You can now compare and view differences between two notebooks that are version controlled with Git in SageMaker. Jupyter notebooks (which SageMaker notebooks are built upon) are stored as JSON documents which include tags and metadata, making it difficult to diff with traditional line-by-line text diffing tools.  

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/10/sagemaker-notebooks-now-support-diffing/