Free tool to check HTTP status codes

For a potential clients website I wanted to check the XML sitemap for errors. I had a suspicion the file contained links to that no longer worked (301 redirects and 404 errors) but without having access to the Search Console I had no quick way to check.
SEO tool HTTP headers
To solve this I wrote some PHP code to get the HTTP request headers of an array of URLs. I thought someone else might find it useful so after polishing it a bit I published it online.

Free SEO tool: Bulk Check HTTP status codes

Extensive /robots.txt guide for SEOs

/robots.txt extensive beginners guide
This is a “from beginner to advanced” guide to /robots.txt. Each instruction contains advice on common mistakes and pitfalls. Written for beginning SEOs and marketers but full of helpful info for people from all knowledge levels.