nixtool

Nix Image Optimizer helps optimize your WordPress media library by converting supported image uploads to WebP automatically and giving you tools to manage existing images, generate lightweight featured images, and improve image SEO metadata.
Features:
<ul>
<li>Automatically converts new JPG, JPEG, PNG, and AVIF uploads to WebP.</li>
<li>Bulk-compresses existing Media Library images.</li>
<li>Shows compression statistics in a Media Log.</li>
<li>Adds optional watermark support before compression.</li>
<li>Generates blog-style featured images from post title, category, author name, and avatar.</li>
<li>Supports custom featured image background colors, gradients, typography, and output dimensions.</li>
<li>Auto-fills missing image ALT text and attachment descriptions from post content.</li>
<li>Includes Basic and Advanced Image SEO Metadata modes.</li>
<li>Scans and backfills existing posts with safe generated-metadata rules.</li>
<li>Includes an unused media scanner and cleaner.</li>
<li>Works with WordPress Media Library metadata and regeneration flow.</li>
</ul>
<h3>External services</h3>
This plugin can connect to the WordPress avatar system, which commonly uses Gravatar, when the Featured Image Generator is configured to include the post author’s avatar.
When the avatar option is enabled, the plugin requests the author’s avatar URL while showing the featured-image preview in the WordPress admin and while generating a featured image for a post or page. WordPress builds that avatar URL from the author’s user account email address according to the site’s normal avatar settings. The plugin downloads the avatar image from that URL so it can draw the circular author avatar into the generated featured image. If the avatar option is disabled, or if no avatar URL is available, the plugin does not request the avatar image and uses a local placeholder shape instead.
The avatar service is provided by Gravatar/Automattic: 
Terms of Service: https://wordpress.com/tos/ 
Privacy Policy: https://automattic.com/privacy/

Nix Image Optimizer

Convert images to WebP with bulk compression, media log, watermarking, image SEO, featured image generation, and unused media cleanup.

JS Morisset

<h3>Complete Schema Markup and Meta Tags for WordPress</h3>
Present your content at its best for social sites and search results, no matter how URLs are shared, reshared, messaged, posted, embedded, or crawled.

The most comprehensive and accurate Schema markup plugin for WooCommerce products.
Supports over 500 different Schema types and sub-types (including WooCommerce offers for Schema Books, Events, Products, Product Groups, and Services).
Provides complete Schema markup and meta tags for:
<ul>
<li>Facebook / Open Graph</li>
<li>Google Knowledge Graph</li>
<li>Google Merchant Feed XML</li>
<li>Google Rich Results / Rich Snippets</li>
<li>Image and Video SEO</li>
<li>Instagram Catalog Feed XMLs</li>
<li>Meta (Facebook and Instagram) Catalog Feed XMLs</li>
<li>Mobile Web Browsers</li>
<li>oEmbed for LinkedIn, Discord, and Drupal</li>
<li>Pinterest Rich Pins</li>
<li>Schema JSON-LD Markup</li>
<li>Slack</li>
<li>WhatsApp and Messaging Apps</li>
<li>WordPress REST API</li>
<li>WordPress Sitemaps XML</li>
<li>X (Twitter) Cards</li>
</ul>

