Below is a list of my eight favorite free WordPress plugins with short descriptions listed in alphabetical order. Most of the them are generic plugins that can be used on pretty much any kinds of WP websites.
Ajax Thumbnail Rebuild
WP automatically save images in the Media Library in many different sizes such as thumbnail, medium and large. When you make changes to the size settings or add new sizes via your theme, all existing images won’t be automatically resized and re-saved. This is what the plugin does primarily, bulk resizing all existing images. It also has a setting that lets you “resize only Featured Image” so you don’t have to process everything in the Media Library.
Change WP Mail From Details
By default, when WP sends out email from the system it uses the name “WordPress” and from email address “firstname.lastname@example.org”. Using this plugin, you can change these values as easy as A-B-C.
If you ever came across a situation where you feel some widgets should appear only on selected pages without having to create countless sidebars, then this plugin is what you needed. This clever plugin allows you to control widgets display rules using conditional logic. You can define the rules based on pages, categories, tags, templates, user roles and many more! The interface may be a little daunting for starters but straightforward enough once you get the hang of it.
Enable Media Replace
This plugin adds a feature to the Media Library that should have come standard with WP (I think). It allows admins to upload and replace the original media files, not limited to images only. Without this plugin, you’d have to replace files manually via FTP or upload the file as a new Media item and then update all the links to reference to this new file. Very inconvenient!
This is a plugin I recently discovered. Its main purpose is to prevent WP from failing when someone tries to upload super-huge images like unedited digicam photos into the Media Library. In the Settings page you can limit the maximum width and height your website can accept therefore any images larger than the specified size will be resized automatically.
Jetpack is a Swiss Army knife of WP plugins. It comes with tonnes of features you probably won’t be using but the ones you are going to use are indispensable nonetheless. The most used Jetpack features for me are Contact Form, Photon, Omnisearch, WordPress.com Stats, Publicize and Shortcode Embeds.
Widget CSS Classes
With this plugin you can specify custom CSS classes to any widgets. WP by default adds a bunch of CSS classes to widgets but they aren’t that reliable if you are doing heavy customizations on your theme. This plugin provides a simple but powerful feature that gives you a lot of flexibility in your themes customization work.
Yoast SEO has to be the most popular SEO plugin for WP, and it should. It doesn’t matter whether or not you’re serious about SEO, this plugin is a must.
I hope you’ll find this list useful!