Domain inclusion lists for contextual campaigns
An inclusion list tells a campaign exactly which websites it may buy. Built from category data, it puts ads next to the topics your audience reads, and it keeps spend away from everything else.
This guide walks through the build: choosing categories, cleaning the list, ranking it, sizing it for reach and keeping it current.
What an inclusion list does, and what it does not
Advertisers use two kinds of domain lists. They answer different questions, and most campaigns that buy open web inventory end up using both.
Inclusion list (allow list)
- Names the sites where the campaign may appear, and nothing else.
- Defines context: a cycling brand can stay on cycling, outdoor and fitness sites.
- Caps reach: the campaign can never deliver more than the list allows.
- Needs regular rebuilding, because new relevant sites appear all the time.
- Works best for clear topics, sponsorship style buys and regulated products.
Exclusion list (block list)
- Names the sites the campaign must avoid, and allows the rest.
- Keeps reach wide while removing known problems.
- Protects against unsafe, low quality or made for advertising inventory.
- Needs the same upkeep, because risky domains appear daily.
- Covered in our guide to domain exclusion lists for brand safety.
In short: an exclusion list asks "where must we never be?", an inclusion list asks "where do we want to be?". Contextual campaigns start from the second question and still respect the first.
Why build the list from category data
Many inclusion lists start as a spreadsheet of sites someone remembered. That approach misses the long tail, ages quickly and is hard to explain to a client.
Coverage beyond memory
Categories surface thousands of relevant sites that nobody on the team has heard of, including strong niche publishers.
Repeatable rules
A list defined as "these categories, these countries, minus these risks" can be rebuilt next month with the same logic.
Easy to explain
Clients and auditors see why each domain is on the list: its category, its country and its popularity band.
No personal data
Context targeting needs facts about websites, not about people. That keeps privacy reviews short.
Two taxonomies, one row
IAB content categories describe the topic in detail, while the 59 web filtering categories act as a safety layer.
Stays current
New domains are categorized daily, so a monthly rebuild picks up new relevant publishers and drops lapsed ones.
Building the list in eight steps
The sequence below works for a single campaign or for a library of reusable lists. Write down each decision so the next rebuild applies the same rules.
Write the brief in plain words
Describe the audience and the context, for example "people planning outdoor trips in Germany and Austria". The words become your category map in the next step.
Map the brief to IAB categories
Pick the tier 1 topic and the tier 2 to tier 4 categories that match. Our category taxonomy shows both systems side by side so you can see what each covers.
Decide primary or any category
Counting only the primary category gives a tighter, more relevant list. Accepting any ranked category widens reach, which suits broad awareness.
Filter by country and language
Keep domains attributed to your markets. Decide how to treat sites without a country, since global publishers often fall in that group.
Subtract the safety layer
Remove domains carrying risky web filtering categories, such as Adult, Gambling, Malware / Phishing / Suspicious and Parked / For-Sale Domains, plus your shared exclusion list.
Rank by popularity band
Sort by global and country popularity bands so the most visited sites sit at the top. This lets you cut the list into tiers later.
Sample and review
Open a random sample of fifty to one hundred sites from each tier. If a category pulled in off-topic sites, tighten the mapping and rerun.
Export in the platform's format
Most buying platforms accept a plain text or CSV file with one domain per line. Keep a richer copy with categories for your own records.
Which fields do which job
Each column in a domain record plays a specific role in an inclusion list. Using the wrong one for a job is the most common reason lists turn out too broad or too thin.
| Field | Role in the list | Typical rule |
|---|---|---|
| IAB category, tiers 1 to 4 | Defines the topic | Include tier 2 to tier 4 categories that match the brief |
| Web filtering category | Safety layer | Exclude sensitive and risky categories for this brand |
| Ranked multiple categories | Relevance strength | Primary only for tight lists, any rank for wide lists |
| Country | Market fit | Keep target countries, review unattributed global sites |
| Global and country popularity band | Reach and quality tiering | Tier 1 for top bands, long tail for scale |
| Personas | Audience check | Keep sites whose likely readers match the brief |
Field definitions sit in the data dictionary. Personas are explained in website personas explained.
