Oops! Not Found
permalink: 404.html
---
<!doctype html>
<html lang="en">
    <head>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <title>{{ title }}</title>
    </head>
    <body>
        <h1>{{ title }}</h1>
        <p>This is where you should tell the user how to find their content. Maybe on the <a href="{{ "/" | url }}">home page?</a></p>
    </body>
</html>

Eleventy will output this template to 404.html.

If you’re using GitHub Pages or Netlify, there is no step two! A 404.html file in your output directory is all you need.

Netlify even has lovely multi-language 404 page support too using Redirects.

.htaccess #

For other hosts, if you use .htaccess for configuration you can use ErrorDocument. Make sure your root directory matches here!

ErrorDocument 404 /404.html

With --serve #

If you're using eleventy --serve, you can configure BrowserSync to do the 404 routing by passing a callback in your config. Read more on the BrowserSyncConfig option, the BrowserSync callbacks option, and how to provide a 404 using a BrowserSync callback.

Filename .eleventy.js
const fs = require("fs");

module.exports = function(eleventyConfig) {
  eleventyConfig.setBrowserSyncConfig({
    callbacks: {
      ready: function(err, bs) {
        const content_404 = fs.readFileSync('_site/404.html');

        bs.addMiddleware("*", (req, res) => {
          // Provides the 404 content without redirect.
          res.write(content_404);
          res.end();
        });
      }
    }
  });
};

Thank you Cassey Lottman.