I've heard that Papyrus is pretty good

I like Source Sans Pro. https://www.google.com/fonts/specimen/Source+Sans+Pro

Pros

• 12 styles
• Low contrast + tall x-height = good readability at small sizes
• Freely available

Cons

• Fairly common on the web. If you're looking to differentiate yourself, might try something else.

Roboto was created for android UI, so it's pretty good. I like a lot Fira Sans, created by Erik Spiekermann. As it's created by a typo master it's very legible and can be used at small sizes. Also Fira Sans is quite narrow: you save space.

Other interesting fonts: Droid, open Sans

http://somadesign.ca/demos/better-google-fonts/

Have your pick from here

I really like Gudea lately. Works great at a small size w/ numbers and a "skinny" font (not wide).

The only weakness to me is lack of different weight (only normal, bold, and Italic).

Oh, and a Google (read: free) Web font.

Good article from Typecast on a few choices (most of which have been suggested): http://typecast.com/blog/type-on-screen-5-faces-for-ui-design. Breaks down why he made these suggestions.

Proxima Nova is all the rage at the moment.

Whitney

Avenir, Proxima Nova and Open Sans.

Open Sans FTW

Avenir

Hi, can anyone identify the typeface used in the Conflux screanshot here: https://cnflx.io/ It seems to be incredibly legible and clean, and looks kinda like a subtle modified version of Proxima Nova...

At YouTube we still use Arial - but Google in general is moving to Roboto (the font used on Android). https://www.google.com/fonts/specimen/Roboto which was Open Sans before.

I tend to follow these rules:

iOS = Helvetica

Android = Roboto

Windows apps = Segoe UI

Mac apps = Lucida Grande

Web/other = Look at your brand, and find a compatible, readable font with light/regular/bold weights, such as Open Sans and Source Sans.

As shown in the button test, your UI is part of your brand, so in environments where there is no set typographic guidelines, you should consider communicating your brand through your UI typography.

I'm a fan of Freight Sans Pro, myself.

You can check this list out as well.

http://www.webdesignerdepot.com/2014/02/improve-your-coding-with-25-hyper-legible-fonts-for-programmers/

LOBSTER ALL THE THINGS....

I like OpenSans. It's very clean, simple and readable.