ckeditor plugin does not exist

This is probably a duplicate of 💬 ckeditor5 PlugIn Not Found Exception Closed: works as designed . There is nothing to distinguish them.

You updated to Drupal 10 from Drupal 9 and were still using CKEditor 4 instead of CKEditor 5. That's why this happened.

See the big text in the release: https://www.drupal.org/project/drupal/releases/10.0.0#cke5 → .

I agree the UX is not great. I advocated for something better at #3304736-43: Provide a good UX to ensure the CKEditor 4 to 5 update is always done before upgrading to Drupal 10 unless the contrib module is installed → but never managed to convince core committers. Bumped it, referencing this issue: #3304736-50: Provide a good UX to ensure the CKEditor 4 to 5 update is always done before upgrading to Drupal 10 unless the contrib module is installed → .

Glad I kept the 9.5 setup in another directory with that working database. I renamed it active for Apache, upgraded to CKeditor5, did the configuration, uninstalled CKeditor 4, copied the database to a new name with phpMyadmin, changed the database name to that in settings.php, ran update.php and 39 databdase updates later, it was all working properly

Thanks for the prompt reply how to fix it.

Lovely — sounds like you had zero problems with the update process then? 😄

Automatically closed - issue fixed for 2 weeks with no activity.

The CKEditor 4 still exists in the core extension and dependency is not yet transferred.
you can do composer require 'drupal/ckeditor:^1.0' to keep CKEditor
or change all CKEditor4 dependent config to ckeditor5 after enabling ckeditor5.

By not first changing all formats to ckeditor5 before upgrading to 10, this will essentially lock users out selecting a format after upgrading. Trying to change them after the fact, you can't even get to the page, without reaching the Drupal\Component\Plugin\Exception\PluginNotFoundException: The "ckeditor" plugin does not exist.

This just smacks of an annoying archetypal drupalism that can frustrate unexperienced devs... if the plugin doesn't exist, it shouldn't just crash the site. It should handle it elegantly in such a way that at least allows the user to select a plugin that DOES exist. No disrespect to anyone's hard work, I know this isn't easy stuff.

I upgraded to 10.2.2.

Here's what worked for me:

1. Install CKEditor 4 (If not already installed): composer require 'drupal/ckeditor:^1.0'
2. Disable CKEditor 5 from UI
3. drush cr
4. Checked there were now no errors in Text Formats.
5. Enabled CKEditor 5 in UI
6. drush cr
7. Changed from CKEditor to to CKEditor5 in Text Formats
8. Checked and all looked fine (no errors)
9. Disabled and fully uninstalled CKEditor4 (UI + composer remove drupal/ckeditor)
10. drush cr

Done!