Bartosz Dziewoński wrote:

On 2016-01-11 22:06, gnosygnu wrote:

...

So, to answer your question, the IDs never change. 14640471 will always point to Mars, while 699008434 points to the 2016-01-09 revision for Mars.

While it's unlikely/rare, I think the page id can change when a page is deleted and re-created, and maybe some other cases. MediaWiki tries to keep it constant (for example, I think it's preserved after deletion and undeletion), but it's not always possible.

It looks like https://phabricator.wikimedia.org/T28123 was just fixed, so page IDs changing should now hopefully be rarer.

MZMcBride