Plugins extend the functionality of WordPress to do almost anything you can imagine. Here we will maintain a list of our favorite WordPress plugins.

Content Management

Custom Post Type UI FREE

This is a very powerful plugin for building a web application. Custom Post Type UI allows you to create your own custom post types and taxonomies without touching any lines of code.

Posts 2 Posts FREE

This is another very powerful plugin for building a web application. This plugin allows you to create many-to-many relationships between posts, pages, and custom post types as well as many-to-many relationships between posts and users.
For example, you could use P2p to make connections between custom post types for schools, teachers, and subjects. A school could have multiple teachers, and each teacher could be tied to one or more subjects.

WP All Import PREMIUM

This plugin comes in handy if you are looking to import data into WordPress from another source that is in either an XML or CSV file, which are two formats not routinely accepted by WordPress. There is also a pro or premium version of the plugin available for purchase that extends the functionality to allow you to import data into custom post types as well as custom fields. The pro version also allows you to import images from a URL and have them saved in the media library. Another helpful feature is the ability to set up recurring imports that will periodically check a file for changes or updates and then modify the corresponding post as needed.

Developer Tools

Kint Debugger FREE

Still using print_r, var_dump, and debug_backtrace? Kint will transform the way you develop your PHP applications forever. Kint is a customizable, easy to use, powerful debugging tool which allows you to inspect variables in an organized, collapsible, human-readable format. The Kint Debugger plugin adds that functionality right into WordPress, speeding up your development time significantly.

Query Monitor FREE

Query Monitor is an absolutely invaluable tool when developing WordPress applications. Query Monitor adds a special menu to the admin bar on your site giving you an inside look at exactly what happens when you visit a WordPress page. Features include information on everything you can think of: database queries, hooks, themes, PHP errors, requests, redirects, AJAX debugging, admin screens, environment, and more.

Downloads

Easy Digital Downloads FREE

All of the ecommerce and membership plugins mentioned so far can be used for digital products and downloads as well as physical goods. However, if you are only planning on selling digital goods, you should consider Easy Digital Downloads, which was developed specifically for this use case.
Like Jigoshop, the core Easy Digital Downloads plugin is available for free in the WordPress repository, while extensions are available for purchase at the plugin’s website.

eCommerce

Jigoshop FREE

The Jigoshop ecommerce plugin is released under the GPL license and available in the WordPress plugin repository. Dozens of extensions exist for Jigoshop that do everything from add support for different payment gateways to customize your emails to conform to Norwegian tax rates.
The base plugin, which includes all of the functionality to add products and process orders is free. Most of the extensions are available for under $50 each, or you can purchase a membership to gain access to all of the extensions sold through the main Jigoshop store.

WooCommerce FREE

WooCommerce, which was forked from Jigoshop, has improved both the underlying code and the number and quality of extensions. The community is definitely behind WooCommerce in abig way as WooCommerce is quickly eclipsing Jigoshop (and ecommerce platforms in general) in terms of both user and developer adoption. WooCommerce extensions are pricier than Jigoshop extensions. The run about $150-200 each, with no membership with access to all extensions. Most important for many app developers is the fact that licenses for each individual extension must be maintained to ensure updates.

Forms

Gravity Forms PREMIUM

This plugin is an absolute must because it enables you to easily create custom contact forms for your site. It is extremely easy to create a form using the visual form editor, which allows you to drag and drop the fields you need into the form and reposition them as needed. Standard fields are included as well as the option to create your own custom fields. The forms are very flexible and can be set up as multiple page forms with progress bars. Conditional fields allow you to show or hide fields based on the user’s selections in previous fields. Another great feature of this plugin is the ability for the forms, once completed, to be forwarded anywhere as chosen by the site admin in the form settings. All in all, this plugin is extremely useful and flexible for anyone needing to create a form on their site and easy to use for someone without coding knowledge.

Maintenance

Backup Buddy PREMIUM

The Backup Buddy plugin provides you with the opportunity to back up your entire WordPress install for safekeeping, restoring, or moving your site. Backups can be scheduled on a recurring basis, and the file can then by downloaded to your computer, emailed to you, or sent off to the storage location of your choice, such as Dropbox or an FTP server. This plugin also features a restore option that will easily restore your themes, widgets, and plugins. The plugin also allows you to easily move your site to a new server or domain right from the WordPress dashboard, which comes in handy if you work on a dev server and then move the sites over to a production environment upon launch.

W3 Total Cache FREE

Caching your content is a great idea for optimizing the performance of your website. You can save a lot processing time by displaying cached pages to the end user instead of querying the database every time someone requests data. W3 Total Cache has a lot of built-in features for managing what content gets cached and when the cache should be cleared.

Membership

Paid Memberships Pro FREE

Paid Memberships Pro is a very powerful plugin which allows you to restrict content to your users based on customized Membership Levels. Only want staff members to see certain pages? No problem. Want to charge customers a monthly subscription for premium content? Piece of cake. PMPro handles it all, helping all kinds of businesses get paid by their customers.
Out of the box, PMPro supports the most popular payment gateways, tools to export and manage memberships, in depth reports, customizable discount codes, and much more!
Additionally, there are countless other “addon” plugins which allow you to integrate with many popular third party services, protect entire WordPress networks, create “drip feed” content, and much, much more.

Mobile

AppPresser PREMIUM

Want to easily build a hybrid mobile app for you or your client and don’t want to write the code for it yourself? Check out AppPresser. You can download a WordPress plugin that will allow you to build an iOS and/or Android app based off your own responsive mobile theme or a selected AppPresser theme. AppPresser is more than just a mobile theme: it can integrate with device hardware like the camera, geolocation, and amore. AppPresser-created apps can be uploaded to iTunes and Google Play so you and your clients can have a real presence in the mobile app marketplace without touching a line of Objective-C or Java.

Other

BadgeOS FREE

This plugin can transform any website into a platform for rewarding members achievements based on their activities. It allows the site admin to create different achievement types and award the members sharable badges once they complete the requirements to ear that particular achievement or achievements. Badges are Mozilla OBI compatible and sharable via Credly.com.

Security

Hide Admin Bar from Non-Admins FREE

This is a very simple plugin which does exactly what it says – hides the admin bar from non-admins. Useful when users should not normally be allowed to access the WordPress dashboard.

WP Bouncer FREE

This plugin will make sure users are only logged in from one computer or device at a time.

SEO

All in One SEO Pack FREE

This is a great plugin to use if you are concerned about SEO (search engine optimizations). This plugin was created by Semper Fi Web Design and once installed, it automatically optimizes your site for search engines. It also adds custom meta fields to each page and post that then allow you to add in custom titles as well as descriptions and keywords. There are pro or premium versions of the plugin that extend the functionality to allow for customization of search engine settings for each individual post or page as well as the option to set sitewide defaults in WordPress.

Social

BuddyPress FREE

BuddyPress is social networking in a box. You can start up a social network with most of the same features as Facebook in a matter of minutes.

Theme

Theme My Login FREE

As the title suggests, this plugin themes your login page to match your theme to create a seamless experience for the end user. However, it also includes a ton of other features including components to handle themed profiles, user moderation, custom redirection and much more.

User Management

Members FREE

Members extends the control that you have over user roles and capabilities in your site. It enables you to edit as well as create and delete user roles and capabilities. This plugin also allows you to set permissions for different user roles to determine which roles have the ability to add, edit, and/or delete various pieces of content. This is another must-have plugin for building an extensible web application because you can completely customize each user’s experience by defining and managing the roles and capabilities he will have access to.