Apple's App Store has 1.4 million titles (as of June 2015), so there are more apps than anyone can try in a lifetime. We've tested hundreds this year alone, and only half were worthy of coverage and far fewer earned our praise. But the greatest compliment we can pay an app is putting it in heavy rotation on our phones. Here are the iOS apps that my colleague Tuong Nguyen and I just couldn't quit using this year.

Layout from Instagram

iglayoutscreen.png

I enjoyed collaging on poster board as a kid but never as an adult on my iPhone. Layout from Instagram changed all that. Select up to nine photos, and Layout instantly displays how they'll look in seven unique collage types, so there's no guessing. Choose your preferred collage, and from there you can easily reorder photos via drag and drop, pinch to zoom in, or adjust photo sizes with sliding gestures. You can also flip and rotate photos to create visually arresting effects. Then save or share over social media directly from the app.

Boomerang from Instagram

igboom2.png

Apple's Live Photos launched earlier this year, but it was impossible to see these living images on any social media sites for months -- that is, until Tumblr and Facebook began supporting them. That's why Boomerang from Instagram, which was always supported across social media sites, is such a boon. Just point your iPhone's camera at a moving person, animal, or object and press the capture button. Boomerang takes a burst of photos and connects them in a mini video that keeps replaying. What's more, because you're left with a video file instead of a Live Photo file, you can share it across all your social media.

Imgur

imgcreen.png

Initially launched as an image-hosting site for Reddit users, Imgur has spun off into its own dedicated community of "imgurians" excited to check out new images. There have been 900 billion image views in 2015 alone. Anyone familiar with Reddit will get the process. Users can share any images or GIFs as long as they don't violate the site's terms. Images are then upvoted by the community, and the most popular get promoted from the homepage. Posts can range from wacky to more serious. The site has become a launchpad for both many of 2015's popular Internet memes as well as for what's culturally important today. With the release of Imgur's mobile app, users can now post, check out, and upvote photos whenever they have a few minutes to spare.

Robinhood

robinhoodscreen.png

With a slick, intuitive UI, quick setup, and no-cost trading, Robinhood makes it easy for new investors to start trading. We've found that the best way to use the app is as a learning platform. Newly released cards and insight features bring you up-to-date news related to companies in your portfolio. Partnerships with Openfolio, Quantopian, and Stockwits allow you to compare your portfolio, manage trades, and buy shares through third-party apps.

Check out Apple's picks for the Best Apps of 2015.

Tuong Nguyen also contributed to this article.

Joshua Rotter is a copy editor for Download.com and covers iOS.