Resultant.tools offers a collection of free engineering calculators and diagram tools aimed at undergraduate students. It covers everything from free body diagrams to Mohr's circle, and it doesn't ask you to sign up or pay. So the practical question for most visitors is straightforward: is it safe to use, and is the site what it claims to be?
On the technical side, the site scores well. It uses modern encryption, blocks clickjacking, and sets a content security policy — all signs that someone competent is maintaining the server. The legal pages (privacy policy, terms of service, and a business entity disclosure) are present and correct, which is more than many free tool sites bother with.
What's less clear is who exactly runs it. The domain's ownership is hidden because the .tools TLD doesn't expose WHOIS data in a standard way, and the site doesn't list a direct email or phone number on the homepage. That's not unusual for a small educational project, but it does mean you can't easily verify the operator's identity if you wanted to. There are no resultant.tools reviews elsewhere online yet, and no social media presence to cross-reference.
For its intended purpose — running browser-based engineering calculations with no data submission — the site is fine. If it ever asks for your email or personal information, treat that new request with more caution than you would the current no-strings offering.