URL commitment · dated 10 September 2026

Addresses you can build on

If you link to a calculator or embed one on your website, you are relying on our addresses staying put. This page is that promise, in writing.

1. Calculator addresses are permanent

Every calculator lives at https://calculatorfox.org/<name>. Once an address is published it is never reused for something else and never deleted. If we ever retire a calculator, its address keeps answering with the nearest equivalent and a note saying so.

2. Anything that moves redirects

When a page is renamed or two duplicate pages are merged, the old address sends a permanent redirect (HTTP 301/308) to the new one. Your link keeps working and search engines follow it. Thousands of alternative names already redirect this way today.

3. Embed addresses are versioned

The embed code you copy points at https://calculatorfox.org/embed/v1/<name>. That v1 is a promise: the frame at that address keeps its current behaviour, its parameters and its resize protocol. If we ever change how embeds work in a way that would affect your page, the change ships as v2 and v1 keeps serving. The older unversioned address /embed/<name> is a permanent alias of v1.

4. The credit line is your fallback

The embed snippet places a plain link to the calculator in your page's own HTML, under the frame. If our script or our servers are ever unreachable, your readers still see a working link rather than a blank box or an error.

5. What can change

The figures a calculator returns change when the rules behind them change (a new tax year, a revised guideline); each page says which reference data it uses and when that data was last checked. Page design and the text around a calculator can change. Addresses do not.

Applies to all 1,327 calculators. Questions: contact support. See also the embed builder and how calculators are checked.