The retroactive creation of new coins following a cryptocurrency’s launch, before public mining is possible.

What is post-mining?

Post-mining is a practice performed by developers that creates new coins following the launch of a cryptocurrency, but before public mining is possible. This allows the team to produce new coins without competition from external parties.
This sometimes occurs between the snapshot date — such as when token balances are counted so a newly created coin can be dropped or swapped on exchanges — but before code has been made public for outsiders to mine new coins.

Bitcoin Gold (BTG) conducted what many considered post-mining. The team behind the project produced 100,000 BTG between the snapshot date and the date that public mining began.

The founding team set aside 5,000 BTG for each of Bitcoin Gold’s six core members. The rest was left for growing the newly created currency’s ecosystem. But some saw these 100,000 BTG as a large amount for that purpose.

Coinbase did not support the launch of BTG, saying that the currency’s developers hadn’t made the code available to the public for review. The exchange considered this a “major security risk” — and a sense of negativity spread out across the community towards BTG.

BTG then suffered a 51% attack and, despite the team reacting and implementing an update to its mining algorithm, the damage had already been done.