Hidden text is computer

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 text that is displayed in such a way as to be invisible or unreadable. Hidden text is most commonly achieved by setting the font

Typeface

In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....

 color to the same color as the background, rendering the text invisible unless the user highlights it.

Hidden text can serve several purposes. Often web sites use it to disguise spoiler

Spoiler (media)

Spoiler is slang for any element of any summary or description of any piece of fiction that reveals any plot element which will give away the outcome of a dramatic episode within the work of fiction, or the conclusion of the entire work. It can also be used to refer to any piece of information...

s for readers who do not wish to read that text. Hidden text can also be used to hide data from users who are less Internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

-savvy or who are not familiar with a particular website. An example of this practice is to display an FTP

File Transfer Protocol

File Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...

 password in hidden text to reduce the number of users who are able to access downloads and thereby save bandwidth.

It is also used by websites as a spamdexing

Spamdexing

In computing, spamdexing is the deliberate manipulation of search engine indexes...

 technique to fill a page with keywords

Keywords

Keywords are the words that are used to reveal the internal structure of an author's reasoning. While they are used primarily for rhetoric, they are also used in a strictly grammatical sense for structural composition, reasoning, and comprehension...

 that a search engine

Search engine

A search engine is an information retrieval system designed to help find information stored on a computer system. The search results are usually presented in a list and are commonly called hits. Search engines help to minimize the time required to find information and the amount of information...

 will recognize but are not visible to a visitor. However, Google

Google

Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...

 has taken steps to prevent this by parsing the color of text as it indexes it and checking to see if it is transparent, giving those pages much lower rankings.

Compare with metadata

Metadata

The term metadata is an ambiguous term which is used for two fundamentally different concepts . Although the expression "data about data" is often used, it does not apply to both in the same way. Structural metadata, the design and specification of data structures, cannot be about data, because at...

, which is usually also hidden, but is used for different purposes.

Hidden characters are characters that are required for computer text to render properly but which are not a part of the content, so they are hidden. This includes characters such as those used to add a new line of text or to add space between words, commonly referred to as "white space characters".