Contact
One email address, read by the person who built the tool. No form, no ticket system, no chatbot.
That address goes to the 365i support desk, where I read it. Useful things to send: a bug, with the share link that reproduces it; a correction to a docs page, with the source you checked; a shadow you have made that you think deserves an example page; or a browser you found something broken in. Replies come from a person and usually within a working day.
What not to send
Nothing personal is needed to use the tool, so please do not send account details or anything sensitive; there are no accounts. Link exchange requests and guest post offers are deleted unread.
The company
Box Shadow Generator is published by BSolve IT Limited, trading as 365i, company number 04607330, VAT GB 806 170 747, registered in England and Wales. Based in Kettering, Northamptonshire.
Sister sites
The same company runs these, and each has its own contact route for its own subject: