1. Beaver Builder Plugin
Beaver Builder is a flexible drag and drop page builder that works on the front end of your WordPress website. Whether you're a beginner or a professional, you're going to love taking control of your website. Stop writing HTML or wrestling with confusing shortcodes. With Beaver Builder, building beautiful, professional WordPress pages is as easy as dragging and dropping.

2. Contact Form 7
Contact Form 7 can manage multiple contact forms, plus you can customize the form and the mail contents flexibly with simple markup. The form supports Ajax-powered submitting, CAPTCHA, Akismet spam filtering and so on.
Just another contact form plugin. Simple but flexible.

3. Real Time Find and Replace
This plugin allows you to dynamically (i.e. at the time when a page is generated) replace code and text from themes and other plugins with code and text of your choosing before a page is delivered to a user's browser.
Because the find and replace happens in real-time no changes are needed to plugins or themes which means upgrades remain easy!

4. Google Analytics
Google Analytics plugin from ShareThis is the best way to add GA tracking code to your website without modifying any files. Just log in with Google right from your WP admin dashboard and choose which website you want to link. Then you can disable GA tracking of specific users, so that when you are browsing your own site it won't affect your analytics.

Also, you will be able to see Google Analytics reports in the same interface you already use every day to write and manage your posts - in your WordPress dashboard. Now you can stay informed on how your website is doing without having to log into a separate tool.

This Google Analytics plugin has a unique feature called Trending Content. It learns about your traffic patterns and shows you a list of content that is performing significantly better than average, so that you know what resonates with your audience the most. You can even sign up to receive alerts via email or Slack when content is taking off!

One more thing - unlike other plugins, Google Analytics for WordPress has no monthly fees, and no paid upgrades. All the features are totally free

5. iThemeSecurity
Themes Security (formerly Better WP Security) gives you over 30+ ways to secure and protect your WordPress site. On average, 30,000 new websites are hacked each day. WordPress sites can be an easy target for attacks because of plugin vulnerabilities, weak passwords and obsolete software.

Most WordPress admins don't know they're vulnerable, but iThemes Security works to lock down Wordpress, fix common holes, stop automated attacks and strengthen user credentials. With advanced features for experienced users, our WordPress security plugin can help harden WordPress.

6. UpdraftPlus
UpdraftPlus simplifies backups (and restoration). Backup into the cloud (Amazon S3 (or compatible), Dropbox, Google Drive, Rackspace Cloud, DreamObjects, FTP, Openstack Swift, UpdraftPlus Vault and email) and restore with a single click. Backups of files and database can have separate schedules. The paid version also backs up to Microsoft OneDrive, Microsoft Azure, Google Cloud Storage, SFTP, SCP, and WebDAV.

7. The Social Media Widget
The Social Media Widget is a simple sidebar widget that allows users to input their social media website profile URLs and other subscription options to show an icon on the sidebar to that social media site and more that open up in a separate browser window.

8. SumoMe
Most blogs are designed for hit-and-run readers. People find your blog, read your article, and leave. Wouldn't it be nice if some of those people subscribed or shared your amazing post?

Sumo provides free tools you need to grow your WordPress site. This plugin will make it easy for your readers to join your email list, share your articles, and optimize with analytics. The free tools include:

List Builder will let you create a fancy lightbox pop up to build email subscriptions (for MailChimp, Aweber, Constant Contact, Campaign Monitor, GetResponse, ActiveCampaign, MyEmma, Mad Mimi, Infusionsoft, Feedblitz, HubSpot, MyNewsletterBuilder, Inbox First, Sailthru, Klaviyo, Vero, Pardot, Zapier, Ontraport, ExactTarget, Vertical Response, Drip, MailerLite, WhatCounts, ConvertKit, MailJet, Maropost, and others).

Share makes it insanely easy for people to share your content on mobile or web.

Welcome Mat displays a full-screen call-to-action that shows when visitors land on your site.

Heat Maps help you see where people are clicking (or not clicking) on your website.

Scroll Box is an email collection box triggered by how far your reader makes it down the screen.

Smart Bar is a Floating Bar that can appear at the top or bottom of your website. You can encourage people to subscribe to your newsletter, go to a specific page or follow you on your social networks.

