Double spending are in fact bitcoins that are spent twice or more by their holders, and on the Bitcoin blockchain they are virtually impossible.
Should there be a way to spend the same BTC twice, it could be said that the Bitcoin blockchain has been hacked, and would no longer function properly.
Therefore to say that there has been double spending on Bitcoin’s blockchain is tantamount to saying that it is not working properly, and should the process that would have allowed the double spending even be replicable, it would mean the ultimate end of Bitcoin.
In light of this, it’s all too obvious how serious it is to accuse Bitcoin’s blockchain of suffering from this problem, so statements of this kind should be beyond measured and verified before being released to the masses.
So instead, it didn’t happen, and false reports of double spending were spread that never actually happened.
Double spending on Bitcoin: what really happened
One of the world’s top Bitcoin experts, Andreas Antonopoulos, explained what happened.
Antonopoulos has published a long thread on Twitter, with 24 tweets, in which he explains that what really happened is in fact simply a normal re-organization of the chain that occurs whenever two different versions of the same block are mined more or less simultaneously.
In these cases, in technical jargon, it is said that a stale-block has been mined, which can generate a momentary double expense that is automatically rejected by the system in the following blocks, as already described some time ago in a Cryptonomist article.
Since these events are rare but not very rare, so much so that Antonopoulos himself reveals that a re-organization of 1 block happens on average every two weeks, Bitcoin users should be aware of this. And since the solution is very trivial, the problem is of such simple solutions that it cannot cause any concern.
In fact, it is enough not to limit oneself to waiting for a single confirmation block for transactions, but to wait for at least 3 or 4, so as to give the blockchain time in cases like these to reorganize itself automatically, eliminating any double spending.
Those who decide to limit themselves to waiting for a single confirmation do so at their own risk.
Until today, in over 12 years of almost perfect functioning, stale blocks have never caused major problems. Therefore spreading a news that hypothesizes a serious malfunction, confusing a normal process of reorganization with a bug of the system, is at least very reckless.
Finally, it should be added that users who do not want to wait for more confirmations for the validation of their transactions can use Lightning Network, which allows immediate transactions without any risk related to stale blocks.