Objectives: . This study evaluated the electroacoustic characteristics of smartphone-based hearing aid applications (apps). Methods: . We investigated hearing aid apps based on processing delay measurements, hearing instrument testing, simulated real ear measurements, and a head-and-torso simulator. Results: . Many apps exceeded the recommended level for processing delay. Hearing instrument testing showed the highest amplification characteristics and the best sound quality when a hearing aid was used, followed by the high-end apps and then the low-end apps. The simulated real ear measurements results showed that the high-end apps had a better ability to match the amplification targets than the low-end apps, but there was no consistent pattern among apps when controlling the output. Only a few apps could improve the signal-to-noise ratio in the head-and-torso simulator. Conclusion . Most of the apps showed relatively poor electroacoustic performance in comparison with hearing aids. Generalizing access to hearing care through hearing aid apps induces a wide diversity of hearing performance with no fixed standard for reliability. However, we expect their overall quality to improve over the next few years.