Vlogger PewDiePie is close to losing his crown as the most subscribed to YouTube channel as Indian channel T-Series catches up with him.
The two channels have been locked in a battle for days as the Swede fights to retain a title which he has claimed as his for around five years.
To millions, it is hugely important - so much so that one ardent PewDiePie fan hacked into 50,000 printers worldwide to spread the word about his channel and the race to keep him at the top.
Here's everything you need to know about the battle:
What are the two channels that are locked in a race to the top?
PewDiePie is a Swedish vlogger whose real name is Felix Kjellberg. He has held the crown of most subscribed-to channel for nearly five years.
He posts gaming videos, vlogs and general chat under the PewDiePie name, but has garnered controversy in the past over some of his content.
His battle against T-Series has been described as "David vs Goliath" since the Indian channel is the product of a company which posts Bollywood trailers and songs in a country of 1.3 billion people.
T-Series is a massive brand in India that has been running since the 1980s. "The problem for PewDiePie is that he simply can’t keep up with the machine that the T-Series YouTube channel," wrote Matt Binder on tech site Mashable. "The YouTube channel for the Bollywood music giant grows at close to 145,000 subscribers per day.
"T-Series, having started in the 1980s, is a legacy brand in India, a country with a population of 1.3 billion people.
"It has employees and an entire roster full of musical artists and Bollywood superstars that it relies on to pump out as many as half-a-dozen highly-produced music videos per day.
"In contrast, PewDiePie is just one guy putting out one vlog or video game stream per day."
How many subscribers have they got?
Both currently have over 73 million subscribers, but online tracking tool Social Blade documents that the gap between the two is closing to under 500,000.
The tool updates every second and is currently being streamed on YouTube, recording that T-Series racks up more than 150,000 new subscribers a day and PewDiePie just over 140,000.
What have they said about each other so far?
Following the printer hack, Kjellberg said in a video: "All of this support to keep me on top is so funny. I love it. Please keep it up.
"But don't do anything illegal OK... because that will look bad on me."
Kjellberg also posted a video on his channel asking supporters to fight on his behalf, and humorously challenged T-Series to a battle to the death.
DNA India reported last month that T-Series had hit back at Kjellberg for his goading, writing that the company is a "well respected platform".
President Neeraj Kalyan said: "It's a matter of pride for all Indians that an Indian YouTube Channel will soon be world's biggest channel on YouTube.
"But it seems a set of overzealous PewDiePie fans are negatively spamming T-Series channel on YouTube. I would like to inform them that we are not perturbed by this kind of behaviour.
"We will continue to build and grow our fan base globally. No amount of spamming will be able to hold back the power of good music."
