List of free meta stuff for developerππ½
If you're looking for all programming tools around meta (not just free). Check this page List of meta Programming Tools

Meta Tags
With Meta Tags you can edit and experiment with your content then preview how your webpage will look on Google, Facebook, Twitter and more!
Tag: meta, SEO

Web Code Tools
The ultimate web code generators. Generate HTML, CSS, JSON-LD, Twitter Cards, Open Graph and more! No coding skills required.
Tag: html, css, JSON, meta