Wikipedia:Manual of Style/Accessibility/Data tables tutorial#Correct table captions

• Priority: high (accessibility level: A)
• Difficulty: easy (the syntax is fairly simple and editors get used to it; the layout might change users' habits)

A caption is a table's title, describing its nature.[http://www.w3.org/TR/2008/NOTE-WCAG20-TECHS-20081211/H39 "H39: Using caption elements to associate data table captions with data tables"], accessibility level: A.

Like the caption, these help present the information in a logical structure to visitors.[http://www.w3.org/TR/2008/NOTE-WCAG20-TECHS-20081211/H51 "H51: Using table markup to present tabular information"] The headers help screen readers render header information about data cells. For example, header information is spoken prior to the cell data, or header information is provided on request.[http://www.w3.org/TR/REC-html40/struct/tables.html#edef-TH Table cells: The TH and TD elements], W3C

This clearly identifies headers as either column headers or row headers respectively.See [http://www.w3.org/TR/html5-diff/#absent-attributes HTML5 differences from HTML4, 3.6 Absent Attributes]: "scope attribute on td" will be deprecated in HTML 5. To prepare for the change we should use solely scope attribute on th.[http://www.w3.org/TR/2008/NOTE-WCAG20-TECHS-20081211/H63.html "H63: Using the scope attribute to associate header cells and data cells in data tables"], accessibility level: A

As can be seen in the example above, row headers are formatted by default as bold, centered and with a darker background. This is the common behavior across the Internet, and the default rendering in most browsers. In some circumstances it might be desirable to apply a style customized for a specific case. The class plainrowheaders will apply left-aligned and normal-weight formatting so that editors do not feel the need to override the header formatting with inline CSS declarations for each cell.See the discussions at MediaWiki talk:Common.css [//en.wikipedia.org/w/index.php?title=MediaWiki_talk:Common.css&diff=prev&oldid=395578619#some_wikitable_ideas some wikitable ideas] and [//en.wikipedia.org/w/index.php?title=MediaWiki_talk:Common.css&diff=prev&oldid=395578619#Bold_row_headers bold row headers]. Used by itself, plainrowheaders will make headers appear similar to unmodified data cells, except for the darker background.

To use plainrowheaders, place it (like wikitable) in the class attribute at the beginning of the table. The example below shows an unbolded, left-aligned row header with a custom larger font style:

{{Shortcut|MOS:TABLECAPTION|MOS:TABLESUMMARY|MOS:TABLEHEADINGS|MOS:TABLECAPTIONS}}

{{anchor|Correct table captions|reason=old name, may be linked to}}

Table markup provides for both captions and summaries, both of great utility for making tables accessible. The caption provides a descriptive heading for the table and the summary provides a "nutshell" of its content. If you like, you can think of them as analogous, respectively, to a journal paper's title and its abstract.

• Priority: high (accessibility level: A)
• Difficulty: easy (the syntax is fairly simple and already in use; the layout slightly changes users' habits)

All data tables need a table caption that succinctly describes what the table is about. It plays the role of a table heading, and is recommended as a best practice.{{cite web |title=Ensure table captions are provided explicitly |at="Best Practices" section |author= |work=Accessibility Management Platform (AMP) |year=2015 |publisher=SSB BART Group |location=San Francisco, California |url= https://www.webaccessibility.com/best_practices.php?best_practice_id=415 |accessdate=13 July 2015}} GSA Schedule 70. Cites multiple standards besides WCAG, including: JIS X 8341-3: 2004 - Technical Standards Subpart 5; KWCAG; 47 CFR 14. Advanced Communication Services, §14.21 Performance Objectives; HHS HTML 508 Checklist; and US Telecommunications Act Accessibility Guidelines 1193.41–43. You would usually need some kind of heading or description introducing a new table anyway, and this is what the caption feature exists for. Table captions are made with |+.Table captions can also be made with {{tag|caption|content={{var|Caption here}}}}, and summaries with {{tag|table|o|params=summary="{{var|Summary text here.}}"}}, but wiki syntax should be preferred in articles. A caption can be styled with CSS, and may include wikilinks, reference citations, etc. It may be explicitly put to the left like other Wikipedia headings with style="text-align: left;" (a good idea especially on wide tables). Captions are not used for layout tables (these are deprecated on Wikipedia as well as more broadly, but some editors temporarily resort to them until later editors wikicode whatever it was they were trying to achieve.)

