The French Ministry of Defense has created a section on the First World War at its portal Mémoire des hommes. On this website maintained by the Service historique de la Défense at Vincennes you can view the list with 1,3 million deceased French soldiers from the First World War (Mort pour la France). The 95,000 people killed in action without getting this mention, too, have been included in this database since November 2014. You can study unit diaries (journaux des marches et des opérations), check on members of the French air force, and look at the actions of individual units of the French armed forces. You can also study online the 107 volumes of the official history Armées Françaises dans la Grande Guerre (AFGG). There is a general search mode (Recherche globale) to combine these searches. The section Sépultures de guerre leads you to French war cemeteries worldwide. The website can be viewed in four languages (French, English, German and Spanish).
Among recent additions to the First World War section of Mémoire des hommes is a section on the Fusillés de la Première Guerre mondiale concerning executed soldiers and civilians, a resource presented also here.