At the moment, SmartCite is supported in Word 2016 and above, Office 365 and Word Online.
SmartCite Add-in is also available for Google Docs.
If you don't have a subscription for MS Word you can use SmartCite for Citekeys across a variety of tool:
- Microsoft Word
- Google Docs
- Manuscripts App
- Scriveners (Coming Soon)
- Ulysses (Coming Soon)