The massive queue formed in the Tesco in Duke Street this afternoon, with many children arriving to wait their turn after school.
The coffee chain is celebrating by treating its customers to a drink on them, while aiming to change the public's perception of coffee making machines.
One man who was in the Tesco store at the time said: "It was carnage. The kids were just arriving from school. There were around 50 people waiting when I passed.
"They all queued up nicely and were waiting their turns but getting to the shelves behind them was a bit of a nightmare.
"As I was leaving more groups of kids in uniforms were jointing the queue."
Dozens of machines across Edinburgh are being used by the public today for their free coffees.