The formatters read text you paste and print a result in the browser. They do not open a file from disk, and they do not upload the paste. There is no account.
JSON Formatter pretty-prints or minifies JSON and shows the engine's parse error when the text is not JSON. Large JSON integers can lose precision because they pass through ordinary JavaScript numbers. XML Formatter indents a well-formed document and stops on a parse error instead of repairing the tree. HTML Escape turns special characters into entities, or back again, without rendering a page.
Regex Tester runs a JavaScript regular expression against the sample you provide. A pattern that does not compile shows the error. Cron Parser reads a five-field expression in plain English. A seconds field, month names, and nicknames such as @daily are rejected rather than guessed.
Robots.txt Generator writes a crawler file: an allow rule, disallow paths, and an optional sitemap line. The file is a request to clients, not a lock on a server. htaccess Redirect Generator prints one Apache Redirect line, either 301 or 302. It does not install that line on Apache, Nginx, or Cloudflare.
Tools
Read the privacy page for what each check sends.