Tech, ExplainedGaming, streaming and media
Concept

Contextual advertising

Ads chosen by the page, not the reader.

HOW IT WORKSA reader opens a pagewith an empty ad slotSoftware reads thepage's words, imagesor videoIt labels the pagewith topics and checksit is safe for brandsAdvertisers whowant that topicbid for the slotThe matched adappears, with no dataabout the readerThe page itself tells the advertiser what the readeris interested in, so no personal data is needed.HOW IT WORKSA readeropens a pagewith an emptyad slotSoftwarereads thepage'swords, imagesor videoIt labelsthe pagewith topicsand checksit is safefor brandsAdvertiserswho want thattopic bid forthe slotThe matchedad appears,with nodata aboutthe readerThe page itself tells the advertiser what the readeris interested in, so no personal data is needed.HOW IT WORKSA reader opens a pagewith an empty ad slot↓Software reads the page's words, imagesor video↓It labels the page with topics and checksit is safe for brands↓Advertisers who want that topic bid forthe slot↓The matched ad appears, with no dataabout the readerThe page itself tells the advertiser what the reader isinterested in, so no personal data is needed.
Software reads the page and labels its topic, advertisers bid for readers of that topic, and the matched ad appears without any data about the reader.
opens a page inside this one a page in the same scene a page in another scene a concept page a label only, with no page

Contextual advertising means choosing an ad by what a web page, app screen or video is about, rather than by who is reading or watching it. An ad for cooking pans appears beside a recipe. An ad for running shoes appears beside a marathon report. The advertiser needs no data about the reader at all.

For years, most online ads were chosen the other way, by the person. A third-party cookie, a small file stored by the browser, let advertisers follow each reader from site to site and build a profile of what they had looked at. Privacy laws, such as India's DPDP Act, and browser makers are now restricting this. So advertisers are returning to the page itself.

Here is how it works in general. A reader opens a page with an empty ad slot. Software reads the page: its words, and often its images and video too. It labels the page with topics, such as "recipes", "cars" or "personal finance". It also checks whether the page is safe for brands, for example whether it reports a crime or a disaster. The publisher's selling software, the supply-side platform, sends these labels with the offer of the ad slot. Advertisers who want readers of that topic bid for the slot. The winning ad, matched to the topic, appears on the page.

Take, for example, a niche news site about health. An article about managing diabetes can carry an ad for a glucose meter, because every reader of that article has chosen the topic.

Consider a video about trekking in the mountains. A contextual ad network can read the video's title, speech and images, and place an ad for warm jackets before it.

Say an airline does not want its ads next to a report of a plane crash. Contextual software, often together with ad verification, keeps its ads off that page, even though the page is about air travel.

How is contextual advertising different from behavioural targeting, such as retargeting? Behavioural targeting chooses the ad by the person: what they searched for, which shops they visited and what they left in a cart. It needs data about each reader, often collected across many sites. Contextual advertising uses only the page in front of the reader, so it works without cookies or personal data. Its weakness is that it knows the topic but not the person, so a reader who has already bought the pans still sees the ad.

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