Disclosure: I build Schemity, a desktop ERD tool - this post is from our blog and uses it for the examples.
TL;DR: ChartDB is the strongest cloud schema visualizer, but the cloud is the product. Schemity is the offline desktop alternative: local JSON storage, Git-native versioning, BYOK AI, and reviewed migrations - for when the diagram can't leave your machine.
ChartDB nailed something real - run a query, get a diagram, share a link, with an AI assistant on top - and Schemity is its offline desktop counterpart: a ChartDB alternative that keeps diagrams as local JSON files, runs AI on your own key (BYOK), and costs $129 once instead of a subscription. The difference is not polish. It is where your schema physically goes.
That difference bites when a certain kind of engineer hits a certain kind of wall: the schema you want to diagram is the one you are not allowed to upload. The client's NDA, the IT policy, the compliance checklist - somewhere in there is a sentence that ends the conversation with any browser tool: project data does not go to third-party servers. This article is for the engineers who love what ChartDB does and cannot use it where it does it.
The Honest Summary
