Astro has quietly become the most interesting framework in the front-end ecosystem. Not because it does everything — it doesn’t — but because it makes very deliberate trade-offs: ship less JavaScript by default, use any UI framework you want, and treat content as a first-class concern.
Version 5 doubled down on all of this.
What changed in Astro 5
Content Layer
The most significant change is the unified Content Layer. Content collections are no longer limited to local files — you can now pull from any source using a loader. The built-in glob loader handles local markdown and MDX, but the API is open:
import { defineCollection, z } from 'astro:content';
import { glob } from 'astro/loaders';
export const collections = {
blog: defineCollection({
loader: glob({ pattern: '**/*.{md,mdx}', base: './src/content/blog' }),
schema: z.object({
title: z.string(),
pubDate: z.date(),
tags: z.array(z.string()).default([]),
}),
}),
};The content.config.ts file moves to src/content.config.ts (note: no content/ subdirectory). This trips people up on migration.
Server Islands
Astro 5 introduced Server Islands — components that opt into server rendering while the rest of the page stays static. This is different from full SSR: you get a static shell with selective hydration for dynamic parts.
---
import UserGreeting from '../components/UserGreeting.astro';
---
<UserGreeting server:defer>
<span slot="fallback">Loading...</span>
</UserGreeting>ViewTransitions → ClientRouter
The <ViewTransitions /> component was renamed to <ClientRouter />. The behaviour is the same — Astro handles page transitions using the View Transitions API with a JavaScript fallback.
import {ClientRouter} from 'astro:transitions';
<ClientRouter />Should you migrate?
If you’re on Astro 4, yes — but read the migration guide carefully. The content collection changes are the main friction point. If you have custom loaders or complex collection configs, budget a few hours.
If you’re starting fresh, start on 5. The DX is noticeably better.
What I’m building with it
This site is built on Astro 5 with a few opinionated choices:
- Static output only — no server components
- Tailwind CSS v4 via the
@tailwindcss/viteplugin (not@astrojs/tailwind) - Cloudflare Workers for deployment using the static assets approach
I’ll write more about each of these in future posts.