In summer 2019, Facebook drastically curtailed its Graph Search feature, which had allowed users to unearth large amounts of information. A number of free online tools had made use of the feature, and stopped working.
What followed has been a game of cat and mouse, as the creators of the tools made changes to get around the changes made by Facebook - which in turn tweaked things again to shut down. and the cycle continued.
The upshot is that some tools are gone - probably permanently - and others work on and off. The links below are to the most consistent ones - with the proviso that they may or may not work at any given moment. It's good to be aware of more than one, and be prepared to try several.
* Sometimes, if a tool doesn't work when you enter the Facebook username, the user's unique ID number may get results
Allows searches for posts by keywords, within selected date ranges. From Henk van Ess and Daniel Endresz.
Finds a Facebook user's unique ID number.