Highlighter makes it easy to click to tweet about your article by selecting popular parts of your writing (like Kindle and Medium).

Image Sharer makes it simple to share your images (with a link to your post) on Pinterest, Facebook and Twitter.

And even more great free tools in our Sumo Store.

Now, people will find your blog, read your article, share your article on Twitter/Facebook/Pinterest, and subscribe via email to your email newsletter.

9. Yoast SEO
WordPress out of the box is already technically quite a good platform for SEO. This was true when Joost wrote his original WordPress SEO article in 2008 (updated every few months) and it's still true today, but that doesn't mean you can't improve it further! This plugin is written from the ground up by Joost de Valk and his team at Yoast to improve your site's SEO on all needed aspects. While this Yoast SEO plugin goes the extra mile to take care of all the technical optimization, more on that below, it first and foremost helps you write better content. Yoast SEO forces you to choose a focus keyword when you're writing your articles, and then makes sure you use that focus keyword everywhere.

Premium Support The Yoast team does not always provide active support for the Yoast SEO plugin on the WordPress.org forums. One-on-one email support is available to people who bought the Premium Yoast SEO plugin only. Note that the Premium SEO plugin has several extra features too, including the option to have multiple focus keywords and a redirect manager, so it might be well worth your investment!

You should also check out the Yoast Local SEO, Yoast News SEO and Yoast Video SEO extensions to Yoast SEO. These of course come with support too.

Bug Reports Bug reports for Yoast SEO are welcomed on GitHub. Please note GitHub is not a support forum, and issues that aren't properly qualified as bugs will be closed.

Write better content with Yoast SEO

Using the snippet preview, you can see a rendering of what your post or page will look like in the search results, whether your title is too long or too short, and whether your meta description makes sense in the context of a search result. This way the plugin will help you not only increase rankings but also increase the click through rate for organic search results.

Page Analysis

The Yoast SEO plugins Page Analysis functionality checks simple things you're bound to forget. It checks, for instance, if you have images in your post and whether they have an alt tag containing the focus keyword for that post. It also checks whether your posts are long enough, whether you've written a meta description and if that meta description contains your focus keyword, if you've used any subheadings within your post, etc. etc.

The plugin alsgruo allows you to write meta titles and descriptions for all your category, tag and custom taxonomy archives, giving you the option to further optimize those pages.

Combined, this plugin makes sure that your content is the type of content search engines will love!

Technical WordPress Search Engine Optimization

While out of the box WordPress is pretty good for SEO, it needs some tweaks here and there. This Yoast SEO plugin guides you through some of the settings needed, for instance by reminding you to enable pretty permalinks. But it also goes beyond that, by automatically optimizing and inserting the meta tags and link elements that Google and other search engines like so much:

Meta & Link Elements

With the Yoast SEO plugin you can control which pages Google shows in its search results and which pages it doesn't show. By default, it will tell search engines to index all of your pages, including category and tag archives, but to only show the first pages in the search results. It's not very useful for a user to end up on the third page of your "personal" category, right?

WordPress itself only shows canonical link elements on single pages, but Yoast SEO makes it output canonical link elements everywhere. Google has recently announced they would also use rel="next" and rel="prev" link elements in the head section of your paginated archives. This plugin adds those automatically. See this post for more info.

XML Sitemaps

The Yoast SEO plugin has the most advanced XML Sitemaps functionality in any WordPress plugin. Once you check the box, it automatically creates XML sitemaps and notifies Google & Bing of the sitemaps' existence. These XML sitemaps include the images in your posts & pages too, so that your images may be found better in the search engines too.

These XML Sitemaps will even work on large sites, because of how they're created, using one index sitemap that links to sub-sitemaps for each 1,000 posts. They will also work with custom post types and custom taxonomies automatically, while giving you the option to remove those from the XML sitemap should you wish to.

Because of using XSL stylesheets for these XML Sitemaps, the XML sitemaps are easily readable for the human eye too, so you can spot things that shouldn't be in there.

