How these tools treat your data
Tools in the first group look at the request your own browser sends, so they describe you and nobody else. The calculators and converters (subnets, MAC prefixes, Punycode, email headers, browser features) do all of their work inside the page; what you type stays on your device. The DNS lookup sends its question from your browser straight to the public resolver you choose. The WHOIS lookup and the security headers check are the only ones that ask iseeu.cc's server to contact another system for you: the registry or website sees a request from Cloudflare's network rather than from you, each IP address gets ten such requests a minute, and nothing about the request is kept. The privacy page has the details for each tool.
Developers and AI agents can reach the same data without a browser through plain-text and JSON endpoints and an MCP server, described on the API page.