It is normal to have a few drops of moisture in your jars, especially if you live in warmer/humid climates closer to sea level. The tops of your jars that do not contain liquid, do contain air when the jar is sealed. That air has no place to go.
Condensation happens when warm, moist air is cooled. The cooling air doesn’t have the same capacity for water vapor as the warm air, so the water transforms back into its liquid state. It is not a sign that your extract is bad. Typically, the condensation will eventually reintegrate into the extract. Remember, if you used 35% alcohol, the remaining 65% is water, so as the condensation settles back into the extract, you will be fine.
You may see this often if your jars are stored in a place near a furnace, or oven, or fireplace, etc. Any time the liquid is heated and then cooled, condensation will reappear. Storing them in a cool dark place with minimal temperature fluctuations is always best.
Visit our vanilla extract making guide center for more tips and tricks to making vanilla extract.