Remove IE support from Twenty Twenty-One

[sabernhardt]

• Removes polyfill scripts, but continues to register their handles.
• Removes IE-specific styles from the main stylesheet.
• Removes the separate IE stylesheets from the build process and from enqueuing functions.
• Removes or replaces contents of the unused files.
• Removes the is-IE class.

Props: iflairwebtechnologies

Trac 64590

---

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Core Committers: Use this line as a base for the props when committing in SVN:

Props sabernhardt.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

Test using WordPress Playground

The changes in this pull request can previewed and tested using a WordPress Playground instance.

WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Some things to be aware of

• The Plugin and Theme Directories cannot be accessed within Playground.
• All changes will be lost when closing a tab with a Playground instance.
• All changes will be lost when refreshing the page.
• A fresh instance is created each time the link below is clicked.
• Every time this pull request is updated, a new ZIP file containing all changes is created. If changes are not reflected in the Playground instance,
  it's possible that the most recent build failed, or has not completed. Check the list of workflow runs to be sure.

For more details about these limitations and more, check out the Limitations page in the WordPress Playground documentation.

Test this pull request with WordPress Playground.

[westonruter]

So good to remove all this!

[Copilot]

Pull request overview

This PR removes Internet Explorer support from the Twenty Twenty-One WordPress theme. IE11 reached end-of-life in 2022, making this cleanup appropriate for WordPress core themes.

Changes:

• Removed IE-specific stylesheets and SASS imports from build process
• Deprecated IE class detection function and removed its action hook
• Registered empty polyfill script handles for backward compatibility
• Removed polyfill dependencies from navigation and embed scripts

Reviewed changes

Copilot reviewed 8 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
functions.php	Removed IE stylesheet logic, registered empty polyfill handles, removed polyfill dependencies, deprecated twentytwentyone_add_ie_class() function and removed its action hook
package.json	Removed build:ie and build:ie-editor npm scripts
style.css	Removed 58 lines of IE-specific CSS targeting .is-IE class
style-rtl.css	Removed 58 lines of IE-specific RTL CSS
style.css.map	Updated source map to reflect removed IE utilities
assets/sass/style.scss	Removed import of 07-utilities/ie
assets/sass/07-utilities/ie.scss	Replaced IE styles with comment indicating removal
assets/js/polyfills.js	Replaced polyfills with comment indicating removal
assets/css/ie.css.map	Replaced with empty map
assets/css/ie-editor.css	Replaced with comment indicating removal

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.