It happened to bitcoin last year and this rare network occurrence can hit its alternative currencies.

The fourth most valuable cryptocurrency Dogecoin “forked” Monday — meaning that the virtual currency’s blockchain has split into two competing chains.

Alert Redditors quickly posted updates and guidance for dogecoin miners, apparently isolating one of the chains as the one most likely to remain intact.

Cryptocurrencies use a single “chain” — or blockchain — of transactions to achieve consensus and to solve the double-spending issues.

It appears the blockchain from clients “version 1.5+” won’t be orphaned. What does that mean for the chain put out by older client “version ~1.4”?

Since there are two chains, a user on the wrong “fork” could perceive a transaction as completed, when it is actually not completed.

This is not the dreaded “51% attack” — which could theoretically threaten network security of the particular altcoin affected.

The network will survive the fork, as did bitcoin about a year ago.

As usual, the dogecoin subReddit is guiding miners and other dogecoiners on the issue.