Angela Lang/CNET

Samsung's trying to make it easier to use its smartphones by redesigning the software running on them.

The company on Wednesday unveiled its new One UI user interface. It will roll the software out to the Galaxy S9, S9 Plus and Note 9 in January -- and the interface will be on the upcoming foldable phone that Samsung showed for the first time Wednesday. Samsung is first making One UI available to people in the US, Germany and South Korea for beta testing next week.

"With One UI, users only see what they need when they need it so they can stay focused on what matters," Jee Won Lee, Samsung senior designer of UX design, said Wednesday during a presentation at Samsung's developer conference in San Francisco.

While Samsung uses Google's Android to power its phones, it builds an interface that sits on top of Android. The software, previously called TouchWiz and then renamed Samsung Experience, was heavily criticized by reviewers in its early days, but it's evolved dramatically over the years. One UI goes even further in its efforts to make interacting with Samsung devices more seamless. The goal is to make interactions more natural, like for one-handed user operation.

The minimal interface was designed to reduce clutter and distractions. Samsung also sought to increase visual comfort, making it easier to stare at the screen for longer. One UI splits the screen, keeping the most relevant content at the bottom half of the screen to make it easier to use with one hand. The notifications are still at the top of the display, though, so you can't ignore that area entirely. Rounded corners of the interface echo the rounded corners of Samsung's devices.

It also regrouped functions so the ones used most often come first. Necessary buttons are there when you need them and go away when you don't. For instance, the search bar and menu tabs disappear when you make a call.

As phones keep getting bigger, it's harder to use them the same as in the past. Most people can't easily reach the top corner of a display using only one hand, for instance, and people are doing even more things with their devices. Because of that, Samsung's tweaked its user interface to work with these newer displays, including its upcoming foldable phone that will mark a huge change in device design.

Now playing: Watch this: Samsung's foldable phone will use One UI

"We're using gigantic phones now, but our hands haven't gotten any bigger," GlobalData analyst Avi Greengart said. "Displays have gotten longer and having things out of reach makes the phones hard to use. Samsung is trying to address that in software."

Wooing developers

The annual Samsung Developer Conference started off small in 2013 at a San Francisco hotel. In 2016, it expanded to Moscone Center West, where Apple previously held its developer conference. Last year, 5,000 people attended SDC.

Angela Lang/CNET

Samsung has been building its capabilities in software and services over the past decade, but it's had more flops than successes. It's launched services -- including Bixby's predecessor, S Voice -- only to scrap them a few months or years later. Instead of using its homegrown Tizen operating system in its high-end smartphones, Samsung has relegated the software to wearables and other products and continues to rely on Google's Android software to power its smartphones and tablets.

SDC reflects Samsung's big push to get developers to make software specifically for its devices. In the past, that's meant making apps that work on the edge of Samsung's curved smartphone displays or take advantage of its S Pen stylus. This year, that focus has turned to Bixby and artificial intelligence.

Earlier Wednesday, Samsung said it plans to move its Bixby voice assistant to more products beyond mobile devices, open the software up to developers and make it work with five more languages, in an effort to help its AI gain traction with users.

Samsung also showed off its upcoming foldable phone for the first time. The device, which will be mass produced "in the coming months," is a tablet when it's fully opened and then a phone when it's closed. It uses a new display technology called "Infinity Flex Display" that lets you open and close the device over and over without any degradation.

First published at 11:18 a.m. PT

Update at 12:05 p.m. PT: Adds more details.

5G is your next big upgrade: Everything you need to know about the 5G revolution.

Taking It to Extremes: Mix insane situations -- erupting volcanoes, nuclear meltdowns, 30-foot waves -- with everyday tech. Here's what happens.