The National Archives of France is not the most advanced institution in terms of its digitized holdings, however, if you are researching French culture and history, you should be aware of it, and it may be helpful if your French ancestors were among the upper classes.
The Archives nationales (France) is making efforts to facilitate its online research process. You can find an introduction to the catalogue online in French, English and Spanish, and access it from there. For English, see http://www.archives-nationales.culture.gouv.fr/en/web/guest/salle-des-inventaires-virtuelle. Also go to http://www.archives-nationales.culture.gouv.fr/en_GB/web/guest/faire-une-recherche
Examples of the archives’ holdings include maps, photographs, documentation from the two world wars, and the records of Paris notaries. In addition, the archives has research centres focusing on topics such as place names and heraldry.
For many years, people with French Canadian or Acadian family lineages who wanted to know more about the research process in France have asked me whether the Archives nationales (France) in Paris was the place to conduct a family search. I have always replied that, if your ancestors in France were considered as nobility (familles nobles), yes, the Archives nationales de France is an online address you should consider. To check out the archives’ holdings on the ”bourgeois families” of France prior to the French Revolution, see https://www.siv.archives-nationales.culture.gouv.fr/siv/rechercheconsultation/consultation/pog/consultationPog.action?pogId=FRAN_POG_05&existpog=true&preview=false
However, if your ancestor was from the working class, you should conduct your online searches in the 95 Archives départementales de France. See my article https://genealogyensemble.com/2018/09/23/finding-ancestors-in-french-municipal-archives/
At the bottom of the following Archives nationales page, you will find links to a number of sites related to genealogy in France: http://www.archives-nationales.culture.gouv.fr/web/guest/signets-sciences
For many years the navigation process on the Archives nationales site was burdensome, and results posted from an online search would only indicate the dossier numbers (“fonds”) and a brief description of the fonds, followed by the ”série” (category of fonds) and the ”cote” (shelf number). If you one wanted additional information on the content of a dossier, you had to send an email to Paris.
As of September, 2018, even if you find your family name, in order to access the biographical material of that family, you must visit the Archives nationales (France) in Paris. To further complicate matters, the Archives nationales has more than one repository in Paris, and you must first determine in which repository the records you want to see are kept. You also need to determine the spelling of the family name in France at the time. For example, my name, Gagné, was spelled Gasnier.