ToolJet

ToolJet builds internal apps from a widget library, tables, forms, buttons, charts, wired to queries against Postgres, MongoDB, Airtable, and a long list of REST and GraphQL sources, with JavaScript transformers available for shaping data mid-query. Multiplayer editing lets more than one builder work on the same app at once, which matters once an internal tools team grows past one person.

The self-hosted, open-source version is free with no user cap, while the managed cloud plan prices by user for teams who’d rather not run the infrastructure themselves. Since apps are defined inside ToolJet’s own format, there’s no export to a standalone frontend codebase, though self-hosting keeps your data and app logic under your own control either way. The ceiling is a smaller plugin marketplace than Retool’s and a UI that still shows its open-source roots in a few rough edges. It fits engineering teams that want an open, self-hostable admin-panel builder and don’t want their internal tools bill to scale with headcount.