A temporary case for not using the |+ caption is in certain situations when using a collapsible table. {{As of|2010|09}}, the {{nowrap|"[hide]" / "[show]"}} collapse control has to be inside a table header (until the collapsibility script is improved), and it must be large enough to contain it. If the table has no header, or only a very small header, a common solution has been to put the caption text in a table header to which the collapse controller may attach.{{clarify|date=July 2015|reason=Has this problem been resolved yet? It's been almost 5 years.}}

Example of a proper caption from Tobin Bell#Credits:

Captions should be concise; if the table needs an extended introduction, provide one in normal article prose, then provide a simpler caption. However, table captions consisting of a single word like "Actor", "Film" or "Television" – as in a previous revision of [//en.wikipedia.org/w/index.php?title=Tobin_Bell&direction=prev&oldid=383607939#Filmography Tobin Bell's filmography] – are inadequate, as they are not descriptive enough.

{{Shortcut|MOS:COLHEAD}}

• Priority: high (accessibility level: A)
• Difficulty: medium (requires large changes to tables, editors seem reluctant to split tables, needs more testing and feedback)

Do not place column headers in the middle of a table to visually separate the table. For example, a screen reader reading the cell "Stuttgart, Germany" might associate the cell with the following headers: "Venue, Representing Soviet Union, Representing Belarus". Three headers are read aloud. The first and the third are correct and expected. But "Representing Soviet Union" does not apply to the lower half of the table, and a machine does not understand that. Thus, a machine will not be able to associate header and cells correctly, and will provide misleading information about the table structure to the user.

In most cases, the easier solution is to split the table into several sub-tables with explanatory sub-headings (second example).

From Vasiliy Kaptyukh and produced by {{t|AchievementTable}}:

Other similar examples can be found at [//en.wikipedia.org/w/index.php?title=Yvonne_van_Gennip&oldid=372776854#World_records Yvonne van Gennip], Masters Athletics World Records and [//en.wikipedia.org/w/index.php?title=Comparison_of_layout_engines_%28Cascading_Style_Sheets%29&oldid=387933391#Selectors Comparison of layout engines (Cascading Style Sheets)#Selectors].

The first solution where the table is split in several sub-tables.

An alternative which takes a bit more time to implement is to add a column for the representation.

In contrast with simple tables, which only have headers spanning one column (! scope="col" | ) or one row (! scope="row" | ), some headers may span multiple columns or rows with the use of the colspan or rowspan attributes. To clearly define relationships and avoid accessibility issues, use ! scope="colgroup" colspan="2" | when a column header spans two columns and ! scope="rowgroup" rowspan="2" | when a row header spans two rows, adjusting the number if spanning more.

For tables with headers that are more complex, it is recommended to simplify the table or split it up into smaller tables. When this isn't possible, you have to associate each cell to their respective header(s) using the id and headers attributes instead of scope. On the headers, set the id to an unspaced value that is unique on the page. On the cells that are described by headers, set the "headers" to a spaced list of the describing "id" values in an order that a screen reader should read them.[https://www.w3.org/TR/2008/NOTE-WCAG20-TECHS-20081211/H43.html "H43: Using id and headers attributes to associate data cells with header cells in data tables"], accessibility level: A For example, the following markup has the "Company" header describing the "ABC" company (! id="col1" | Company and | headers="col1" | ABC).

Below is an example of a complex table with headers that aren't visually clear, but uses id and headers instead of scope to associate column and row headers to individual cells. Again, it is recommended to simplify the table so headers are visually clear by splitting it into a "d" and "e" table if possible where the text in the "d" and "e" cells are moved to each table's caption.

Note that colors and images with contrast conforming to accessibility requirements will print nicely in grayscale as an induced effect (among other benefits).

• Priority: high (accessibility level: A)
• Difficulty: unknown (needs more testing and feedback for a precise rating)

Images inside a table should meet the general requirements in Wikipedia:Alternative text for images. However, small icons are the principal case encountered in a table. They fall into two categories:

1. icons of symbols ought to have minimal alt text that conveys the same information as the icon (example: if Image:Dark Green Arrow Up.svg indicates an increase it has |alt=increase);
2. decorative icons (icons carrying no information or associated with a text providing similar information) need to be unlinked and have an empty alt text (|link=|alt=). When they are not able to be unlinked, a minimal alt text will suffice.

