Support for Text Customization

This page provides information on how tools and technologies and accessibility standards and guidelines support users' need to customize text.

For context, please read Text Customization for Readability.


Support in tools and technologies

The tools that people use to interact with electronic text - web browsers, PDF readers/viewers, and e-book readers - are called "user agents". User agents have varying support for text customization.

Word processing programs

Word processing programs allow users to customized all aspects of text display.

Web browsers

Most mainstream web browsers provide functionality for users to customize font face, text size, text color and background color; and provide zoom functionality that rewraps to avoid horizontal scrolling in many cases. Improving the usability of such functionality is an importance issue (for example, it can take 20 steps to change font color in a common browser) that is outside the scope of this page.

Most browsers provide functionality for users to set their own style sheets and customize all aspects of text display. However, this is an advanced feature. Currently, creating and using user style sheets requires knowledge of CSS (cascading style sheets) and browser functionality that is beyond most users' knowledge. (About user style sheets at the end of this page has more info.)

PDF readers/viewers

Adobe Reader and other PDF viewers do not provide functionality to set most aspects of text display that people need in order to read text effectively.

Adobe Reader does not provide functionality for users to set font face, leading/line spacing, element-level customization, and most other aspects of text display. It does provide functionality to set text and background colors, zoom, and reflow (which temporarily puts text in a single column); however, there are significant limitations to the latter two, described below.

Reflow does not work for some pages, including all pages with form fields. Adobe says of Reader’s reflow limitations: "Text that does not reflow includes forms, comments, digital signature fields, and page artifacts, such as page numbers, headers, and footers. Pages that contain both readable text and form or digital signature fields do not reflow." [reference]

In reflow mode, the search/find-in-document feature does not work at all. Search is a "fundamental" requirement in Daisy Consortium's checklist for eReaders. [Daisy]

Reader's zoom functionality does not reflow text to avoid users having to scroll horizontally. Documents with some layouts are not functionally readable to some users with zoom that does not reflow, such as research papers formatted in two columns. When users get to the bottom of a column, they have to scroll up to find the top of the next column and the physical and cognitive effort required can break the flow of reading and understanding substantially. Comments in the User Research Survey included:

(There is also a usability problem with zoom. There are limited presets — between 150% and 1600%, the options are only: 200, 400, 800. Users can type in a different zoom level; however, that is not apparent from the user interface.)

PDF documents cannot be printed with customized colors, zoomed, or reflowed. The importance of printing for people with dyslexia is described in [Rainger]. When asked in a User Research Survey how important it is to be able to print customized text, 86% of the answers were Very important or Important. (Learn more about the survey results and the importance of printing customized text.) Abobe Reader only prints text as it was originally formatted.

To my knowledge, currently no PDF viewer provides the text customization that users need. VIP PDF-Reader, which was released 24 June 2013, provides the most text customization of any viewer that I know of, although it is still insufficient.

PDF files are not accessible today

With the technology currently available, PDF files are not sufficiently accessible to many people with low vision, dyslexia, and related conditions that impact reading. This is a significant issue because of the widespread use of PDF as the only way of providing large amounts of essential information, such as tax instructions, scientific papers, educational material, medical information, etc.

Of particular concern is the lack of awareness that PDF files are not sufficiently accessible. After Adobe Reader improved screen reader access, the term "accessible PDF" became widely used. It seems that many managers, policy makers, and even accessibility specialists and disability advocates are not aware of the specific PDF accessibility barriers described above. For many people with print disabilities, there currently is no such thing as "accessible PDF" because they cannot customize the text to be sufficiently readable.

E-book readers

Most e-book readers do not provide functionality to set most aspects of text display. Some provide functionality for choosing from a limited number of pre-defined text sizes, fonts, colors, and line spacing. [reference]

Support in standards and guidelines

Text customization is not sufficiently covered in some accessibility standards, for example, the Section 508 standards.

Now is the opportune time to ensure that text customization is sufficiently addressed in User Agent Accessibility Guidelines UAAG 2.0, which is currently a mature Working Draft.

It is important to clarify how Web Content Accessibility Guidelines WCAG 2.0 addresses text customization, and if updates are needed to the standard or supporting material to provide sufficient coverage of users' needs for text customization.

One issue with coverage of text customization in accessibility standards may be related to legibility versus readability. See the Readability beyond legibility section of Understanding Users' Needs to Customize Text Display. I assume that most of the accessibility guidelines for websites are focused on small amounts of text, such as website navigation, forms, and short descriptions. Thus the guidelines may be sufficient for legibility, but not for readability. They may not be sufficient for things like PDF files that are often used for providing large amounts of text, where readability is essential. To read large amounts of text, users need to be able to customize more aspects of text display, as mentioned by Petri (2011) and supported by this project.

Referring to this material

Please be careful in referencing the information on this website as from the individual Shawn, not related to her employer.

Some of the information on this page is published in peer-reviewed papers, which might be better for referencing in scientific papers and such. See Research for links to the papers.

Depending on what format you use, a reference for this page might be:

Henry, Shawn Lawton. (2013) Support for Text Customization. Available: Last accessed 1 January 2013.

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Notes and References

About user style sheets:

CSS (cascading style sheets) can be used to set how text is displayed in websites (including web pages and web applications). The text display of most websites is defined through author style sheets, that is, style sheets created by the website developer. Most web browsers allow users to override author styles through user style sheets (USS). Thus, users can define how text is displayed in websites by creating their own user style sheet. Users can set global USS that apply to all websites, and can set USS for specific websites. Styles can able be applied through bookmarklets or add-ons such as Stylish (

Dick (2006) describes one process for developing user style sheets. Currently, creating and using USS requires knowledge of CSS and browser functionality that is beyond most users' knowledge. (One user said, "It's a lot of stinkin' work to undo the damage that sites do [with their CSS]".) Therefore, a challenge for this study was finding people who use USS.


For More Information

Shawn Henry