These are tools rather than calculators. They take text instead of numbers — a JSON payload, an encoded string, a timestamp — and give it back in a shape a person can read. What they have in common is where they run: entirely in your browser, with no request to a server, because the data developers need to inspect is usually the data they are least free to send somewhere else.
Calculators in this section
Why these run in the browser
An API response pasted into a formatter is rarely anonymous. It carries customer names, order histories, internal identifiers and, more often than anyone likes to admit, a token that is still valid. A tool that posts that to a server to format it has quietly turned a debugging step into a data transfer — one that may cross a border, land in a log, and outlive the bug being chased. Doing the work locally removes the question entirely: there is nothing to retain because nothing was sent.