This is a Open in Browser icon. We've made it in iOS style, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 12,300 icons, all in the same style and quality.
This is a picture of a browser window. It's blank for the most part, and on top has a bar with two black circles and a rectangular bar on the right side of that. There is a large curved arrow pointing into the box, pointing upwards.