museum-digital is an initiative aimed at allowing museums to easily and effectively manage and publish their (collection) data without compromising on data quality. Founded in 2009 by a group of smaller museums in Saxony-Anhalt with a strong focus on collaborative publication, museum-digital's scope has since expanded to offering solutions for much of the collection-related work of museums and working with over a thousand museums.
I personally have been helping out on museum-digital's software side regularly since about 2015 and have essentially taken over the role of a maintainer of most of the relevant software projects.
Using CSVXML, museums can generate templates for simple imports to museum-digital and validate their import data.
To the user, the tool works entirely on the client-side as a progressive web app. This also means that it may be used entirely offline.
To however pull in updates to controlled lists of available values and translation files from the rest of museum-digital, the tool is written as a very simple static site generator.
The main instance of the tool can be found here. It is licensed under AGPL 3 with source code available here.