Flag expertRoman Mars declared it during a TED Talk in 2015 to be the most "badass" city flag in the world, as well as an example to others. He particularly praised the simplicity and popular appeal that led to its widespread use.
The colors of the flag are derived primarily from the coat of arms of the city of Amsterdam, or rather from the shield in it. Their meaning is unclear. According to the city government, its origin could go back to the coat of arms of the Persijn family, which once owned a large tract of land in the capital. These colors as well as the crosses are to be seen in the flags of both Ouder-Amstel and Amstelveen.
The popular legend that the three Saint Andrew's crosses were meant to ward off fire, floods and the black plague is unfounded as the use of three St. Andrews crosses by noble families in the area precedes the arrival of the Black Death in Europe.
In the coats of arms of two other Dutch cities, Dordrecht and Delft, the middle stripe symbolises water. In regards to Amsterdam, this black strip becomes the River Amstel.