Programmatic Advertising Explained: A Media Buyer's Guide

By Anna Sundberg

Performance Marketing Specialists Reviewed by Senior Media Buyers

Published April 2, 2026

13 min read · Strategy

Programmatic advertising, the automated buying and selling of digital ad inventory through technology platforms, now accounts for over 85% of all display ad spending. Despite its dominance, programmatic remains one of the most misunderstood areas of digital marketing. This guide cuts through the jargon for media buyers and marketers who want to harness this powerful channel.

What Is Programmatic Advertising?

Programmatic advertising is the automated process of buying and selling ad inventory through software platforms in real-time. Rather than negotiating individual ad placements with publishers manually, programmatic uses algorithms and data to purchase ad impressions across thousands of websites and apps simultaneously, targeting specific audiences at optimal prices.

How Programmatic Works

The Ecosystem

The Real-Time Bidding (RTB) Process

When a user visits a webpage, the following happens in under 100 milliseconds:

1. User loads a webpage with available ad slots
2. The publisher's SSP sends a bid request to the ad exchange, including user data (anonymous ID, location, device, etc.)
3. The ad exchange forwards the bid request to connected DSPs
4. DSPs evaluate the impression against advertiser campaigns and submit bids
5. The ad exchange selects the winning bid (typically second-price auction)
6. The winning advertiser's ad is served to the user
7. All of this happens before the page finishes loading

Types of Programmatic Buying

Open Auction (RTB)

The most common form. Impressions are auctioned in real-time to the highest bidder. Offers the widest reach and lowest prices, but less control over where ads appear. Suitable for awareness campaigns with broad targeting.

Private Marketplace (PMP)

Invitation-only auctions where select advertisers bid on premium publisher inventory. Better brand safety, higher quality placements, and more transparency, but at higher CPMs. Ideal for brand advertisers who need quality control.

Programmatic Guaranteed (PG)

Direct deals between advertisers and publishers executed programmatically. Fixed price, guaranteed inventory, specific placements. Combines the efficiency of programmatic with the certainty of direct buys. Best for premium, brand-safe campaigns with specific placement requirements.

Preferred Deals

Non-guaranteed deals at pre-negotiated prices. Advertisers get right of first refusal on specific publisher inventory before it goes to open auction. Good balance of quality and flexibility.

Targeting Capabilities

• Contextual targeting: Place ads alongside relevant content (e.g., sports equipment ads on sports websites). Growing in importance as cookie-based targeting declines.
• Behavioural targeting: Target users based on browsing history, purchase behaviour, and online activity across multiple sites.
• Demographic targeting: Reach specific age groups, genders, income levels, and education levels through data provider integrations.
• Geographic targeting: Target by country, region, city, or even specific GPS coordinates. Essential for local businesses and geo-specific campaigns.
• Device targeting: Serve different creative to desktop, mobile, tablet, and connected TV devices.
• Retargeting: Re-engage users who have previously visited your website or interacted with your brand across the programmatic ecosystem.

When to Use Programmatic vs Platform-Direct

Programmatic works best as a complement to platform-direct campaigns. See our multi-platform strategy guide for how to integrate programmatic with Google Ads, Meta, and other channels.

Brand Safety Considerations

• Use pre-bid brand safety tools (IAS, DoubleVerify, Oracle GRPM) to filter unsafe inventory before bidding
• Implement site inclusion and exclusion lists to control where ads appear
• Use Private Marketplace (PMP) deals for brand-sensitive campaigns
• Monitor placement reports regularly and update exclusion lists
• Consider ads.txt verification to reduce domain spoofing fraud

Getting Started with Programmatic

1. Choose a DSP: For small to mid budgets, consider self-serve DSPs like StackAdapt, Basis, or Amazon DSP. For larger budgets (£50K+/month), The Trade Desk or DV360 offer more sophisticated capabilities.
2. Set your budget: Minimum viable programmatic budgets start at £5,000 to £10,000/month. CPMs range from £1 to £5 for run-of-network to £15 to £40+ for premium PMPs.
3. Define your targeting: Start broad and refine based on performance data. Layer contextual, behavioural, and demographic targeting gradually.
4. Prepare creative: Develop multiple ad sizes (300x250, 728x90, 160x600, 320x50 at minimum) plus native ad formats and video if applicable.
5. Measure and optimise: Use view-through conversions and multi-touch attribution to properly measure programmatic's contribution to your marketing mix.

For help with programmatic strategy, explore our managed campaign services and the Complete PPC Strategy Guide.