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astro

Can't load the middleware.

Astro

Astro Courses›

Astro Courses

Basics›

Components
Pages
Layouts
Project structure

Concepts›

Islands architecture
Why Astro?

Contribute›

Contribute to Astro

Develop And Build›

Develop and build

Editor Setup›

Editor setup

Getting Started›

Getting started

Guides›

Install And Setup›

Install Astro

Recipes›

Astro recipes
Installing a Vite or Rollup plugin
Analyze bundle size
Build a custom image component
Build HTML forms in Astro pages
Build forms with API routes
Use Bun with Astro
Call endpoints from the server
Verify a Captcha
Customize file names in the build output
Build your Astro site with Docker
Dynamically import images
Add icons to external links
Add i18n features
Create a dev toolbar app
Add last modified time
Add reading time
Add an RSS feed
Share state between Astro components
Share state between islands
Using streaming to improve page performance
Style rendered Markdown with Tailwind Typography

Reference›

Astro Adapter API
Astro render context
Template expressions reference
Astro Cache Provider API
CLI Commands
Configuration Reference
Astro Container API (experimental)
Astro Content Loader API
Dev Toolbar App API
Template directives reference
Error reference
Configuring experimental flags
Astro Font Provider API
Image Service API
Astro Integration API
Legacy flags
Astro Logger API
Programmatic Astro API (experimental)
Astro Renderer API
Routing Reference
Astro Session Driver API
Action called from the server without Astro.callAction().
Action not found.
An invalid Action query string was passed by a form.
Can't load the Astro actions.
Action handler returned invalid data.
An invalid Action query string was passed by a form.
Actions must be used with server output.
Adapter does not support server output.
Astro.glob() did not match any files.
Astro.glob() used outside of an Astro file.
Astro.response.headers must not be reassigned.
Cache is not enabled.
Cache provider not found.
Conflicting cache query configuration.
Cannot determine weight and style from font file.
Cannot extract the font type from the given URL.
Cannot fetch the given font file.
Cannot optimize SVG.
Astro can't render the route.
Cannot use the astro:config module without enabling the experimental feature.
Astro.clientAddress is not available in current adapter.
Collection does not exist
Legacy configuration detected.
Specified configuration file not found.
Content collection has an invalid type field.
Content collection is missing a loader definition.
Collection contains entries of a different type.
Content entry data does not match schema.
Content entry is missing an ID.
Content loader returned an entry with an invalid id.
Content schema should not contain slug.
Could not transform image.
CSP feature isn't enabled
CSS syntax error.
Data collection entry failed to parse.
Duplicate content entry slug.
The endpoint did not return a Response.
Invalid Environment Variable
Invalid environment variables.
envPrefix conflicts with secret environment variables.
Unsupported astro:env getSecret
Expected src to be an image.
Expected image options.
Expected image options, not an ESM-imported image.
Failed to retrieve remote image dimensions.
Astro couldn't find the correct page to render.
Could not import file.
Glob patterns are not supported in the file loader.
File parser not found.
Font family not found.
Font file URL not found.
Forbidden rewrite to a static route.
Failed to generate content types.
Invalid use of getDataEntryById or getEntryBySlug function.
getImage() must be used on the server.
Missing params property on getStaticPaths() route.
Invalid route parameter returned by getStaticPaths().
getStaticPaths RSS helper is not available anymore.
getStaticPaths() function required for dynamic routes.
The path doesn't contain any locale.
Internationalization routing is not enabled.
Image missing required "alt" property.
Image not found.
Cannot set both densities and widths.
Function incompatible with the current strategy.
Invalid component arguments.
Content entry data does not match schema.
Content entry frontmatter does not match schema.
Invalid content entry slug.
Invalid dynamic route.
Invalid frontmatter injection.
Invalid value returned by a route from getStaticPaths().
Invalid entry inside getStaticPaths()'s return value.
Invalid value returned by getStaticPaths().
Invalid glob pattern.
Invalid internationalization middleware configuration.
Error while loading image service.
Invalid prerender export.
Invalid redirect destination.
You attempted to rewrite a 404 inside a static page, and this isn't allowed.
Legacy content config file found.
Error in live content config.
Local images must be imported.
Value assigned to locals is not accepted.
Astro.locals is not serializable
locals must not be reassigned.
The configuration of the logger is not serializable.
Content collection frontmatter invalid.
Failed to parse Markdown frontmatter.
Image not found.
MDX integration missing.
Can't load the middleware.
The middleware didn't return a Response.
The middleware returned something that is not a Response object.
experimental_getFontFileURL() requires the request URL with on-demand rendering.
Missing image dimensions.
Index page not found.
The provided locale does not exist.
Missing value for client:media directive.
Enabled manual internationalization routing without having a middleware.
Could not find Sharp.
Content and data cannot be in same collection.
Cannot use server-side rendering without an adapter.
Cannot use server islands without an adapter.
No client entrypoint specified in renderer.
Missing hint on client:only directive.
Could not process image metadata.
No import found for component.
No matching renderer found.
No static path found for requested path.
Prerendered routes aren't supported when internationalization domains are enabled.
Invalid type returned by Astro page.
Page number param not found.
Astro.clientAddress cannot be used inside prerendered routes.
Prerendered dynamic endpoint has path collision.
Prerendered route generates the same path as another route.
A redirect must be given a location with the Location header.
Remote image is not allowed.
Attempted to render an undefined content collection entry.
Invalid slot name.
Unable to set response.
Astro couldn't find the route to rewrite, or if was found but it emitted an error during the rendering phase.
Cannot use Astro.rewrite() after the request body has been read.
Route not found.
Module is only available server-side.
Session storage was enabled but not configured.
Session flag not set
Session storage could not be initialized.
Session data could not be saved.
Sessions cannot be used with an adapter that doesn't support server output.
Astro.clientAddress is not available in prerendered pages.
Astro.redirect is not available in static mode.
Unable to load the logger.
Unavailable Astro global in getStaticPaths().
Unhandled rejection.
Unknown CLI error.
Unknown compiler error.
Unknown configuration error.
Unknown content collection error.
Unknown CSS error.
An unknown error occurred while reading or writing files to disk.
Unknown Markdown error.
Unknown Vite error.
Unsupported transform in content config.
Unsupported or malformed URL.
Unsupported image conversion.
Unsupported image format.
Experimental Chrome DevTools workspace
Experimental client prerendering
Experimental Intellisense for content collections
Experimental SVG optimization
Actions API Reference
Adapter Server Entrypoint API Reference
Image and Assets API Reference
Config imports API Reference
Content Collections API Reference
Environment Variables API Reference
Fetch routing API reference
Hono routing API reference
Internationalization API Reference
Middleware API Reference
Static Paths API Reference
View Transitions Router API Reference
Zod API Reference

