Both come from Asial Corporation in Tokyo. Monaca, in beta since March 2012, is a commercial service built on Cordova 129 : a browser IDE with live preview, a Monaca Debugger app that runs your code on a phone over the network, and cloud builds that return a signed APK, App Bundle or iOS package without a local Android SDK or a Mac. The free plan has the IDE, 250 MB and one debugger connection, but no builds, and archives projects idle for 180 days; builds start with the Developer plan at $22 a month, then Pro at $77 and Business at $1,100. The Monaca CLI (npm 2,036 install -g monaca, 5.1.0) links a local folder to the cloud.
Onsen UI 450,074 (github.com/OnsenUI/OnsenUI (https://github.com/OnsenUI/OnsenUI 8,856 ), Apache 2.0, 2.12.9) is Asial's free UI kit and Monaca's default. Like Ionic 20,753 it is made of custom elements, such as <ons-page>, <ons-toolbar> and <ons-list-item>. It styles them as Material Design 15,533 on Android and as iOS elsewhere, and ons.platform.select('android') forces one look. Its last commit was in June 2026 and its 8,856 GitHub 29 stars grow slowly: it is maintained rather than developed. It suits a Monaca project; for an app on your own toolchain, Ionic and Framework7 572,986 have more momentum.