The Worldwide Developers Conference 2019, arguably one of Apple's (AAPL) most important events of the year, kicks off on Monday. Held at the San Jose Convention Center, WWDC is traditionally where Apple announces all of the latest updates coming to its various operating systems including iOS and macOS.

There's talk of changes coming to the ever-popular Messages app, improved multitasking, cross-platform apps from iOS to macOS and an app store for the Apple Watch. It'll be a huge show, with a ton of news.

These are the biggest updates we're expecting from WWDC 2019.

iOS 13

Apple's iOS is one of the most popular operating systems in the world. It powers more than 1 billion devices used by consumers from America to Zimbabwe, making any changes to the operating system incredibly important for Apple.

For 2019, the company is expected to roll out its iOS 13 update with key enhancements coming across the board.

According to Bloomberg's Mark German, Dark Mode will be accessible via Control Center and darken the screen to help conserve battery life as well as give your eyes a break from looking at bright colors all day. Apple's macOS already has a dark mode for desktop and laptop computers, and it does make staring at a screen all day a little easier on the eyes.

Apple's Message texting app is also getting a few tweaks. Specifically, Apple is reportedly adding the ability to create your own username and profile picture for Messages. Doing so will make the app feel more like third-party messaging apps like WhatsApp, Facebook's Messenger and Signal. There should also be more animoji fun, considering the invitation for WWDC prominently features Apple's AR-powered emojis.

According to 9to5Mac, the iPad could also be getting improved multitasking including the ability to use a single app in two separate windows. There are also rumors that the iPad could get mouse support, according to MacStories editor-in-chief Federico Viticci. Both of these updates would help move the iPad into a better position to serve as a true laptop replacement device.

Bloomberg also reports that iOS 13 will get a revamped Health app that will provide users with a better overall understanding of their health, including menstrual cycle tracking functionality. Other companies offer a similar feature, but this would be the first time Apple would add it to its Health app.

macOS

Apple's macOS is the operating system that powers the company's MacBook laptops and Mac desktops. For 2019, Apple is reportedly looking to increase its cross-platform compatibility for iOS apps.