The triumph of social networks over the last ten years has also been a triumph for the keyword. Ever since Twitter and Instagram introduced the “hashtag” – in 2007 and 2010, respectively – a form of organizing statements and documents that not long ago was restricted to highly specialized professional circles has characterized the everyday use of media. In what contexts, then, did “keywords” play a role just a quartercentury ago? Something like this concept was approximated in the library and archival sciences, which, since the early twentieth century, had been developing increasingly standardized “subject catalogs” in order to make it easier to locate documents. Elsewhere, they featured in historical keyword or catchword research, a subdiscipline of linguistics concerned with analyzing the formative expressions of a given epoch or political movement. Both of these venues, however, exist on the margins of academia, and thus it can be said without a doubt that the category of the “keyword” had occupied a rather inconspicuous position before the turn of the twenty-first century. It was the establishment of the hashtag that quickly shoved this niche element into the spotlight of our present-day media reality. Today, every Twitter feed and Instagram post provides further testimony to the collective indexing or “keywording” of the world, which can be undertaken by any user of these social networks as a creative act that is unrestricted by preinstalled standards or hierarchically tiered modes of access.

In the early years of the “World Wide Web,” as is well known, documents could only be connected to one another through a system of “hyperlinks.” Highlighted in advance, certain words or passages of a text would lead, when clicked upon, to another place on the same website, or to a different website altogether. In many respects, the transition from the “link” to the “hashtag” as a defining networking principle was a major shift in the digital organization of statements. First, it meant that every internet user could create links independently and without any knowledge of programming, and thus it paved the way for the highly touted “social” and participatory era of the internet. Second, it meant that a method for creating links had been endowed for the very first time with a typographical element of its own. The prefixed symbol “#” – known as a “hash” in British English and as a “pound sign” or “number sign” in American English – transforms words into networked keywords. The hashtag and the letters immediately following it thus have two functions: they are both a component of visible tweets or Instagram posts and a trigger for the invisible procedure that links them together.

In linguistic terms, the hashtag thus exists on the threshold between text and metatext, and it draws the previously hidden steps of cataloging and indexing out into the open. As a binding element between everyday communication and computer code, it has become the most popular signature of the present, and its effectiveness is most clear to see in the fact that the pound/hash sign has since begun to appear beyond screens and displays. The # symbol can now be found in the titles of recent novels, on T-shirts, on signs held at political demonstrations, in graffiti, in advertisements on the side of the road and even in tattoos. In a world made of stone, paper, cotton, and skin, the hashtag cannot be clicked on and it cannot link to anything, but even on these materials it can represent a pledge – a pledge to be seen, find an audience, and pool interests. Thus the # is no longer a purely functional sign – for some time, in fact, it has also been a promising social symbol. It stands for the production and accumulation of public attention.

The hashtag is implemented so widely in today’s media reality that it is easy to overlook the elementary effects that it has had within the past few years on the order of statements and on the structural principles of debates. The following book, which is concerned with the origin and the diverse social effects of the hashtag (and the # symbol in general), is an attempt to close this gap. First published in 1956, Theodor W. Adorno’s famous article on typography begins with these words: “The less punctuation marks, taken in isolation, convey meaning or expression, … the more each of them acquires a definitive physiognomic status of its own.”¹ A good 60 years later, it is time to consider the “physiognomic status” of the hashtag in today’s digital culture, and particularly to consider the extent to which this symbol has influenced such things as the use of language or the creation of collectives.

The subject of my book is the remarkable career of the # symbol in the history of media. Here, I will examine how the “keyword” was used before the hashtag entered the scene, and I will discuss the symbol’s most prominent areas of application during the last decade (political activism and marketing). Finally, I will look at the ways in which the hashtag has influenced socio-political movements. For it was this last aspect that, at the beginning of 2018, provided the impulse for the following considerations. It was around this time that the “#MeToo” movement took shape and incited a global, epoch-making debate about sexual violence – a debate that, over the course of several months, generated thousands of daily tweets and dozens of articles in newspapers, online portals, and blogs. The positions and legitimations of this debate have since been discussed in all of their facets; in the meantime, “#MeToo” has become a common expression and can now be found in the content pages of news magazines as a self-explanatory rubric. So far, however, hardly anyone has asked about the extent to which the media and linguistic circumstances of this debate have influenced the development of its content. To what extent, for instance, do the recurring misunderstandings and conflicts between its participants about the definitions of “harassment” or “abuse” stem from the specific way that they have used hashtags to organize their statements? For, when the various and diverse voices sharing their experiences with sexual violence all do so under the same, identity-forming keyword – “#MeToo” – this only serves to strengthen the very tendencies toward homogenization and leveling that have received so much criticism within the debate itself.

The hashtag, which has seemingly contributed so much in recent years to the formation of the public sphere, brings statements together and forms collectives. At the same time, however, it also smooths over differences and thus obscures subtleties that do not conform to a single neat rubric. This book is an attempt to fathom the power of a symbol that, until recently, was no more than a mysterious typewriter key or button on a telephone.