RSS Optimization

Are you being outranked by scrapers? Instead of cursing at them, use them to your advantage! By automatically adding a link to your RSS feed pointing back to the original article, you're telling the search engine where they should be looking for the original. This way, the Yoast SEO plugin increases your own chance of ranking for your chosen keywords and gets rid of scrapers in one go!

Breadcrumbs

If your theme is compatible, and themes based on for instance Genesis or by WooThemes often are, you can use the built-in Breadcrumbs functionality. This allows you to create an easy navigation that is great for both users and search engines, and will support the search engines in understanding the structure of your site.

Making your theme compatible isn't hard either, check these instructions.

Edit your .htaccess and robots.txt file

Using the built-in file editor, you can edit your WordPress blog's .htaccess and robots.txt file, giving you direct access to the two most powerful files, from an SEO perspective, in your WordPress install.

Social Integration

SEO and Social Media are heavily intertwined. That's why this plugin also comes with a Facebook OpenGraph implementation and will soon also support Google+ sharing tags.

Multi-Site Compatible

The Yoast SEO plugin, unlike some others, is fully Multi-Site compatible. The XML Sitemaps work fine in all setups and you even have the option, in the Network settings, to copy the settings from one blog to another, or make blogs default to the settings for a specific blog.

Import & Export functionality

If you have multiple blogs, setting up plugins like this one on all of them might seem like a daunting task. Except that it's not, because what you can do is simple: you set up the plugin once. You then export your settings and simply import them on all your other sites. It's that simple!

Import functionality for other WordPress SEO plugins

If you've used All In One SEO Pack or HeadSpace2 before using this plugin, you might want to import all your old titles and descriptions. You can do that easily using the built-in import functionality. There's also import functionality for some of the older Yoast plugins, like Robots Meta and RSS footer.

Should you have a need to import from another SEO plugin to Yoast SEO, or from a theme like Genesis or Thesis, you can use the SEO Data Transporter plugin, which will easily convert your SEO meta data from and to a whole set of plugins like Platinum SEO, SEO Ultimate, Greg's High Performance SEO, and themes like Headway, Hybrid, WooFramework, Catalyst etc.

10. Wordfence Security
Secure your WordPress website with Wordfence. Powered by the constantly updated Threat Defense Feed, our Web Application Firewall stops you from getting hacked. Wordfence Scan leverages the same proprietary feed, alerting you quickly in the event your site is compromised. Our Live Traffic view gives you real-time visibility into traffic and hack attempts on your WordPress website. A deep set of additional tools round out the most complete WordPress security solution available.

With over 22 million downloads, Wordfence is the most popular WordPress security plugin available. Wordfence Security is 100% free and open source. We also offer a Premium API key that gives you Premium Support, Country Blocking, Scheduled Scans, Password Auditing, real-time updates to the Threat Defense Feed, two-factor authentication, and we even check if your website IP address is being used to Spamvertize.

Bonuses

11. WP-Sweep
WP-Sweep allows you to clean up unused, orphaned and duplicated data in your WordPress. It cleans up revisions, auto drafts, unapproved comments, spam comments, trashed comments, orphan post meta, orphan comment meta, orphan user meta, orphan term relationships, unused terms, duplicated post meta, duplicated comment meta, duplicated user meta and transient options. It also optimizes your database tables.

12. WP Smush
Resize, optimize and compress all of your images with the incredibly powerful and 100% free WordPress image smusher, brought to you by the superteam at WPMU DEV!

Now with image resizing! Set a max width and height and large images will scale down as they are being compressed.

Our servers do all the heavy lifting. Strip hidden bulky information from your images and reduce file size without losing quality.

Large image files may be slowing down your site without you even knowing it. WP Smush uses WPMU DEV’s super servers to quickly smush every single one of your images and cuts all the unnecessary data without slowing down your site.

WP Smush meticulously scans every image you upload – or have already added to your site – cuts all the unnecessary data and scales it for you before adding it to your media library.

13. Simple Social Icons
Simple Social Icons is an easy to use, customizable way to display icons that link visitors to your various social profiles. With it, you can easily choose which profiles to link to, customize the color and size of your icons, as well as align them to the left, center, or right, all from the widget form (no settings page necessary!).

Great post, here are also Top 10 Blogs That Are Using WordPress platform on their website.