Next generation user interface and application development in Scala and Scala.js for web, mobile, and desktop.
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app Additional page / screen load logging and added ScreenManager.waitFor… Feb 7, 2019
client Release 0.10.5 Feb 20, 2019
core Added ability to disable Blocked Feb 20, 2019
dom/src Updated Validation.Length message to be shorter Jan 22, 2019
example Added support for BytesContent in response (Resolves #78) Feb 2, 2019
macros/shared/src/main/scala/io/youi Created `macros` module for internal Macro functionality. Aug 23, 2017
optimizer/src/main/scala/io/youi/optimizer Much better integration of HTMLOptimizer and added support to Templat… Mar 29, 2017
project Dependency updates Jan 21, 2019
server/src Fixed bug in 0.10 release causing content-type not to be properly set Feb 2, 2019
serverUndertow/src/main Fixed accidental logging left in after testing Feb 2, 2019
spatial/shared/src Added math operators to Size Jul 22, 2018
stream/src/main/scala/io/youi/stream Migration of Content into content package Dec 28, 2018
ui Creation of Modal trait for Bootstrap integration Jan 26, 2019
utilities/src/main/scala/io/youi/util Re-write of GoogleFont to properly support Canvas and HTML loading wi… Apr 4, 2018
work/logo Better size measuring support and fixes to container Apr 26, 2018
.gitignore Better Delta support to automatically handle HTML in applications whe… Jun 14, 2018
.jvmopts Added jvmopts to fix memory issues when compiling and testing. Mar 30, 2018
.travis.yml Continued work on DSL for server Mar 30, 2018 Create Sep 7, 2017
LICENSE Badges, License, and SBT build setup. Oct 15, 2016 Updated error support in Scala.js Jul 17, 2018
build.sbt Release 0.10.5 Feb 20, 2019
login-example.html Added support for easily adding ad-hoc CSS May 13, 2018
template.html Fixed tests Dec 27, 2018


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Next generation user interface and application development in Scala and Scala.js for web, mobile, and desktop.


There is heavy development going on toward 1.0, but YouI releases are stable and used in several production systems.


YouI is divided into modules of functionality to minimize the dependencies required for your specific usage:

  • app - unification of client and server to write complete applications (Scala and Scala.js)
  • canvas - User Interface implementation on HTML Canvas for greater power and flexibility than HTML provides
  • client - HTTP client for asynchronous request/response and restful support (Scala)
  • communication - communication framework to provide type-safe communication between a client / server (Scala and Scala.js)
  • core - core features generally useful for web and HTTP (Scala and Scala.js)
  • dom - features and functionality related to working with the browser's DOM (Scala.js)
  • example - example and test functionality for applications using youi
  • hypertext - extension functionality for working with HTML in a more powerful way
  • macros - internal macros for various internal uses
  • optimizer - HTML, JavaScript, and Image optimizations to reduce extra overhead from your application
  • server - base functionality for a web server (Scala)
  • server-undertow - implementation of server using Undertow (Scala)
  • spatial - Spatial and math related functionality for Matrix and other operations
  • stream - streaming functionality for on-the-fly processing and modification of any XML or HTML content (Scala)
  • utilities - internal utilities to support the infrastructure of youi

External Projects

Though this project has several sub-modules, where possible, external projects exist to add optional functionality.

  • youi-plugin - An SBT plugin to simplify setting up your youi project.
  • youi-template - Stand-alone server instance to help designers work with HTML templates locally and support integration for developers.
  • youi-designer - User interface designer tool to create, edit, import, export, and generate user interfaces for youi.
  • youi-example - An example project showing the basic usage of youi.


Though YouI provides many modules to accomplish many things, the primary goal of YouI is application development for web, mobile, and desktop. Take a look at the app module for a great getting started tutorial.


More examples are located in the example directory. Run them with sbt


then load http://localhost:8080/ui-examples.html or search with def path: for URLs.