Buy-side ad tech is the software that advertisers and their agencies use to plan a campaign, make the ads and buy ad space. An advertiser is the business that pays for an ad, such as a paint company or a bank. The buy side is also called the demand side, because it is the side that wants to buy ad space.
Consider a paint company planning its ads for the weeks before Diwali. Its agency, a firm that plans and buys ads for brands, first decides how much to spend on TV channels, news sites, apps and online video. The agency records the plan, the orders and, later, the bills in media planning and buying software.
Next come the ads themselves. In advertising, the ad itself, meaning its image, video and words, is called the creative. Dynamic creative optimisation (DCO) builds many versions of one ad from separate parts. A viewer in Uttar Pradesh may see the ad in Hindi with a festive offer, while a viewer in Kerala sees it in Malayalam with a different offer.
Then comes the buying. Every time someone opens a page or an app with an empty ad slot, the slot is sold in an auction that lasts a fraction of a second. A demand-side platform (DSP) is the advertiser's bidding software. For each slot, it decides whether to bid, meaning to offer a price, and how much to offer. One common use of a DSP is retargeting, which shows ads to people who have already visited the advertiser's website. To recognise one person on a phone, a laptop and a TV, the DSP may use an identity graph, which links the devices and email addresses of one person.
An AI advertising platform does much of this work by itself. The advertiser gives it a goal and a budget. The software then chooses the audience, makes the ads and moves money between campaigns. It is an early case of agentic commerce, in which AI software spends money on someone's behalf.
Some advertisers must follow special rules. Healthcare advertising platforms reach patients and doctors for medicine makers, while obeying health-privacy laws.
All these tools now depend more on first-party data, the data that a brand collects itself from its own website, app and stores. The reason is that third-party cookies, which once let advertisers follow people from site to site, are being restricted by browsers and privacy laws.