Tutorial›

Build your first Astro Blog
Check in: Unit 1 - Setup
Check in: Unit 2 - Pages
Check in: Unit 3 - Components
Check in: Unit 4 - Layouts
Check in: Unit 5 - Astro API
Check in: Unit 6 - Astro Islands
About this Tutorial
Prepare your dev environment
Create your first Astro project
Write your first line of Astro
Store your repository online
Deploy your site to the web
Create your first Astro page
Write your first Markdown blog post
Add dynamic content about you
Style your About page
Add site-wide styling
Make a reusable Navigation component
Create a social media footer
Build it yourself - Header
Send your first script to the browser
Build your first layout
Create and pass data to a custom blog layout
Combine layouts to get the best of both worlds
Create a blog post archive
Generate tag pages
Build a tag index page
Add an RSS feed
Build your first Astro island
Back on dry land. Take your blog from day to night, no island required!
Congratulations!
Optional: Make a content collection

Upgrade Astro›

Upgrade Astro

llms.txt·full·src

Astro

Can't load the middleware.

Can't load the middleware.

throw new Error("Error thrown while loading the middleware.")

docharvest

Upstream documentation, vendored into versioned packs. Humans browse; agents fetch per-tech llms.txt.

/docs/github.com/docharvest site source

© 2026 · packs viaworkspaced· no site-wide /llms.txt