Stars including Davina McCall have paid tribute to Ms Hartridge, who reportedly died in an electric scooter crash.
A statement posted on her Instagram account on Saturday confirmed her death.
The message to her 44,000 followers said: "Hi everyone. This is a horrible thing to have to say over Instagram but we know many of you were expecting to see Emily today and this is the only way to contact you all at once.
"Emily was involved in an accident yesterday and passed away.
"We all loved her to bits and she will never be forgotten.
"She has touched so many lives it's hard to imagine things without her. She was a very special person xxx."
In a comment below the statement, presenter Davina McCall wrote: "My heart goes out to Emily's family and friends. Such a shock. Sending you love and prayers."
Ms Hartridge, believed to be in her 30s, had more than 340,000 subscribers on her YouTube channel - which featured a weekly show about proving that "everything in the world can be explained with 10 reasons".
In the about section, she wrote: "The main purpose of my channel is to make you laugh and also throw in a bit of honesty because let's be honest (pun intended), life is JUST too short."
The Metropolitan Police would not confirm whether the woman who died after being struck by a lorry while riding an electric scooter on Friday morning was Ms Hartridge.
The victim, said to be in her 30s, was pronounced dead at the scene of that incident in Battersea, south-west London.
The crash happened at Queen's Circus roundabout shortly after 8.30am on Friday.
Several roads were closed while the scene was investigated, including Chelsea Bridge and Nine Elms Lane.
Scooters with electric motors are banned from public roads and pavements in the UK.
Electric scooters can exceed 30mph and are increasingly being used for short journeys in a number of countries, including in many European cities and the US.
Transport for London and Wandsworth Council redesigned Queen's Circus roundabout in 2015.
This trialled the use of raised kerbs and separate traffic lights to keep cyclists and vehicles segregated at junctions, but concerns were raised that the new layout was too complicated.
A cyclist was killed at the roundabout in July last year after being hit by a bin lorry.