Yohann Ramchelawon, who was jailed for 15 years, hid his identity behind a photograph of a teenage boy he grabbed from the internet.
The Mauritian national used Instagram, WhatsApp, Skype and Facebook to spark conversations with girls aged between 12 and 17 from across the world.
The 30-year-old sexually assaulted a six-year old schoolgirl and lured teenagers into sending him indecent images.
He was jailed at Stafford Crown Court on Monday after changing his plea midway through a trial.
Following his sentencing, children's charity NSPCC urged parents and carers to ensure their children knew how to stay safe online.
“This case is a stark reminder of the dangers young people face from predators on social media.
“It is vital that parents and carers talk to their children about staying safe online – whether it’s the importance of privacy settings, or the risks of sharing information with people you don’t know.
“It’s currently far too easy for adults to contact children online, so the NSPCC is calling on the Government to draw up a universal set of rules for all social networks - and to create an independent regulator with teeth to enforce those rules.”
Ramchelawon, who was on bail for similar offences at the time, was caught after West Midlands Police tracked the phone that he used to message a 12-year-old Manchester girl to a house in Walsall, where he was living at the time.
Detectives eventually caught him at a house in Victoria Lane, Huddersfield, where he was arrested on March 6.
Hundreds of indecent images were found on his digital devices as officers uncovered victims from Coventry and Walsall, plus Lanark in Scotland, Liverpool, St Ives, Shoreham-by-sea and East Ham, Stafford Crown Court heard.
Ramchelawon − who gave his home address as Walls Street, Halifax, when arrested − denied two counts of inciting a 12-year-old girl to engage in sex acts online, eight charges of possessing indecent images of children, and two of distributing the images.
He also denied another sex assault, and a sexual assault against a six-year-old Coventry girl in October last year.
But midway through his trial at Wolverhampton Crown Court he entered a guilty pleas to all offences.
He must serve at least 10 years behind bars before being allowed to apply for release and was also ordered to sign the sexual offenders register for life.
Online safety advice is available via the NSPCC and O2’s online safety helpline on 0808 8005002.