Astro now uses Vite 3, which comes with its own Migration Guide.
Components and JSX expressions in .md files is no longer supported by default. It can be enabled by setting the legacy.astroFlavoredMarkdown flag to true. In the future, we will be pushing users to our new @astrojs/mdx Integration for using components in Markdown.
‘@astrojs/image’ integration released!
Astro scoped styles now respect their authored specificity (see RFC0012). Please visually inspect your site after upgrading to confirm that styles are working as expected.
Astro.canonicalURL has been replaced by the new Astro.url helper.
The Markdown headers and getHeaders() utils have been renamed to headings and getHeadings().
The deprecated Markdown component has been removed from core and is now available as @astrojs/markdown-component.

Read the full migration guide for more details on upgrading your existing project.

New Features

astro dev HMR has been overhauled to provide more stable live reload behavior
astro dev error handling has been overhauled to provide a more seamless error handling experience
The new output configuration option builds to 'static' | 'server' targets
.html components and pages are now supported
.mdx components and pages are now supported via @astrojs/mdx
server output now supports custom 404 and 500 pages
server output now exposes Astro.clientAddress to get the current IP address per request

Patch Changes

#3988 9841c21e8 Thanks @Princesseuh! - Fix certain characters showing incorrectly in astro check
#4000 1c1b9da62 Thanks @tony-sull! - public assets should always take priority over page routes in SSR deployments
#4042 7e5ac1f45 Thanks @matthewp! - Ensure the before-hydration scripts are built
#3944 e82ff13f1 Thanks @mihkeleidast! - Add export keyword to astro config file stub created by add cli command
#3942 21462feb4 Thanks @AllanChain! - Use a base middleware for better base path handling in dev.
#3991 4dd341c8a Thanks @natemoo-re! - #3859 Overhaul Astro error handling, using Vite's built-in error overlay when possible
#4024 1215e731b Thanks @natemoo-re! - BREAKING Implement RFC0012 to preserve authored specificity for Astro scoped styles.

If you use a mix of global styles and Astro scoped styles, please visually inspect your site after upgrading to confirm that styles are working as expected.

If you previously relied on Astro's scoped styles to increase the specificity of your selectors, please update your selectors to use an additional class. For example, updating div to div.my-class will match the previous behavior.
#4046 c811be49a Thanks @matthewp! - Adds warnings for legacy markdown behavior
#4009 01ba07d8f Thanks @matthewp! - Fixes Lit compat with Vite 3.0.1
#4008 399d7e269 Thanks @bholmesdev! - Avoid parsing JSX, components, and Astro islands when using "plain" md mode. This brings markdown.mode: 'md' in-line with our docs description.
#4047 453c026aa Thanks @matthewp! - Perf: move getStaticPaths call during the build to during page generation
#3974 54865612e Thanks @Princesseuh! - Added missing media attributes from the JSX definitions for the meta element
#3932 27ee8b97a Thanks @natemoo-re! - Overhaul HMR handling for more stable live reload behavior
#4044 6f88597c3 Thanks @lostra01! - Added missing "loading" attribute to IFrameHTMLAttributes
#3995 b2b367c96 Thanks @bholmesdev! - Support YAML frontmatter in MDX files
#3976 fbef6a7f7 Thanks @natemoo-re! - Fix define:vars bugs with both style and script
#4023 4ca6a0933 Thanks @matthewp! - Fixes Node adapter to accept a request body
#4010 d503c5bf3 Thanks @matthewp! - Allow defining aliases with tsconfig
#4032 beddf073b Thanks @arimgibson! - Fix: find a hosting network differently based on Node version -- adjusted for Node v18.4+
#3867 7250e4e86 Thanks @natemoo-re! - Add support for .html components and pages
#3959 ddefb172f Thanks @FredKSchott! - Deprecate Astro.canonicalURL, in favor of Astro.url instead.
#3968 95eaa207d Thanks @bholmesdev! - Improve warning logs on astro.config change
#3959 ddefb172f Thanks @FredKSchott! - Add Astro.url helper for getting the request URL
#4031 6e27a5fdc Thanks @natemoo-re! - BREAKING Renamed Markdown utility function getHeaders() to getHeadings().
Updated dependencies [ba11b3399, 399d7e269, 00fab4ce1, 6e27a5fdc]:
- @astrojs/markdown-remark@0.13.0