Internationalization tests

This page groups together pages being developed by the W3C Internationalization Working Group to assess internationalization support of user agents. It is an ongoing effort.

Note that these tests do not only test conformance with W3C standards. In some cases the tests also allow for exploration of the behavior of user agents in ways not described by the standards.

See the GitHub repo and the notes on how the test suite works.

Jump to one of:
Internationalization test suite tests & results
Interactive tests & results.

Interactive tests

Interactive tests are particularly useful for gap-analysis work or for creating quick ad-hoc tests. You can create a new test, or find recorded tests with their results. For more information, click on the link just below.

Interactive test files provide flexibility and ease of use that is useful for experimental or gap-analysis testing. See Working with interactive tests.

Results summary pages

Pages that group test results by topic. Click on links to see detailed result information or to open the test.

Test rig

The test rig allows you to set up tests yourself and produce a URL to reproduce the page which can be shared or stored.

Older test rigs, no longer used for new tests.


Each repository is effectively a database of test links and results. Each stored test is maintained and discussed in a GitHub issue in one of these repos. The results pages pull their information from the repositories.

Internationalization test suite tests & results

The links below point you to pages that sumarise results across major browsers for features described in W3C/WhatWG specs. From the results pages you can link to the tests themselves, which run within a test framework. You can also run the tests and provide a set of results that can be incorporated into these pages.

CSS Counter Styles

Custom styles

Simple predefined counter styles

Complex predefined counter styles

CSS Logical Properties and Values

Flow-relative values

  • 2.1. Logical Values for the caption-side Property
  • 2.2. Flow-Relative Values for the float and clear Properties

Box Model Properties

CSS Ruby

Ruby Box Model

Ruby Formatting Properties

  • 4.1 Ruby Positioning: the ruby-position property
  • 4.2 Sharing Annotation Space: the ruby-merge property
  • 4.3 Ruby Text Distribution: the ruby-align property

Custom Counter Styles

Exploratory tests

CSS Pseudo


CSS Syntax

Character encoding

CSS Text

Text transform

White space

Line breaks

Word breaks

Alignment & justification

Cursive boundaries

CSS Text Decoration

Line decoration

Text emphasis

Text shadow

CSS Writing Modes


Vertical text



Language selection

  • 6.3.1. Attribute presence and value selectors
  • 6.6.3. The language pseudo-class :lang


Character encoding


Text direction


The q element


Encoding spec

Single-byte encodings

Double-byte encodings

Other tests

The following is a mixed bag of additional tests.

Exploratory tests


Justification & letter-spacing

Cursive behaviour

Language and fonts

Text selection

Older tests (still using old frameworks)

CSS selectors


HTML character encoding