Small tools that do one thing, properly
No account, no sign-up, no usage limit, and the working shown on the page. Each one exists because we needed it ourselves while building the file it sits next to.
Why they are free
Because the alternative is worse for everyone. A tool that asks for an email before it answers gets used once; a tool that answers immediately gets kept in a bookmark bar, and some of the people who keep it eventually want the full file that sits behind it. That is the whole business model, written out — there is no second page where the price appears.
What that buys you: no cookie banner, because there are no cookies. No analytics, so we genuinely do not know how many of you there are. No rate limit, because we are not metering something that costs us almost nothing to serve.
Questions
Are these really free?
Yes, and there is no account to make, no email to give and no usage limit. We pay for the hosting; the paid files next to each tool are what make that worth doing. A tool that quietly stops working after three tries would be an advert for a paywall, and this is not that.
What happens to what I type?
Three of the four tools do the whole calculation inside your browser and send nothing anywhere. The domain checker has to send the domain name, because the answer is a lookup in a dataset too big to download. Nothing is logged against you, there are no cookies and no analytics on any page here. The privacy page says it tool by tool.
Do I need to buy anything to use them?
No. Each tool page links the paid file it sits next to, because that file is the same work done at full size, and somebody who liked the tool is the only person likely to want it. Ignoring it costs you nothing.
Where does the data come from?
The domain checker uses the public Common Crawl web graph. The city lookup uses an openly licensed cities dataset. Both pages name the source and the date they were built, because a number without a source is a number you cannot check.
About these free tools
Four tools, and each one answers a question people already type into a search box: how many sites link to this expired domain, how many units do I need to sell to break even, where do I plan a year of spending without a spreadsheet, and where do I get city population data as a free dataset. They are deliberately narrow. A tool that tries to do everything needs a manual, and a tool that needs a manual does not get used.
Everything runs in your browser except the domain lookup, which needs a dataset far too large to send you. That is not a design preference: this site is served from a static host with no server of its own, which turns out to be the best possible guarantee that nothing you type is being kept.