The Kotlin Programming Language Website
CSS JavaScript HTML Python XSLT
Latest commit 44885a3 Jan 19, 2017 @belovrv belovrv committed on GitHub update site for 1.1
Merge remote-tracking branch 'JetBrains/master'

This is the source for the Kotlin Web Site

Filing Bugs

We use YouTrack for bug reports and suggestions. Click here to report an issue.



  • Python. Kotlinlang is Flask-based site, so you'll need python 2 to get it working.
  • ruby + kramdown. Python has a very poor support for markdown, so kramdown is used as markdown to html converter
  • nodejs + npm to build frontend assets


After installation of required tools run npm i to download all frontend dependencies and pip install -r requirements.txt to download backend dependencies.

Working with site

Run site

  • Use npm run build command to build assets. If you are going to modify js/scss files use npm start instead.
  • To run site use python command


All data is stored in the *.yml files in folder _data:

  • _nav.yml site navigation and PDF building.
  • releases.yml info about releases.
  • videos.yml data for the Videos page. The content property is used to create categories. It contains a list of videos or other categories. Maximum tree depth level is 3.
  • events.yml event data.


Kotlinlang uses Jinja2 templates that can be found in templates folder. Note, that before converting to html all markdown files are processed as jinja templates. This allows you to use all jinja power inside markdown (for example, build urls with url_for function)

Page metadata

Every page can have an unlimited number of metadata fields. More information here. The most important of them are the page template (e.g. layout: reference) and its type (e.g. type: tutorial). category and title fields are added for future development.

Kotlin grammar reference

The Kotlin grammar reference (grammar.xml) is generated by the Kotlin grammar generator from the Kotlin grammar definition.

Writing content


Kramdown with some additions (like GitHub fenced code blocks) is used as markdown parser. See the complete syntax reference at Kramdown site.

Specifying page element attributes

With Kramdown you can assign HTML attributes to page elements via {:%param%}. E.g.:

  • *important text*{:.important} - produces <em class="important">important text</em>
  • *important text*{:#id} - produces <em id="id">important text</em>

For block elements this instruction must be specified on the line following element definition:

This is a paragraph

This is a paragraph

More information about attributes can be found here.

Custom element styles

Inline elements

  • {:.keyword} highlights a keyword.
  • {:.error} highlights an error.
  • {:.warning} highlights a warning.


  • {:.wide} stretches a table to occupy the entire width of a page.
  • {:.zebra} interleaves table rows.


| Expression | Translated to |
| `a++` | `` + see below |
| `a--` | `a.dec()` + see below |

Quotation blocks

They're used in a slightly other manner that they were originally designed for: as universal block container elements.

  • {:.note} highlights a note block.


> **`inc()/dec()` shouldn't mutate the receiver object**.
> By "changing the receiver" we mean `the receiver-variable`, not the receiver object.