Strikethrough



Strikethrough is a typographical presentation of words with a horizontal line through their center, resulting in text like this. Contrary to censored or sanitized (redacted) texts, the words remain readable. This presentation signifies one of two meanings. In ink-written, typewritten, or other non-erasable text, the words are a mistake and not meant for inclusion. When used on a computer screen, however, it indicates deleted information, as popularized by Microsoft Word's revision and track changes features.

Marking errors
Strikethrough is primarily used to mark text that is mistaken or to be removed.

Highlighting
In medieval manuscripts such as the Domesday Book, "strikethrough" of text with red ink often functions as highlighting similar to modern underline.

HTML
The HTML presentational inline element for strikethrough is  or. This element was, however, deprecated in the 1999 HTML 4.01 standard, and replaced by the  tag, a semantic element representing deleted text, which user agents (typically web browsers) often render as a strikethrough.

In the HTML5 draft, there is no presentational element for strikethrough. However, there are two related semantic elements. Firstly,, that is strikethrough in HTML 3 and 4, is redefined to mark text that is no longer correct, and secondly,   marks text that has been deleted, as it does in HTML 4.01.

Other markup symbols

 * BB Code is a markup language used on many web forums. The BB Code for strikethrough is  or  . To end strikethrough when using , type   (ex.  ).
 * GitHub flavored Markdown uses double tilde  (tilde) character, text will be struck out.

CSS
In cascading style sheets (CSS) strikethrough is controlled using the  property, and specified by the   value of that property. For example,  renders like this: ABCD efghi

To maintain backwards compatibility, the following can be added to the CSS:  The example above could then be written like this: , which is compatible with HTML 4. In HTML 5, this:  also produces the same result, although the use of CSS is preferred and the   tag carries a semantic interpretation not present in the purely stylistic   and   tags.

Combining characters
In plain text scenarios where markup cannot be used, Unicode offers a number of combining characters that achieve similar effects.

The "combining long stroke overlay" results in a stroke across the text (may or may not be unbroken depending on the typeface used):
 * A̶B̶C̶D̶ ̶e̶f̶g̶h̶i̶

while the "combining short stroke overlay" results in individually struck out characters:
 * A̵B̵C̵D̵ ̵e̵f̵g̵h̵i̵

Similarly, the "combining short solidus overlay" results in diagonally struck out letters:
 * A̷B̷C̷D̷ ̷e̷f̷g̷h̷i̷

as does the "combining long solidus overlay", which produces longer diagonal strokes:
 * A̸B̸C̸D̸ ̸e̸f̸g̸h̸i̸

Specific struck-through characters
A number of characters that have the visual appearance of struck-through characters exist in Unicode, including ⟨ƀ⟩, ⟨Đ⟩, ⟨Ð⟩, ⟨Ǥ⟩, ⟨Ħ⟩, ⟨Ɨ⟩, ⟨Ɉ⟩, ⟨Ł⟩, ⟨Ɵ⟩, ⟨ꝵ⟩, ⟨Ŧ⟩, ⟨Ʉ⟩, ⟨Ƶ⟩, ⟨ƻ⟩, ⟨ʡ⟩, ⟨ʢ⟩, ⟨Ғ⟩, ⟨Ҟ⟩, ⟨Ұ⟩, and ⟨Ҍ⟩. These usually have specific functions (for example, in the Latin Extended-A character set) or representations and are not intended for general use. However, they are not precomposed characters and have neither canonical nor compatibility decompositions. This issue has created security considerations since "precomposed" characters like U+019F and sequences like U+004F U+0335 or U+004F U+0336 often cause visual confusion (compare ⟨Ɵ⟩, ⟨O̵⟩ and ⟨O̶⟩). Unicode has acknowledged this issue and has proposed a standardized method for counteraction.

For slashed letters in an orthography, unitary letters are provided by Unicode. The diacritics are used in generic applications, such as math operators which systematically use the solidus overlay to indicate negation.

Double/multiple strikethrough
Double strikethrough is an option in certain word processing applications such as Microsoft Word. There is no generally agreed meaning of double strikethrough, but it may be used as a second level of single strikethrough.

In Japan, double strikethrough is conventionally used (rather than single strikethrough) when striking out text. This is for added clarity, as in complex kanji a single strikethrough may be missed or confused with a stroke in the character.

Double, triple or multiple strikethrough may also (especially formerly) be used as a way of emphasising words.

Research
Since at least 2014, researchers in the area of optical character recognition have attempted to solve the problem of recognizing struck-out text in handwritten documents.