Antonio Lamorgese

Image ALT Fixer automatically sets the ALT attribute content of all IMG and FIGURE tags, present in a post, with a keyphrase calculated based on the post content.
<h3>Support</h3>
Please submit bugs, patches, and feature requests to:
[https://github.com/antoniolamorgese/image-alt-fixer]

Image ALT Fixer

Image ALT Fixer automatically sets the ALT attribute content of all IMG and FIGURE tags, present in a post, to improve SEO and always ensure your auth …

Kamer DINC

Compatible with the most popular plugins. Please report if you faced any problem with any plugin. 
Inserts automatically alt tag/attributes to HTML if alt attributes are empty or somehow missing. 
Works only in single page.
Note: This plugin is written only in PHP. So you can except a better SEO visibility and better crawl statistics.
Credits

WP Auto Alt Image Tag

(PHP Way) This plugin insert to html missing image alt tags/attributes based on each attachment title or filename.

Image ALT Fixer vs WP Auto Alt Image Tag