Sometimes, these terms are used interchangeably, but there is a subtle difference. A software engineer is responsible for developing software from beginning to end in a systematic way, which may involve many steps. On the other hand, a software developer is responsible primarily for writing the code for software.
A software engineer has more responsibility than a software developer. To illustrate this, a software engineer has vast knowledge of all the processes involved in software development, from planning to deployment and managing stakeholders. In contrast, a software developer is mostly specialized in writing code for the software.