Sizing the list for reach
An inclusion list that is too short will not deliver, and one that is too long stops being contextual. Tiering solves this: you start tight and open the next tier only when delivery needs it.
Core publishers
Primary category matches the brief and the site sits in a high country popularity band. Few domains, strong context.
Relevant mid tail
Primary category matches, lower popularity band. This is where niche specialists and local publishers live.
Adjacent topics
The brief's topic appears as a secondary category, or a closely related category is primary. Adds scale with some dilution.
Long tail
Matching sites with no popularity band. Useful for scale, but sample carefully because quality varies most here.
A practical rule: estimate the impressions you need, check how much the first tiers can supply on your buying platform, and add tiers until forecast delivery covers the plan with some headroom.
Worked example: an outdoor equipment campaign
An invented brief shows how the rules come together. A retailer of hiking gear wants contextual reach in German speaking markets during spring.
The category map
The rules applied
- Primary category in the first four topics goes to Tiers A and B, the green topics go to Tier C.
- Countries: Germany, Austria and Switzerland, plus German language sites without a country after review.
- Safety layer: remove Parked / For-Sale Domains, Malware / Phishing / Suspicious, Adult, Gambling and Weapons.
- Subtract the agency's shared exclusion list and any domains the client has asked to avoid.
- Rank by country popularity band, then sample fifty sites per tier and drop mismatches by refining the map.
- Export Tier A and B for launch, keep Tier C ready if delivery lags in the first week.
Result: the campaign launches on a few thousand strongly relevant sites instead of a handful of famous ones. Every domain has a recorded reason for being on the list.
Mistakes that quietly ruin inclusion lists
These problems rarely show up in a launch report. They surface weeks later as low delivery, odd placements or a client question nobody can answer.
Parked domains left in
Keyword names in commercial niches are often parked. Remove them first, see parked domain detection.
Tier 1 only mapping
A tier 1 topic such as Travel is huge and mixed. Use deeper tiers to keep the list on brief.
Never rebuilt
A list frozen at launch slowly fills with lapsed and changed sites while new publishers are missed.
News treated as one block
Blocking all news hurts reach and journalism. Include topical sections of news publishers where the platform allows it.
Made for advertising sites
Some sites exist mainly to resell ad impressions. Screen them out using our page on made for advertising sites.
Platform matching ignored
Platforms differ on how they match subdomains and www. Test a few entries before uploading thousands.
Keeping the list current
An inclusion list is a living file. A short routine each month keeps it relevant without rebuilding from scratch every time.
| When | What to do | Why |
|---|---|---|
| Before each new flight | Run the list against the latest data and drop domains that changed category or became parked | Catches changes since the last build |
| Monthly | Rerun the full build with the same rules and compare added and removed domains | Picks up new publishers from the monthly refresh |
| Weekly, for always-on campaigns | Add newly registered domains that reached your topic categories after their rechecks | New sites often add content weeks after launch |
| After a performance review | Move strong performers up a tier and drop sites with poor viewability or fraud signals | Lets results shape the list |
| Quarterly | Review the category map itself against the current brief | Briefs drift, and so do taxonomies |
How the data itself is refreshed is covered in URL database update schedule and freshness.
Inclusion lists by campaign type
The same method bends to very different goals. The main difference is how tightly you map categories and how many tiers you open.
Product launch
Tight map, Tiers A and B, short flight. Context matters more than scale.
Always-on awareness
Wider map with secondary categories, all tiers, monthly rebuild and weekly additions.
Regulated products
Finance, health and alcohol brands keep strict lists and document every rule for compliance teams.
B2B campaigns
Use personas and business topics to reach professional readers on trade and industry sites.
Local and regional
Country attribution and local language sites matter most. Unattributed global sites are often left out.
Private marketplace deals
Use category data to check which domains a curated package really contains before you commit budget.
For the bigger picture of context targeting, read cookieless contextual targeting and the adtech contextual targeting use case.
Sharing lists across a team or with clients
Agencies and trading desks often keep a library of lists. A little structure makes that library trustworthy and easy to reuse.
Store with each list
- The brief in one sentence and the category map.
