For performance reasons, django-simple-history always creates an HistoricalRecord when Model.save() is called regardless of data having actually changed. If you find yourself with a lot of history duplicates you can schedule the clean_duplicate_history command

$ python manage.py clean_duplicate_history --auto

You can use --auto to clean up duplicates for every model with HistoricalRecords or enumerate specific models as args. There is also -m/--minutes to specify how many minutes to go back in history while searching (default checks whole history), so you can schedule, for instance, an hourly cronjob such as

$ python manage.py clean_duplicate_history -m 60 --auto