In this paper several different digital soft clipping algorithms are described and analysed. It is discussed how the quality of each algorithm can be estimated. A testing methodology is devised to show the levels of nonlinearities produced as a function of the input signal amplitude. It is proposed that, while all soft clipping algorithms produce higher order nonlinearities, the instability of the produced harmonics plays a crucial role in the transparency of the effect. Existing and novel clipping algorithms are thus compared and classified based on their measured properties, including total harmonic distortion and inter-modulation distortion estimates. This paper proposes a conclusion related to the quality and properties of different algorithms.