They say imitation is the sincerest form of flattery, but in the super-competitive world of social media the copycats go for the kill.

In digital, where the cost of developing products of your own is increasingly weighed up against that of simply mimicking someone else’s successful idea, a war is being waged over selfie filters.

At stake is the future of Facebook and Instagram, and the growing monopolies they control.

Because to stay relevant beyond the generation of millennials that have hoisted them up among the world’s most lucrative and influential companies they are desperate for a younger demographic.

Pioneered by Snapchat, filters (quirky, fun graphics superimposed on photos and videos) are in mobile phone terms the addictive equivalent to young people of making slime, collecting Shopkins or worshipping unicorns.

Four years ago Mark Zuckerberg offered $3 billion for the company in an “if you can’t beat them, buy them” approach, but was turned down. Since then things have turned nasty.

Evan Spiegel’s Snapchat app facially maps features and dubs them with moving graphics such as rabbit ears or sunglasses. Music and other special ­effects add to the variety.

They have been an enormous success for the company, recently valued at $30 billion, as were their “Stories” posts that lasted for 24 hours.

All of these features have been unashamedly imitated by their rivals.

Facebook and Instagram (which Facebook owns) even took the same name “Stories” for their daily picture and video collections. And by doing so they’ve eaten into Snapchat’s value and arrested its progress.

Instagram’s copycat filter has been so successful it boasts 200 million daily users, more than Snapchat’s.

Those waking up to Instagram’s new filters yesterday could not have failed to notice some appeared to be virtual copies of Snapchat.

As intellectual property rights expert Kimberlee Weatherall, from Sydney Uni’s law department, says: “No one gets to own a good idea.”

She added: “When it comes to competing over a great business idea there is no IP, no trademark, no Passing Off law that applies.”

But Snapchat isn’t the only trendsetter and ideas leader in the sights of Facebook and Instagram.

The company’s live video streaming functionality has already driven the originator, Meerkat, out of the market and blown its key competitor, Twitter’s Periscope, out of the water.

Using their enormous global audiences, Facebook and Instagram are increasingly flexing their muscles to drive competitors out of business and to even influence the news cycle.

Jonathan Taplin, author of Move Fast and Break Things: How Facebook, Google and Amazon have ­Cornered Culture, said yesterday: “Data is king… and they are in control of it.”

(Originally published in The Daily Telegraph)