Ayesh Karunaratne

Fast 404 is a low foot-print plugin that quickly inspects an incoming HTTP request, and terminates the request as soon as possible if the request is for a non-existing resource. If the browser is expecting an HTML page (indicated by the <code>Accept</code> HTTP header), this plugin will not intercept it. For all other requests, this plugin will terminate it immediately, saving server resources and bandwidth.
When a user browser requests a resource (such as a <code>jpg</code> image, or a <code>.woff2</code> font file), the web server sends this resource if it is available in the requested location. If the file does not exist, the request is forwarded to WordPress to handle. Unless you are using a plugin that dynamically generates these files, these file-not-found requests trigger a full WordPress Page-Not-Found error page. This plugin inspects such incoming requests, and if the browser indicates that it is looking for a resource other than an HTML page, this plugin terminates the request as soon as possible to prevent WordPress from serving this request which would be a waste of resources and bandwidth. This plugin carefully makes sure that the short-circuited 404 pages (which just shows “Not Found” on a blank page) is only returned to browser asset requests, and not for end users who expect an HTML page.
By default, all HTTP requests to <code>js|css|jpg|jpeg|gif|png|webp|ico|exe|bin|dmg|woff|woff2</code> extensions will be fast 404’d. You can configure the extensions and even configure an exclusion pattern to prevent this plugin from intercepting certain requests.
This plugin is the WordPress port of <a href="https://github.com/PHPWatch/Fast404" rel="nofollow ugc">PHPWatch/Fast404</a> package.

Fast 404

Prevents WordPress from delivering full Page-Not-Found errors when the browser is not expecting a full HTML page. Saves bandwidth and improves perform …

Yoast

Remkus de Vries

Redirectioner allows WordPress admins to have control over their dead links and redirects from inside the admin panel. <a href="https://redirectioner.com" rel="nofollow ugc">Redirectioner</a> records all URLs that users have visited and allows the admin to easily create 301 and 302 redirects to valid pages on their site. Redirects can also be created based on the best possible match for the URL the visitor was most likely trying to reach.
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Support & Bug Reports 
 If you’re in need of support or would like to file a bug report, please head over to our Github repository and <a href="https://github.com/thememix/redirectioner/issues" rel="nofollow ugc">create a new issue.</a>
</blockquote>
<h4>Features:</h4>
<ul>
<li>Get list of 404 URLs as they happen inside the admin panel</li>
<li>Easily redirect 404 URLs to existing pages or choose to ignore the 404 error</li>
<li>Provides the ability to automatically create redirects based on the URL the visitor was most likely trying to visit</li>
<li>Provide visitors with a list of suggested pages on the 404 page when a automatic redirect can not be made</li>
<li>Ability to suggest tag and category pages</li>
<li>Ability to create automatic redirect for misspelled tag and category pages</li>
<li>Ability to view logs of hits to 404 pages and redirects including referrer data</li>
<li>Ability to remove automatically remove redirects when the URL matches a new page or post permalink</li>
<li>Ability to automatically remove manual and automatic redirects once they are no longer being used</li>
<li>All features work with both pages and posts</li>
<li>Create automatic redirects for any URL resolving to a single page or post that isn’t the current permalink</li>
<li>Basic stats of plugin usage</li>
</ul>
Convert your 404 traffic by providing your site visitors with a better browsing experience and eliminate 404 URLs on your site.

Redirectioner

Creates automatic redirects for 404 traffic and page suggestions when matches are not found providing better service to your web visitors.

Fast 404 vs Redirectioner