- Countries, counting rule and tiers included.
- The exclusion lists subtracted, by name.
- The build date and the data snapshot used.
- Who reviewed the sample and what changed.
Licence points to check
- Uploading derived domain lists to your own buying platforms is the normal use.
- Publishing or reselling the underlying category rows is not allowed.
- Agencies serving many clients should confirm the licence covers that.
- Group licences cover companies with several products or desks.
- Details are on the licensing page.
Inclusion lists versus contextual segments
Buying platforms also sell ready made contextual segments. A domain list you build yourself and a segment you rent from a platform solve similar problems in different ways.
| Question | Your own inclusion list | Platform contextual segment |
|---|---|---|
| Who decides the sites? | You, with written rules | The segment provider |
| Can you see every domain? | Yes, it is your file | Often only partly |
| Works across platforms? | Yes, upload the same list anywhere | Usually tied to one platform |
| Page level precision | Domain level unless combined with page signals | Often page level |
| Cost model | Data licence, no per impression fee for the list | Typically a fee on media spend |
Many teams combine both: the domain list sets the outer boundary, and a page level segment narrows placements inside it. The list keeps the boundary auditable even when segments change.
Checking the list after launch
The first days of a campaign tell you whether the list was built well. Watch a few signals and adjust before budget is wasted.
Delivery pace
If spend lags the plan after two or three days, open the next tier rather than loosening the safety layer.
Concentration
If a handful of domains take most impressions, add more Tier B sites so results do not rest on a few publishers.
Placement report
Compare delivered domains with the uploaded list. Unexpected domains point to subdomain matching or platform settings.
Viewability and fraud
Low viewability or invalid traffic on specific domains is a reason to remove them, whatever their category.
Outcome by tier
Report results per tier. If Tier C performs like Tier A, the brief may be broader than you thought.
Spot checks
Look up surprising placements in the domain category checker to see how they are categorized.
Checklist before you upload
Run through these points in a couple of minutes before a list goes live. Each one prevents a problem we see often in campaign reviews.
Category map written down
The topics and tiers used are recorded next to the list, so the next rebuild matches.
Safety layer applied
Risky web filtering categories and the shared exclusion list were subtracted after filtering.
Sample reviewed
Someone opened a sample from each tier and confirmed the sites fit the brief.
Format tested
A handful of entries were uploaded first to confirm how the platform matches domains.
Reach forecast
The platform forecast covers planned impressions, with the next tier ready if not.
Rebuild date set
A date for the next monthly rebuild is in the calendar before launch day.
Frequently asked questions
What is a domain inclusion list?
It is the set of websites where a campaign may show ads, also called an allow list. Anything not on the list is skipped, so the list defines both context and maximum reach.
How many domains should a contextual inclusion list have?
Narrow topical campaigns often work with a few hundred to a few thousand domains, broad awareness campaigns with tens of thousands. Size against the impressions you need and widen in tiers.
Should I use IAB categories or web filtering categories?
Use IAB categories to describe the topic, because they go down to tier 4. Use the web filtering categories as a safety layer to remove adult, gambling, parked or risky domains.
How often should an inclusion list be refreshed?
Monthly is a good default for always-on campaigns, with a quick check before every new flight. Domains lapse, change topic and appear every week.
Do inclusion lists replace exclusion lists?
No. Most teams build the inclusion list from categories and still subtract a shared exclusion list before upload, because the two answer different questions.
Can I include subdomains and apps?
Category data describes registered domains, so check how your platform matches subdomains. Apps use store IDs rather than domains and need their own list.
Does the data contain personal information?
No. Each row describes a website by categories, country, personas and popularity band, so contextual lists work without data about people.
How do I get the category data?
The database is licensed as files in CSV, Parquet or JSON with a lookup API included. See pricing or check single sites with the domain category checker.
Build inclusion lists from over 120 million categorized domains
IAB and web filtering categories, country, personas and popularity bands in one row, delivered as files with a lookup API included.
IAB is a trademark of the Interactive Advertising Bureau, named here only to identify the content taxonomy discussed. URL Categorization Database is not affiliated with, sponsored or endorsed by the Interactive Advertising Bureau.