The historical data files are downloaded as compressed .tar files and can be opened using zip utility such as WinZip / 7zip.
Assuming you've downloaded 7zip and are using Windows, please go to
- Start> Computer > Downloads
- Select the downloaded file
- Right click > Select 7 zip > Open archive
- Access the file directory and select one of the files
- Select the file you'd like to open
- Right click & select 'Open With'
- Select 'Notepad'
The data will then be available in Notepad in .json format. You can then use other tools to view the data in the format of your choice.
There is Python and Excel sample code available here
This includes an Excel Historical Data Workbook sample for customers who want to view/use their purchased BASIC data within Excel.