I appreciate the ‘different browsers use different extensions’ point you make. I guess I was thinking more along the lines of whether the Flash Player extensions all shared the same local object settings. While this can be the case in a win-IE-FireFox setting (for example), from you comments I take it that cannot necessarily be extrapolated across all OS, browser, Flash Player configurations?

To tell you the truth I’m not sure where the 4KB originally got stuck in my mind. Google turned up this older article on shared objects in Flash MX which seems to imply it:
http://uk.builder.com/webdevelopment/design/0,39026630,20278036,00.htm

A.

Depends ont he browser. IE/Win uses system-level ActiveX Controls, and so any variant browser (NeoPlanet, eg) will use the same system-level extension.

Modern Macintosh operating systems also use system-level browser extensions, but I’m not sure which browsers use these shared resources and which use the traditional local “plugins” folder.

(Rephrased, some browsers share extensions, and some do not, and I don’t know that anyone has collected together the documentation for each browser version on this characteristic.)

I’m not sure where the “4 KB” figure came from… maybe this is “What constraints do various browser have on cookie size?” If so, then this is another cross-browser feature which I haven’t seen documented (across brands) before.

“Are the browser cookie file format(s) published? How about Flash Player local objects?”

These are the same thing, though…?

I don’t think the local storage format has ever formally been written up, because this isn’t intended as a data-exchange format. A few years ago these were stored in domain-specific directories, in plaintext name/value pairs, but the ability to write arbitrary strings to a predictable disk directory address could conceivably have been used to nefarious effect, and so the data and filenames were hashed up a few years ago, and are not as human-readable as before.

jd/mm