Home Canning Broth - Reducing Volume By Half First
If the broth is beef or chicken based you need to follow the USDA research-based recipes. Pints are processed at 11 pounds (Dial gauge), and 10 pounds weighted gauge for 20 minutes. Quarts processed for 25 minutes. This is provided there are no vegetables or meat.
You can down load the recipes from https://nchfp.uga.edu/how/can_05/stock_broth.html