Changesets

You will be responsible for writing a changeset for your Astro PR. This is a Markdown file that states:

• which repository has changed
• the kind of change according to Astro’s semantic versioning
• a message describing the change that will be publicly displayed on the repo’s CHANGELOG

my-super-cool-changeset.md

---
'astro': patch
---
Fixes unexpected `undefined` value when calling an action from the client without a return value

Format

Begin your changeset message with a present tense verb that completes a sentence in the style of: “This PR …” or “This contribution …”

• Adds
• Removes
• Fixes
• Updates
• Refactors
• Improves
• Deprecates

Finish the introductory sentence with a message focusing on what has changed that is meaningful to a user of Astro. It is usually more helpful to describe the change as someone building an Astro site will experience it, instead of describing how you fixed it.

You may then include additional paragraphs if necessary to describe the change in more detail. This may not be needed for a small bug fix, but is often helpful if the reader must make a change to their own code, or needs to understand how the change might affect them.

The level of detail of a changeset depends on the type of change (e.g. patch vs minor, breaking or not, only affects integration authors etc.) You may also use <h4> - <h6> Markdown headings to break your longer content into sections.

Don’t hide the good stuff in the changeset!

CHANGELOGS are often read only once, when someone is updating to the latest version of a package. Documentation is a constant reference that will be revisited and consulted frequently.

Make sure that the helpful explanations and examples for your fellow developers in both your changeset and your PR description are captured in the actual feature documentation, too!

Patch updates

These updates are often fixes, refactors or other small improvements. They are typically not user-facing, and do not require someone to update their own project code.

Verbs like “fixes” and “refactors” are helpful to let readers know this is an internal or implementation change that they do not need to worry about. At the same time, these messages are helpful to someone who is interested in keeping up with small changes to the codebase.

Often one line is enough to describe your change meaningfully to an Astro user:

my-patch-changeset.md

---
'astro': patch
---
Fixes a bug where the toolbar audit would incorrectly flag images as above the fold

my-patch-changeset.md

---
'astro': patch
---
Refactors internal handling of styles and scripts for content collections to improve build performance

my-patch-changeset.md

---
'astro': patch
---
Updates the `HTMLAttributes` type exported from `astro` to allow data attributes

These do not need to be full sentences and do not need end punctuation unless you write multiple sentences.

Help your reader figure out if this is change important to them

Even though these are small changes described by very short sentences, they still need to communicate a lot!

Check that you have clearly stated not just what has changed but also who needs to know. If your reader can identify that a change is important to them, they can always seek out further information if they need to know more.

Tips and Examples

For a great changeset message:

Include the specific API changed (using inline code highlighting as appropriate) when your change might not be easy to identify so that your reader can easily tell whether it’s something they are using and need to care about:

Improves automatic fallbacks generation

vs

✅ Improves automatic fallbacks generation for the experimental Fonts API

When the specific API change is not user-facing (e.g. a type not publicly exposed) and/or your reader will not recognize it by name, describe the use case or end result that will be meaningful to the reader instead:

Adds | (string & {}) for better autocomplete of App.SessionData

vs

✅ Improves autocompletion for session keys

New features

Begin your changeset with “Adds” to alert readers that there is something new and mention the names of any new items (options, functions) that have been added directly in the first sentence:

my-minor-changeset.md

---
'astro': minor
---
Adds a new `flamethrow` view transitions animation
<!-- -->

Additionally, describe what people are now able to do because of these additions that they could not before.

The changeset is an opportunity to call people’s attention to new things they might wish to try in their Astro project, and may include a code example showing basic usage of the new feature:

my-minor-changeset.md

---
'astro': minor
---
Adds a new, optional property `timeout` for the `client:idle` directive

This value allows you to specify a maximum time to wait, in milliseconds, before hydrating a UI framework component, even if the page is not yet done with its initial load.

This means you can delay hydration for lower-priority UI elements with more control to ensure your element is interactive within a specified time frame.

```
<Button client:idle={{ timeout: 500 }} />
```

You can also use <h4> - <h6> Markdown headings to break your longer content into sections.

Breaking changes

Changesets focus on what has changed, and must include any breaking changes, including changes to default behavior. Most users will have several default settings configured (often by not setting any value themselves), so changes to defaults can have a significant impact on someone’s project!

Verbs like “removes”, “changes”, and “deprecates” call attention to something that might require attention. Unlike a new feature someone can choose not to use, changing default or expected behavior cannot be ignored.

You can also use <h4> - <h6> Markdown headings to break your content into sections, for example, to add headings like, “What should I do?” or “Migrating from the previous version.”

my-major-changeset.md

---
'astro': major
---
Removes support for returning simple objects from endpoints. You must now return a `Response` instead.

Changeset messages for breaking changes must also provide clear guidance for updating. Diff code samples are encouraged when appropriate:

my-major-changeset.md

---
'astro': major
---
Removes support for Shiki custom language's `path` property. The language JSON file must now be imported and passed to the option instead.

```diff
// astro.config.js
+ import customLang from './custom.tmLanguage.json'

export default defineConfig({
  markdown: {
    shikiConfig: {
      langs: [
-       { path: './custom.tmLanguage.json' },
+       customLang,
      ],
    },
  },
})
```

If your contribution changes a default value, then it is helpful to describe how to revert back to the previous behavior. Readers may also appreciate being informed that they can remove configuration that is no longer needed.

my-major-changeset.md

---
'astro': major
---
Changes the default value of `security.checkOrigin` to true, which now enables Cross-Site Request Forgery (CSRF) protection by default for pages rendered on demand.

If you had previously configured `security.checkOrigin: true`, you no longer need this set in your Astro config. This is now the default and it is safe to remove.

To revert to the previous default behavior and opt out of automatically checking that the “origin” header matches the URL sent by each request, you must now explicitly set `security.checkOrigin: false`:

```diff
export default defineConfig({
+  security: {
+    checkOrigin: false
+  }
})
```

Using Markdown section headings

For longer descriptions that you want to split into sections, always start at the <h4> level, using #### where you would normally use ## in a regular Markdown post. This ensures readability when your message is incorporated into the final CHANGELOG:

my-long-changeset-with-sections.md

---
'astro': minor
---
Adds a new Sessions API to store user state between requests for on-demand rendered pages.

#### Configuring session storage
<!-- ... -->

#### Using sessions
<!-- ... -->
##### In `.astro` pages
<!-- ... -->
##### In API endpoints
<!-- ... -->

#### Upgrading from the experimental API
<!-- ... -->