What PoW hashing algorithms did Monero historically use?

Question

Originally, Monero used the Cryptonight PoW algorithm, then started modifying it to thwart ASICs getting large parts of the network hash rate.

What is the timeline of these changes ?

Answer 1

Monero's genesis block dates back from april 2014. The first PoW change was in

The full history is:

| block   | date       | PoW algorithm
|---------|------------|--------------
| 0       | 2014-04-18 | Cryptonight (retroactively CNv0)
| 1546000 | 2018-04-06 | Cryptonight variant 1 (CNv1)
| 1685555 | 2018-10-18 | Cryptonight variant 2 (CNv2)
| 1788000 | 2019-03-09 | Cryptonight variant 4 (CNv4)

Monero is planning to switch to Random X, a new PoW algorithm not based on Cryptonight. This will likely be either near october 2019, or april 2020, depending on how well review goes.