Ibrahim Roger Anderson, 44, pledged support for the terrorist group unaware the woman he was speaking to on Facebook and Telegram was a covert officer.
Anderson, a car mechanic of Luton in Bedfordshire was handed a seven-year jail sentence at the Old Bailey on Wednesday after admitting a string of terror offences.
He had previously been jailed for three years in 2016 after being convicted of trying to drum up support for Islamic State outside Topshop in London’s Oxford Street.
Sentencing judge Philip Katz QC said of the footage Anderson shared: “Some of it is at the worst end of the range seen in this court.”
Prosecutor Julia Faure Walker said Anderson shared videos with the undercover officer which depicted “extremely graphic” footage of Islamic State executions, suicide bombings, and glorification of past battles.
The propaganda – with titles including “Flames Of War”, “Answer The Call”, and “Procession Of Light” – also featured a father encouraging his children to follow him into martyrdom.
In one message to the undercover officer, Anderson, a father himself, said: “We will, with the help of Tawhid (the belief in the oneness of God), raise the black flag over London.”
Anderson pleaded guilty to 10 counts of disseminating terrorist publications, and four charges of possession of terrorist publications relating to Islamic State, and was told he would serve two-thirds of his sentence before being eligible for parole.
He also admitted breaching his terror notification requirements when he withheld an email address from the police in an attempt to prevent the police from linking him with the Facebook account, receiving an additional 12-month jail term.
Patrick Harte, defending, said his client was “contrite”, more open-minded about other religions, and expressed his remorse.
But he said he “turned to the internet for some sort of release” during the coronavirus pandemic, when he spoke with the undercover officer.
The judge added: “Like so many others, you were spending too much time in the dark regions of the internet.”