Louis Tomlinson

Louis Tomlinson

Vivian Zink/NBC/NBCU Photo Bank via Getty Images

The Billboard Social 50 dated Dec. 31 is chock full of members of One Direction and Fifth Harmony -- newly solo and otherwise -- led by One Direction’s Louis Tomlinson, who debuts at No. 3 after the release of his new single, “Just Hold On,” with Steve Aoki.

The Social 50 is powered by data tracked by music analytics company Next Big Sound, and ranks the most popular artists on Facebook, Twitter, Instagram, YouTube, Wikipedia, Tumblr and Vine. The chart's methodology blends weekly additions of friends/fans/followers along with artist page views and engagement. The latest chart reflects the tracking week ending Dec. 18.

Tomlinson starts at No. 3 on the chart following the debut of “Just Hold On,” his first single outside of his work with One Direction, with hungry fans eager to chat about the new material. On Twitter and Instagram, the boybander received 1.4 million and 988,000 mentions, respectively, in the tracking week according to Next Big Sound.

Tomlinson’s debut ties for second best among starts of One Direction members past and present on the chart; while Liam Payne entered at No. 17 (Nov. 12-dated chart), Zayn also started at No. 3 (Feb. 13), while Niall Horan debuted at No. 1 (Oct. 15). The lone member of One Direction that hasn’t charted is Harry Styles, who has yet to release – or even tease, in Payne’s case – solo material.

Concurrently, Tomlinson debuts on the Billboard Hot 100, with “Just Hold On” debuting at No. 52. The track also starts at No. 1 on Dance/Electronic Digital Song Sales and at No. 6 on the overall Digital Song Sales chart, selling 54,000 downloads in the week ending Dec. 15, according to Nielsen Music. Meanwhile, Aoki, who celebrates his best position on the Hot 100 with the track, enters the Social 50 for the first time, debuting at No. 13.

But Tomlinson is far from the only pop group member to go solo and climb the Social 50. Here’s a quick rundown of other group members (again, past and present) and their ranks this week.

-Niall Horan: No. 5, Social 50. After leading the Social 50 for two weeks earlier this year, One Direction’s Horan leaps 19-5 with a particularly big week on Instagram, garnering 6.4 million reactions (up 119 percent). The leap comes as Horan posted pictures documenting his performance of “This Town” on The Tonight Show, plus his spot on iHeartRadio’s Jingle Ball tour. Concurrently, the song climbs into the top 20 of Adult Pop Songs, rising 21-17.

-Camila Cabello: No. 10. Nothing major for the newly departed member of Fifth Harmony just yet – wait until next week’s Social 50 for more on that (as the latest chart’s tracking week closed on Sunday night, just as news broke of her departure from the group) -- but Cabello does climb back into the Social 50’s top 10 (11-10), with her biggest gain being in Twitter followers (24,000 new accounts, up 65 percent). “Bad Things,” her collaboration with Machine Gun Kelly, continues its ascent on the pop charts, moving into the top 10 on Pop Songs (13-9) with a 19 percent leap in airplay. As for her former group Fifth Harmony, they climb 26-22 on the latest Social 50.

-Lauren Jauregui: No. 14. After debuting on the Social 50 at No. 17 a week ago, Fifth Harmony’s Jauregui reaches No. 14, following continued buzz surrounding her first solo single, “Back to Me,” with Marian Hill. The song rises to a new peak of No. 4 on the Billboard & Twitter Top Tracks chart, and also sells 9,000 downloads.

-Zayn: No. 19. Former One Direction member Zayn rockets back onto the Social 50, re-entering at No. 19 with gains in almost all social metrics, chief among them a 1,035 percent boost in Instagram reactions to 2.5 million total. Releasing a new song with Taylor Swift -- “I Don’t Wanna Live Forever” -- will do that for you, as the song premieres at No. 6 on the Hot 100 and No. 1 on Digital Song Sales (188,000 downloads).

-Normani Kordei: No. 24. Louis Tomlinson isn’t the only pop group member who debuts this week on the Social 50. Fifth Harmony’s Kordei starts at No. 24 after releasing solo material on YouTube: a mashup cover of Drake’s “Fake Love” and “Sneakin’.” Of her overall chart points, 60 percent come from mentions on social media -- unsurprising, given her multiple posts and retweets about her new song.

-Liam Payne: No. 46. The One Directioner -- who is still working on the official release of his solo material -- re-enters at No. 46 with a gain of 113 percent in Twitter followers (adding 80,000). He also leaps 24 percent in Instagram reactions to 1.1 million, with one of the more circulated posts being his condolences to bandmate Tomlinson, whose mother died Dec. 7.