Firefox Sync can share a variety of kinds of data between profiles, but cookies are not one of the kinds of data you can sync.

Ref. How do I choose what information to sync on Firefox?

Perhaps it is possible for an add-on to do it, but I'm not sure that would be secure.

Thanks for You answer

I'm sorry but to sync cooky is not my objective.

My objective is to understand   why i got from the same site different cookies if I use different profile.

 Let me add that if I copy cookies.sqlite from one profile to the other profile than the cooky for the site are identical.

But I don't understand why they where at the beginning ( when I access the first time the site ) different.

 I can imagine that something was set differently in an about:config item configuration  but it's very difficult  to compare the complete  about:config  belonging the the 2 profiles.

It's an interesting question. So for example: you start with no cookies for site A in either profile, visit site A performing the same actions in both profiles, and after your visits you have different cookies for site A in each profile.

You can use the Storage Inspector to view the cookies in a panel in the lower part of the tab: https://developer.mozilla.org/docs/Tools/Storage_Inspector

What kind of differences do you notice?

Firefox's cookie settings (in about:config, you can filter using cookie) can affect whether the cookie set has an expiration date in the future or is only a session cookie. Expiration is one of the columns you can display in the Storage Inspector's cookies list.

I report here the response and the request cookies for the 2 profiles:

I like to add that the related curl is OK for both profiles ( just is released a different structure of the output but still the output carry out all relevant information  !) . My investigation is just to understand why I got a different cookies behavior.

firefox profile num 1 =============================================

Response cookies { "__cfduid": { "domain": ".wigistream.to", "expires": "2021-04-26T17:04:14.000Z", "httpOnly": true, "path": "/", "samesite": "Lax", "value": "d84cc7cc0ff58a535ecd65223f1c412d11616864654" } } Request ccokies { "_ga": "GA1.2.972812746.1613419989", "passhash": "2d9535147b1a2c0567f109b0f4600a3adf144e4537a53835056f0fe97f115875", "uid": "3335" }

firefox profile num 2 =============================================

Response cookies { "__cfduid": { "domain": ".wigistream.to", "expires": "2021-04-26T17:07:56.000Z", "httpOnly": true, "path": "/", "samesite": "Lax", "value": "df9a17a74e1620f77d682c211699642a41616864876" } } Request cooky { "_ga": "GA1.2.489080285.1616752965", "hf1": "1" }

The "__cfduid" cookie looks like a session ID, so that needs to be unique for each browser. Actually, I found a post from Cloudflare saying they plan to stop setting this cookie, so it doesn't sound essential: https://blog.cloudflare.com/deprecating-cfduid-cookie/

The request cookies should be cookies that the site set previously and which Firefox is now returning.

"_ga" is an ID for Google Analytics.

I assume "passhash" and "uid" are present in profile 1 because you are logged in to that site?

I have no idea what the hf1 cookie is. It might be used to store a flag like "opted in" or "opted out" of cookies.

Your are rigth !!! I login to the site from the profile num 1  !!!. Just for testing Your excellent answer I login using profile num 2 and : voilà the respose cooky have "uid" and "passhas" !

My my biggest thanks