Fixes all Google Rich Results and Google Merchant errors, including:
<ul>
<li>A value for the headline field is required</li>
<li>A value for the image field is required</li>
<li>A value for the logo field is required</li>
<li>A value for the publisher field is required</li>
<li>Either “price” or “priceSpecification” should be specified (in “offers”)</li>
<li>Invalid value in field “priceSpecification”</li>
<li>The aggregateRating field is recommended</li>
<li>The brand field is recommended</li>
<li>The headline field is recommended</li>
<li>The image field is recommended</li>
<li>The review field is recommended</li>
<li>Missing field “address”</li>
<li>Missing field “aggregateRating”</li>
<li>Missing field “brand”</li>
<li>Missing field “businessDays”</li>
<li>Missing field “cutoffTime”</li>
<li>Missing field “deliveryTime”</li>
<li>Missing field “hasMerchantReturnPolicy” (in “offers”)</li>
<li>Missing field “image”</li>
<li>Missing field “priceRange”</li>
<li>Missing field “review”</li>
<li>Missing field “shippingDetails” (in “offers”)</li>
<li>Missing field “telephone”</li>
<li>No global identifier provided (e.g. gtin mpn isbn)</li>
<li>Not a known valid target type for the itemReviewed property</li>
<li>Price Mismatched value (page crawl): (price [price])</li>
</ul>
Optimized image sizes for social sites and search engines:
<ul>
<li>Commerce Manager Catalog Feed XML (Facebook and Instagram)</li>
<li>Google Merchant Feed XML</li>
<li>Open Graph (Facebook and oEmbed)</li>
<li>Pinterest Pin It</li>
<li>Schema 1:1 (Google Rich Results)</li>
<li>Schema 4:3 (Google Rich Results)</li>
<li>Schema 16:9 (Google Rich Results)</li>
<li>Schema Thumbnail</li>
<li>Video Preview Image</li>
<li>X (Twitter) Summary Card</li>
<li>X (Twitter) Summary Card Large Image</li>
</ul>
Reads additional information from active plugins, including:
<ul>
<li><a href="https://wordpress.org/plugins/co-authors-plus/" rel="ugc">Co-Authors Plus</a></li>
<li><a href="https://wordpress.org/plugins/elementor/" rel="ugc">Elementor Website Builder</a></li>
<li>Gravity Forms</li>
<li>Gravity View</li>
<li><a href="https://wordpress.org/plugins/jetpack/" rel="ugc">Jetpack</a></li>
<li><a href="https://wordpress.org/plugins/jetpack-boost/" rel="ugc">Jetpack Boost</a></li>
<li><a href="https://wordpress.org/plugins/judgeme-product-reviews-woocommerce/" rel="ugc">Judge.me Product Reviews for WooCommerce</a></li>
<li><a href="https://wordpress.org/plugins/wp-retina-2x/" rel="ugc">Perfect Images</a></li>
<li><a href="https://wordpress.org/plugins/perfect-woocommerce-brands/" rel="ugc">Perfect Brands for WooCommerce</a></li>
<li><a href="https://wordpress.org/plugins/polylang/" rel="ugc">Polylang</a></li>
<li>Product GTIN (EAN, UPC, ISBN) for WooCommerce</li>
<li><a href="https://wordpress.org/plugins/publishpress-authors" rel="ugc">PublishPress Authors</a></li>
<li>qTranslate-XT</li>
<li><a href="https://wordpress.org/plugins/rate-my-post/" rel="ugc">Rate my Post</a></li>
<li><a href="https://wordpress.org/plugins/simple-job-board/" rel="ugc">Simple Job Board</a></li>
<li><a href="https://wordpress.org/plugins/the-events-calendar/" rel="ugc">The Events Calendar</a></li>
<li><a href="https://wordpress.org/plugins/ultimate-member/" rel="ugc">Ultimate Member</a></li>
<li><a href="https://wordpress.org/plugins/woocommerce/" rel="ugc">WooCommerce</a></li>
<li>WooCommerce Brands</li>
<li>WooCommerce Currency Switcher</li>
<li>WooCommerce UPC, EAN, and ISBN</li>
<li><a href="https://wordpress.org/plugins/wp-job-manager/" rel="ugc">WP Job Manager</a></li>
<li><a href="https://wordpress.org/plugins/wp-postratings/" rel="ugc">WP-PostRatings</a></li>
<li>WP Product Review</li>
<li><a href="https://wordpress.org/plugins/wp-recipe-maker/" rel="ugc">WP Recipe Maker</a></li>
<li>WPML</li>
<li><a href="https://wordpress.org/plugins/yith-woocommerce-brands-add-on/" rel="ugc">YITH WooCommerce Brands Add-on</a></li>
<li><a href="https://wordpress.org/plugins/yotpo-social-reviews-for-woocommerce/" rel="ugc">Yotpo Social Reviews for WooCommerce</a></li>
</ul>
Supports additional WooCommerce product attributes:
<ul>
<li>Book Author Name</li>
<li>Book ISBN</li>
<li>Product Adult Type</li>
<li>Product Age Group</li>
<li>Product Availability</li>
<li>Product Brand</li>
<li>Product Google Category ID</li>
<li>Product Color</li>
<li>Product Condition</li>
<li>Product Currency</li>
<li>Product Energy Rating</li>
<li>Product Fluid Volume</li>
<li>Product GTIN-14</li>
<li>Product GTIN-13 (EAN)</li>
<li>Product GTIN-12 (UPC)</li>
<li>Product GTIN-8</li>
<li>Product GTIN</li>
<li>Product Net Height</li>
<li>Product ISBN</li>
<li>Product Net Len. / Depth</li>
<li>Product Material</li>
<li>Product MPN</li>
<li>Product Min Advert Price</li>
<li>Product Pattern</li>
<li>Product Price</li>
<li>Product Price Type</li>
<li>Product SKU</li>
<li>Product Shipping Height</li>
<li>Product Shipping Length</li>
<li>Product Shipping Weight</li>
<li>Product Shipping Width</li>
<li>Product Size</li>
<li>Product Size Group</li>
<li>Product Size System</li>
<li>Product Target Gender</li>
<li>Product Net Weight</li>
<li>Product Net Width</li>
</ul>
Optionally improves the structured data markup of other SEO plugins:
WPSSO Core and its add-ons can also run in combination with other SEO plugins to improve their performance and structured data markup.
<ul>
<li>All in One SEO Pack</li>
<li>Rank Math SEO</li>
<li>SEOPress</li>
<li>The SEO Framework</li>
<li>WP Meta SEO</li>
<li>Yoast SEO</li>
</ul>
Premium edition can retrieve data from service APIs automatically, including:
<ul>
<li>Bitly Short URL</li>
<li>DLMY.App Short URL</li>
<li>Facebook Video Data</li>
<li>Gravatar Image Data</li>
<li>Judge.me Review Data</li>
<li>Ow.ly Short URL</li>
<li>Shopper Approved Review Data</li>
<li>Slideshare Presentation Data</li>
<li>Soundcloud Track Data</li>
<li>Stamped.io Review Data</li>
<li>TinyURL Short URL</li>
<li>Vimeo Video Data</li>
<li>Wistia Video Data</li>
<li>WP Media Library Video Block Data</li>
<li>WP Media Library Video Shortcode Data</li>
<li>Your Own URL Shortener (YOURLS) Short URL</li>
<li>YouTube Video and Playlist Data</li>
</ul>

WPSSO Core – Complete Schema Markup and Meta Tags

Present your content at its best for social sites and search results, no matter how URLs are shared, reshared, messaged, posted, embedded, or crawled.

Nix Image Optimizer vs WPSSO Core – Complete Schema Markup and Meta Tags