Online voltage stability analysis is one of the essential element for the robust operation of the power systems. Voltage stability limit is described by the margin of the current operating point to the voltage collapse or saddle-node bifurcation point where the real solution to power flow equations disappears. Whereas the online analysis is required for updating the distance to voltage collapse point in real time as the state of the system changes due to some disturbance or contingencies and has a constraint on computational time. In this manuscript, we propose a computationally efficient algorithm for online voltage stability analysis to update the margin to voltage collapse in real time by using the information from the base case collapse point and in time measurements. The proposed algorithm is based on the Newton-Corrector approach in which the system of power flow equations is solved with an additional parametrization equation. Implementation of the algorithm is described in details, and its performance is validated on several IEEE cases.