After a policy that previously permitted them, Google has decided to remove any and all Chrome extensions that mine for cryptocurrencies after finding that too many developers didn't play by the company's rules.
Google allowed Chrome extensions that performed mining with the proviso that the extensions clearly disclosed that they performed mining and performed no activity but mining. About 10 percent of extensions that mined within the browser followed these rules, but some 90 percent didn't. Instead, they mined surreptitiously, driving up people's electricity bills and running down their batteries without any informed consent on the user's behalf.
In response to this continued misbehavior, Google has decided to ban any and all cryptomining extensions. Effective immediately, the Chrome Web Store will no longer accept any extensions that mine for cryptocurrencies and, starting in June, will remove any existing extensions that mine.