From Worsley in Manchester, the teenager has now been named as David Celino.
David was taken to hospital on Saturday night and passed away in the early hours of Sunday morning (28 August).
In a tribute, his family said: “Our David was a beautiful, fiercely independent and warm character who lived every day at 110 percent and who loved to spend time enjoying music with his friends.
“He had just received fabulous GCSE results, got into college, and had hoped to study computer science at a top university.
“Leeds Festival was the highlight of his summer; ultimately it was to take his life in the most unfair, cruel and horrible way, and we are broken.”
Police enquiries into David’s death remain ongoing.
Assistant Chief Constable Catherine Hankinson of West Yorkshire Police, said: “Our thoughts are with the family of the boy who has died, and we have officers supporting them at this very difficult time.
“While the exact cause of his death is yet to be established, one line of enquiry is that he had taken a particular type of ecstasy (MDMA) tablet, which was described as a grey or black oblong shape.
“At this moment in time this is believed to be an isolated incident as we have not received any similar reports.
“Users of any drug which is not professionally prescribed can never be sure of their contents and the risks involved with taking the substance.
“Anyone who does feel ill after taking any substance should seek urgent medical attention.
“We are continuing to conduct enquiries on site and are liaising closely with the event organisers.”
The festival organisers say they are 'working closely' with police and 'take all reports of incidents where drug use is suspected seriously'.
Melvin Benn, managing director of Festival Republic, said: “We are truly saddened about this tragedy and our sincerest thoughts are with the family at this time.
“We are working closely with West Yorkshire Police to assist with their investigation and take all reports of incidents where drug use is suspected seriously.
“The safety and wellbeing of all our festival goers is always our absolute priority and we remind all festival goers that there is no safe way to take prohibited drugs and there are no safe prohibited drugs.”
Anyone with information is asked to contact police or security on site, call 101, or visit the West Yorkshire Police website.
If you have experienced a bereavement and would like to speak with someone in confidence, contact Cruse Bereavement Care via their national helpline on 0808 808 1677