Note that images in headers can be particularly annoying for screen reader users if they are badly handled. If the image does not comply with the above criteria, the filename will be part of the header title. The filename will be read aloud in every cell under the header containing the icon. The alt text will also be repeated like the filename, which can also be a nuisance if it is irrelevant to the subject or is too long.

• Priority: high (accessibility level: A)
• Difficulty: medium (needs testing and feedback for a precise rating)

Colors inside a table should meet the requirements for color.

• Color contrast – measured by the free [https://www.paciellogroup.com/resources/contrastanalyser/ Color Contrast Analyser] – needs to be sufficient.
• A very simple tool that can be helpful for choosing contrasting colours is [https://colororacle.org/ Color Oracle], a "free color blindness simulator for Windows, Mac and Linux".

But more importantly, information should not be conveyed by color alone. Information should also be available textually. A footnote or a textual signBut avoid Unicode characters, per Wikipedia:Manual of Style (accessibility)#Text. See also [//en.wikipedia.org/w/index.php?title=User_talk:Bamse&diff=385470117&oldid=385349107 Graham87's explanation] in the context of a [//en.wikipedia.org/w/index.php?title=Wikipedia%3AFeatured_list_candidates%2FList_of_National_Treasures_of_Japan_%28crafts%3A_swords%29%2Farchive1&action=historysubmit&diff=385510315&oldid=385430878 featured list candidate.] can also be used to show a cell has a particular meaning.

From [//en.wikipedia.org/w/index.php?title=Fiscal_year&oldid=384026890#Chart_of_Different_Fiscal_Years Fiscal calendar#Chart of Different Fiscal Years]:

Note: This is an example of using color rather than of providing accessible tables. Having the table caption in a table header instead produces a non-accessible table.

Legend: cells marked with "{{chk}}" are included in the fiscal year.

From Dwain Chambers (with improved table caption and structure; but the original use of color is good):

• Priority: high (accessibility level: A)
• Difficulty: unknown (not yet rated)

Nested tables can be confusing for screen reader users, however with correct usage they can be navigated as well as any other coding approach to the desired display.

The key principle in their design and implementation is to maintain normal flow, i.e. to ensure that the ordering of the content in the page code matches the order in which the content is to be presented. This also applies to other coding approaches, such as divs with CSS styling, or rowspan and colspan HTML cell attributes.

Nesting data tables with header cells also makes it difficult for assistive readers to parse them sensibly, and should be avoided.

Nesting tables may be the most appropriate method where cells of the parent table are to be subdivided with uneven internal row or column breaks. Note that each table must begin on a new line.

In the following example, nested tables are used to display sub-tables of varying cell heights:

By comparison, using rowspan would not only need careful juggling of the positions and values but would break normal flow, splitting up each data subset and even causing Insert 3down and Insert 4down to be read in the wrong order:

CSS also has table display properties which can be applied to other elements such as divs, and could be used to create the layout with correct normal flow. But it requires a custom stylesheet defining the various classes of substitute entity. Moreover, it breaks the formal separation of HTML structure vs. CSS styling by using the styling language to render the correct structure onscreen. It is unnecessary and is not recommended.

Additional information can be found at Data tables tutorial/Internal guidelines‎‎. However, this guideline is not meant to be enforced, and only serves as a resource for members of WikiProject Accessibility.

These are examples of tables read aloud by screen readers. They may be useful as concrete examples to show to the community, when the community has difficulty in understanding how an accessible table benefits a screen reader user.

• [http://bennett1.org/a11y-prg/tbl/134-tbl-scope-attr Table using SCOPE attributes]{{dead link}} (NVDA using the Crystal voice from NaturalSoft)
• [http://bennett1.org/j15/accessibility/at-testing/tst-sr/tables-screen-readers/171-tables-using-id-attribute Table using ID attribute]{{dead link}} (NVDA using the default eSpeak voice)

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Data tables tutorial

Category:Wikipedia essays and information pages about the Manual of Style

Category:Wikipedia tables

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