15. A computer-implemented method comprising: storing information that indicates, for each hotword of a plurality of hotwords, information that maps a unique identifier of the hotword to a visual representation of the hotword, wherein the visual representation of a first hotword of the plurality of hotwords is visually different from the visual representation of a second hotword of the plurality of hotwords; receiving, from an application on a computing device and based on the application having identified in code for an electronic document a hotword instruction that is dedicated to activating a hotword capability for a particular hotword of the plurality of hotwords identified by the hotword instruction, a request for the visual representation of the particular hotword, the request identifying the particular hotword by its unique identifier; retrieving, using the unique identifier of the particular hotword as specified in the request, the visual representation of the particular hotword from among the visual representations of the plurality of hotwords; and returning, to the application and in response to the request, the visual representation of the particular hotword, wherein the application is configured to render a presentation of the electronic document in which the hotword capability for the particular hotword is activated, including showing the visual representation of the particular hotword in the presentation of the electronic document and enabling the application to respond to instances of spoken input that correspond to the particular hotword.
15. A computer-implemented method comprising: storing information that indicates, for each hotword of a plurality of hotwords, information that maps a unique identifier of the hotword to a visual representation of the hotword, wherein the visual representation of a first hotword of the plurality of hotwords is visually different from the visual representation of a second hotword of the plurality of hotwords; receiving, from an application on a computing device and based on the application having identified in code for an electronic document a hotword instruction that is dedicated to activating a hotword capability for a particular hotword of the plurality of hotwords identified by the hotword instruction, a request for the visual representation of the particular hotword, the request identifying the particular hotword by its unique identifier; retrieving, using the unique identifier of the particular hotword as specified in the request, the visual representation of the particular hotword from among the visual representations of the plurality of hotwords; and returning, to the application and in response to the request, the visual representation of the particular hotword, wherein the application is configured to render a presentation of the electronic document in which the hotword capability for the particular hotword is activated, including showing the visual representation of the particular hotword in the presentation of the electronic document and enabling the application to respond to instances of spoken input that correspond to the particular hotword. 17. The computer-implemented method of claim 15 , wherein the application comprises a web browser and the unique identifiers for the plurality of hotwords are identified from markup code for a webpage that is loaded by the web browser.