Every input on a tool page is a query parameter in the address bar. Change a value and the address changes with it. Copy that address and send it to someone else, or bookmark it. Opening it later reproduces the same inputs and the same result, with no account needed.
An input left at its default value is dropped from the address, to keep a link short. Only a value the reader changed is written.
An Australian calculation always carries its edition in the address, even the default one. An AU form can read AS/NZS 3008.1.1:2025 or the superseded 2017 edition. A New Zealand calculation never carries an edition, because AS/NZS 3008.1.2 has one edition to read.
An address with no edition key reads the 2017 edition, always. A link made before AmpSize offered 2025 still returns its 2017 answer today, unchanged.
A link copied straight from a fresh tool page is a bookmark, not a save. It holds the inputs alone: no label, no project and no history of earlier revisions.
A saved calculation's own address is different. It also carries its own id, and a project id if it has one. Opening it shows the saved values. The owner's Save button then offers a revision, not a new save. Anyone else who opens the same link gets a plain Save, which makes a new calculation instead. Saving at all, from the Save button beside the result, needs a sign-in.