The settings are divided up into five different sections.

General

In the General tab you can set:

Default Days Till Candle: The number of days after start date to calculate candle date.
Default Days Before Hatch For Lockdown: Sets lockdown this number of days before hatch date.
(Android Only)Default Hour For Reminders: Allows you to specify the time of day for batch reminders. Use the 24 hour system i.e. 13 would be 1pm. Also the default settings in the built-in Android calendar will alert you an hour earlier. So in this case 13 would actually alert you at noon.
(Desktop Only)Show Splash At Startup: Toggles whither you see the splash screen when starting HatchKeeper.
(Desktop Only)Use Generic Notifications: Toggles whither HatchKeeper uses native or generic notifications. Under Linux and Windows it is highly recommended to use generic. Under Mac it's highly recommended to turn this off and use native notifications due to a wxWidgets/Mac bug that doesn't show generic notifications unless the main HatchKeeper window is visable
(Desktop Only)Open If Notification Clicked/Dismissed: On some platforms one works, on others the other one might, sometimes both might need to be enabled. Just try out several different configurations until it works.
Default Weight Unit: Allows you to set grams or ounces as the preferred weight unit. Note that this will only affect batches added after changing the setting and will not convert other batches.
Incubators: On the desktop click on the last entry(Add Incubator) in the Incubator list to add a new incubator. Click on any incubator to delete it. On Android just click the Edit Incubators button and make sure all incubators are seperated with commas, the first one will be the default. Do not put a comma after the last incubator.
Egg Tags: One the desktop just select the tag you want to edit from the list. Seperate all tag options with a comma, the first option will be used as a tag name. Do not put a comma after the last option. On Android it works exactly the same except you need to click a button instead of selecting a tag from the list.

Types

While HatchKeeper includes a nice selection of bird types and breeds by default, it is not practical to try to include every option out there. However since HatchKeeper was designed to be customizable, just switch to the Types panel in the settings and enter a new type name and the number of days it takes for that type to hatch and click Add Type.

Removing unused types is simple as well. On the desktop select a type and click Remove Type. On mobile, click on the icon beside the type name.

Breeds

You might need to add a bird type first. Adding and removing breeds is identical to types, except you select a bird type instead of incubation days. See the Types section for more.

GUI

This settings panel is only available on the desktop. You can change the text size for the calendar as well as colors used else where in the app. A complete restart is required for some changes to take effect.

DB/Database

This panel varies between the desktop and mobile versions. On the mobile version this panel combines the search engine with the database operation tools. Notes on the search engine for both mobile and desktop are found in the Searching section. The database tool are documented on the Database page.

Clear LocalStorage and Edit LocalStorage Value is only found on the mobile version. Clear LocalStorage will delete all localStorage values. This means some of your settings will be reset to default values. You can't undo this but no valuable data will be lost.

Edit LocalStorage Value allows you to edit any localStorage value manually. This is also for debugging and fixing problems.