Widget CSS Classes的作者是C.M. Kendrick,目前有100,000+个有效安装。已经Tested with 5.4.1版本的wordpress。
Widget CSS Classes gives you the ability to add custom classes and ids to your WordPress widgets
Please note that this plugin doesn’t enable you to enter custom CSS. You’ll need to edit your theme’s style.css or add another
plugin that allows you to input custom CSS.
This plugin also adds additional classes to widgets to help you style them easier:

widget-first: added to the first widget in a sidebar
widget-last: added to the last widget in a sidebar
widget-odd: added to odd numbered widgets in a sidebar
widget-even: added to even numbered widgets in a sidebar
widget-#: added to every widget, such as widget-1, widget-2


Adds a text field to a widget for defining a class
You can specify multiple classes by putting a space between them
Optionally adds checkboxes with predefined classes
Optionally adds a text field to add an id to a widget
Adds first and last classes to the first and last widget instances in a sidebar
Adds even/odd classes to widgets
Adds number classes to widgets
Fully translatable
Multi-site compatible
Compatible with Widget Logic, Widget Context, and WP Page Widget plugins
Has filters and hooks for customizing output including class names

Plugin Website

Adding Custom CSS Classes to WordPress Widgets
Add .first & .last CSS Class Automatically To WordPress Widgets
Widget Context compatibility fix provided by Joan Piedra
Slovak translation by Branco WebHostingGeeks.com
Polish translation added, Slovak translation files renamed by Tomasz Wesołowski
Spanish translation by Maria Ramos at WebHostingHub
Serbo-Croatian translation by Borisa Djuraskovic at WebHostingHub
Dutch translation and predefined classes fix by Jory Hogeveen at Keraweb
Russian translation by Наталия Завьялова
Swedish translation by Olle Gustafsson
Fix ids notice by Ricardo Lüders

GitHub Contributors