This document describes and prioritises gaps for the support of Tibetan on the Web and in eBooks. In particular, it is concerned with text layout. It checks that needed features are supported in W3C specifications, in particular HTML and CSS and those relating to digital publications. It also checks whether the features have been implemented in browsers and ereaders. This is a preliminary analysis.

This document describes and prioritises gaps for the support of Tibetan on the Web and in eBooks. In particular, it is concerned with text layout. It checks that needed features are supported in W3C specifications, in particular HTML and CSS and those relating to digital publications. It also checks whether the features have been implemented in browsers and ereaders. This document complements the document Tibetan Layout Requirements, which describes the requirements for areas where gaps appear. It is linked to from the language matrix that tracks Web support for many languages.

The editor's draft of this document will be developed by the Tibetan Layout Task Force, part of the W3C Internationalization Interest Group. It is published by the Internationalization Working Group. The end target for this document is a Working Group Note.

To make it easier to track comments, please raise separate issues or emails for each comment, and point to the section you are commenting on  using a URL.


The W3C needs to make sure that the text layout and typographic needs of scripts and languages around the world are built in to technologies such as HTML, CSS, SVG, etc. so that Web pages and eBooks can look and behave as people expect around the world.

This page documents issues for a given script or language in terms of support by specifications or user agents (browsers, e-readers, etc.).

A summary of this report and others can be found as part of the language matrix.

Work flow

This version of the document is a preliminary analysis

Gap analysis work usually starts with a preliminary analysis, conducted quickly by one or a small group of experts. Then a more detailed analysis is carried out, involving a wider range of experts. The detailed analysis may involve the development of tests, in order to illustrate issues and track results for browsers. The next phase is ongoing maintenance. It is expected that the resulting document will not be frozen: as gaps are fixed, this should be noted in the document. It is also possible that new gaps are noticed or arise, and they can be added to this document when that happens.

As the gap analysis develops, the requirements for features that are problematic should be described in the companion document, Tibetan Layout Requirements. Links to the appropriate part of that document should be added to this document as the material is created. Note that the requirements document should not contain any technology-specific information: all of that belongs here.


This document not only describes gaps, it also attempts to prioritise them in terms of the impact on the local user. The prioritisation is indicated by colour.


It is important to note that these colours do not indicate to what extent a particular features is broken. They indicate the impact of a broken or missing feature on the content author or end user.

Basic styling is the level that would be generally accepted as sufficient for most Web pages. Advanced level support would include additional features one might expect to include in ebooks or other advanced typographic formats. There may be features of a script or language that are not supported on the Web, but that are not generally regarded as necessary (usually archaic or obscure features). In this case, the feature can be described here, but the status should be marked as OK.

The decision as to what priority level is assigned to a described gap is down to the experts doing the gap analysis. It may not always be straightforward to decide. If a given section in this document refers to more than one feature that is broken, each with different impacts on Web users, the priority for the section should be the lowest denominator.

A cell can be scored as OK if the feature in question is specified in an appropriate specification, and is supported by user agents. A specification that is in CR or later and has two implementations in 'major' browsers will count. This means that the feature may not be supported in all browsers yet. (At some point in the future we may try to distinguish, visually, whether support is available in a specification but still pending in major browsers or applications.)

Text direction

See also General page layout & progression for features such as column layout, page turning direction, etc. that are affected by text direction.

Vertical text

Bidirectional text

Characters and phrases

Characters & encoding


Font styles, weight, etc

Glyph shaping and positioning

Cursive text

Transforming characters

Baselines & inline alignment

Grapheme/word segmentation & selection

Punctuation & other inline features

Text decoration

There are some open questions about text decoration that relate to Tibetan. See the following:

  1. ink skipping should conform to glyph shape
  2. Results for text-underline-position: under
  3. How are underlines positioned in Indic text?

༵ [U+0F35 TIBETAN MARK NGAS BZUNG NYI ZLA] and ༷ [U+0F37 TIBETAN MARK NGAS BZUNG SGOR RTAGS] can be used to create a similar effect to underlining or to mark emphasis. It is difficult to use these, however, since they must be positioned centred below a whole syllable. If a syllable is composed of an even number of spacing glyphs, the mark needs to appear between the middle two, so it can't be achieved by using a combining character. Some higher level positioning is required.

For more details see Text emphasis and highlighting in the requirements document.


Inline notes & annotations

Data formats & numbers

Lines and Paragraphs

Line breaking

Need to run some tests to check whether line break as expected on major browsers and ereaders, including prohibited line breaks following NGA, breaking around syllables, etc.

Also check for support for chen spungs shad.

For more information, see the requirements document: Line breaking

See also hyphenation below.


Text alignment & justification

Is tsek padding needed (for basic or advanced use)?

Major browsers seem to only justify by stretching U+0020 spaces after shad. What else should be done for better justification?

For more information see the requirements document: Justification

Letter spacing

Lists, counters, etc.

A counter style is defined in the document Ready-made Counter Styles: tibetan. It is also defined also in the CSS Counter Styles specification.

The tibetan counter style is not supported by Edge (or IE), but is supported by other browsers. (In the case of failure, the style falls back to ordinary european decimal numbering.) See test results.

Styling initials

Layout & pages

General page layout & progression

Footnotes, endnotes, etc.

Page headers, footers, etc.

Forms & user interaction


Culture-specific features

Sometimes a script or language does things that are not common outside of its sphere of influence. This is a loose bag of additional items that weren't previously mentioned. This section may also be relevant for observations related to locale formats (such as number, date, currency, format support).

What else?

There are many other CSS modules which may need review for script-specific requirements, not to mention the SVG, HTML, Speech, MathML and other specifications. What else is likely to cause problems for worldwide deployment of the Web, and what requirements need to be addressed to make the Web function well locally?