Officially support redirecting to an external URL

[flavianh]

Summary

At the moment, using

export default defineConfig({
  ...
  redirects: {
    '/test2': {
      status: 302,
      destination: 'https://mysecondsite.com/test2',
    },
  },
});

redirects to https://myfirstsite.com/https://mysecondsite.com/test2, when it should redirect to the external URL directly.

This is something the Vercel CLI correctly warns about: [WARN] [redirects] Redirecting to an external URL is not officially supported.

Background & Motivation

This is particularly useful to preserve links when migrating URLs into another domain or subdomain.

Goals

My own case was:

1. Initially, I had a Ghost blog hosted on mysite.com
2. I moved it to blog.mysite.com, and mysite.com now hosts an Astro website. Links such as mysite.com/article1 must redirect to blog.mysite.com/article1.

It is possible to use redirect lists in Cloudflare but this costs too much if the list of URLs is too large.
Redirecting with Astro allows to maintain this list more easily (as it can be contained in a plain text file such as a JSON or JS file).

[TheMikeyRoss]

Is this now possible?

[gxjansen]

On the current latest Astro 4.14.2 you'll still see the CLI warning and the redirect doesn't work (it'll return a 404)

[marty0678]

I'm using Astro 4.15.1 and I get the warning but it does appear to work and redirect to the other domain.

[mihailthebuilder]

I've been using this for a few weeks (on 4.15.9) and it works fine. Only just noticed the warning in my CLI ^_^

[ematipico]

Be all aware that you're leveraging a possible bug in Astro. This means that external redirects aren't officially supported and this could break your website.

[marcomonsanto]

Not using config redirects, but I was able to use Response.redirect('URL') inside the middleware to point to an external URL, could be an option if you can use middleware.

[JanTrichter]

I had a similar issue that I needed to go from my site's /admin to an external web page.

I solved it for now by adding an admin.astro file in the /pages directory and then redirect to the new website using JavaScript like this:

/pages/admin.astro

<script>
    window.location.href = "https://website.com/whatever";
</script>

[ematipico]

I have a draft PR ready: withastro/astro#12979

[ematipico]

Astro v5.2 ships with the support of external redirects! https://astro.build/blog/astro-520/