PARIS — It is a mind-numbing 3,324 pages long and growing. Of those, 170 pages govern firings, 420 regulate health and security, 50 temporary work and 85 collective negotiations. Hundreds more are devoted to wages, specific industries and overseas departments.

It is France’s infamous, almost indecipherable labor code, the Code du Travail, both revered and reviled. Unions hold its protections sacred. Employers blame it for making it expensive to hire new workers and difficult — and even more costly — to fire them.

France’s energetic young president, Emmanuel Macron, has made lightening the code — a touchstone of French economic life for over a century — the centerpiece of his promise to revitalize the economy. He wants to have his changes in place by September.

A former investment banker sympathetic to business, Mr. Macron is aiming for nothing less than to remake French capitalism. His success or failure may be the single most important test of his mission to renew France.