A while ago, I wrote about how you can add custom classes to your widgets. I’ve also created a plugin that’s available in WPORG but haven’t been updated in a while.
I’m announcing a new plugin, Widget Attributes, that you can use to add custom attributes to your widgets. Currently, it only supports the ID and classes and maybe will support adding custom attributes in the future. For now, you can download it from here. I’m submitting this plugin to WPORG and will retire the old one (I don’t like the name) and will update this post once it’s approved.
The plugin is now live!