This week in social media, Facebook adjusted the algorithm for your News Feed again, while again being declared the number one app on Android and iOS smartphones. Meanwhile, Twitter tested a GIF button for its mobile app and made its website easier to use, and Snapchat ran its first mobile app-install ad.

It's time for Social Media Sunday!

Facebook

Changing the News Feed, Again

Facebook is adjusting what shows up in your News Feed, yet again. This week, the company announced it was changing the News Feed algorithm so that users' News Feeds show fewer posts that aren't likely to get attention at the top. According to Forbes, Facebook said it had surveyed over 1,000 users about the News Feed, asking them to rate their experience with the feature on a daily basis.

Users ranked each post on a scale of one to five, based on how much they wanted to see that post on their News Feed. Facebook found that user experience climbed when the posts they were most likely to rate highly, and click on and engage with (like, share, or comment) showed up at the top of the feed.

Based on that, Facebook will be adjusting News Feeds from now on based on both the personalized metrics that come from user actions -- liking, sharing, clicking or commenting on a post -- plus the rank Facebook gives posts that determines the position of stories in the New Feed. Users can still use the "See First" feature to manually override any changes the new algorithm might make, and can always make further adjustments in preferences.

Facebook App Dominated Mobile in 2015 - Report

Analytics company ComScore released a report this week ranking the top 15 smartphone apps in 2015 in usage across both Android and iOS smartphones. Facebook took the top position, with a reach of 76.8 percent, according to BGR. Right behind, at second place was Facebook's own Messenger app, which resides on 62.5 percent of all smartphones.

Meanwhile Instagram caught ninth place, with a reach just under 40 percent, while Google apps like Search, Maps, and Gmail (emphatically not including Google+) grabbed five of the top 10 most popular apps in the world.

Speaking of Gmail, according to Mashable, the over-a-decade-old Gmail reached more than 1 billion monthly active users this week. Facebook's WhatsApp messaging service, which was launched five years after, also claimed the same milestone minutes after Google's announcement.

Twitter

Tracking Conversations on the Web

Twitter just fixed a problem users and lurkers run into when they try to follow a long conversation from the web. It's a simple change, but effective. Now clicking on a tweet will open a separate window in your timeline, along with the replies for tweets that have garnered a lot of engagement, all listed in the form of a conversation.

It used to be that once you expanded a conversation, not all replies would appear in relation to the original tweet, and users frequently got lost in the conversation if they tried to follow up on multiple replies. According to Mashable, the change has gone into effect for the web, but there's no word yet whether changes will be coming to the mobile app, as well.

Mobile GIF Button On the Way?

It seemed like forever before Twitter introduced GIFs to its platform in a way that didn't frustratingly limit users to pre-approved images.

Now, it seems Twitter is testing a stand-alone button for its mobile app dedicated to posting GIFs, as TheVerge reported number of users finding an option simply labeled "GIF" next to the photos button in the app's screen for composing tweets.

Twitter didn't comment officially on the new feature, but the button brings up a number of ready-made GIFs to post, possibly including some from the image catalogues of third-party image-makers.

Snapchat

Testing App-Install Advertising

Snapchat continues to expand its experimentation with advertising options, according to AdWeek, displaying its first mobile app-install advertisement this week.

The promotion was for Cookie Jam, and included a 30-second video commercial within iHeartRadio's Discover channel, followed by instructions to swipe up to download the game directly from the App Store without leaving the ephemeral messaging app.

Previously, Snapchat has explored media content partnerships with its Discover section, along with sponsored "Lenses," which offer users branded ways to add graphic layers over their snaps.