Online worker usually appears on homepage at poolin.com, which refers to the total number of online workers of a certain currency in the mining pool.
Status of active worker, inactive worker and dead worker can be view through your sub-account.
Active worker: the worker connects to mining pool normally under current sub-account.
Inactive worker: the worker disconnects to mining pool no more than 1 day (15mins＜disconnection＜24 hours) under current sub-account.
Dead worker: the worker disconnects to mining pool more than 1 day (disconnection＞24 hours).