Cognism vs ZoomInfo for B2B Data: What Each Vendor Actually Claims

The question behind "Cognism or ZoomInfo"

I'm Hlib Storchak. I build outbound systems for B2B founders and sales teams, and I have booked over 2000 meetings for B2B clients running lists sourced from data providers including both of these. This question comes up almost every time a client is expanding into Europe, or hiring their first SDR who calls instead of just emailing.

The honest answer is that "which is more accurate" is the wrong first question. Both vendors publish their own accuracy claims, both claims are self-reported, and the loudest third-party number comparing the two traces back to a single data-cleaning company's own marketing page, not a disclosed test. So this article does two things: it lays out exactly what each vendor claims about itself, with a link so you can check it, and it gives you a way to decide that does not depend on trusting either page.

The one-line difference

Cognism was built out of London with European compliance and phone-verified mobile numbers as its core pitch. ZoomInfo was built out of the US with database scale and account-level intelligence as its core pitch. Everything else in this article follows from that split.

What Cognism's own comparison page claims

Cognism runs a page comparing itself directly to ZoomInfo. On its own page, Cognism claims:

• 85% data accuracy, self-reported, with no independent audit cited.
• A self-reported 34% contact rate improvement for customers who switched over from ZoomInfo, with no sample size, date range or methodology disclosed.
• Do Not Call and suppression list checks in 15 countries by its own count, including the UK, the US, Australia, and nine named European registers (Germany, France, Italy, Spain, Ireland, Belgium, Croatia, Portugal and Sweden), against what the same page describes as 8 countries for ZoomInfo.
• European data included as standard, positioned against ZoomInfo charging extra for it.
• Rolling monthly subscriptions as the contract model, contrasted with ZoomInfo's annual commitment.

Read that list the way you would read any vendor's page about a competitor: every claim about Cognism itself is worth checking on its own comparison page, and every claim about ZoomInfo on that same page is Cognism's characterization, not something pulled from ZoomInfo's site. A few independent reviews describe Cognism selling through annual contracts too, not exclusively monthly ones, so confirm the current contract terms directly with sales rather than assuming the comparison page reflects the deal you would actually get.

What ZoomInfo actually publishes about its own data

ZoomInfo's current business database page states 410M+ contact profiles and 203M+ company records. That is the number to use if you want ZoomInfo's own current claim about its own database size, and it is worth checking the live page yourself since both vendors update these figures as they grow. ZoomInfo does not publish a self-reported accuracy percentage as prominently as Cognism does on its comparison pages, leaning instead on database size, org-chart depth and intent-data coverage as its main pitch.

ZoomInfo is a US-headquartered, publicly traded company, and its coverage is strongest for US and North American contacts. Teams selling primarily into Europe consistently report thinner, staler records the further ZoomInfo's data reaches outside North America, which is the gap Cognism was built to fill.

Should you trust the 83% vs 85% accuracy stat going around?

If you search for an independent-sounding comparison of the two, you will run into a figure like "Cognism 83%, ZoomInfo 85% email accuracy" repeated across several sites. I traced that number back. It comes from a data-cleaning vendor's own comparison blog post, a company that sells an alternative to both Cognism and ZoomInfo, and the post discloses no sample size, no methodology, no date range and no test dataset. The same page also states that "neither consistently breaks 85% email accuracy," which is a reasonable-sounding line but not a documented finding.

That does not make the 83% vs 85% split wrong. It makes it unverifiable, and it means you should not repeat it to a client or a boss as a researched fact, since you cannot point to the underlying test if someone asks. This is the same pattern behind several vendor stats I have already traced for this blog: a specific-sounding number spreads across SEO blogs faster than anyone checks where it actually came from.

Does Diamond Data actually deliver?

Cognism's mobile numbers, branded Diamond Data, are collected differently from a standard scraped or algorithmically inferred number: a human researcher calls the number and confirms it reaches the named contact before it is added to the database. That mechanism is real and it is Cognism's own described process, not a marketing abstraction. Where sources disagree is the exact accuracy percentage attached to that subset, since different pages cite different figures for it. Rather than repeat a number I cannot pin to one disclosed test, the more useful fact is the mechanism itself: human-verified calling is a materially different (and more expensive to run) process than most databases use, and it is the reason Cognism can charge for it as a distinct tier.

If your outbound leans on calling as a primary channel, ask Cognism directly for its current published accuracy figure for Diamond Data specifically, not the blended database average, since that is the number that will actually predict your connect rate.

Which one is safer for GDPR and Do Not Call compliance?

This is the clearest, least disputed difference between the two. Cognism was built with European compliance as a first-class feature: Do Not Call and suppression list checks across the UK and a named set of European countries, consent tracking, and positioning aimed squarely at teams that call into the EU and UK under GDPR and national telemarketing rules. ZoomInfo meets standard compliance requirements but was not purpose-built around European calling restrictions the way Cognism was.

If your outbound motion includes calling into Europe, this is less a comparison of two similar products and more a question of whether the tool you pick was designed for the regulatory environment you are calling into.

Which one is cheaper, and which contract fits your team?

Neither vendor publishes pricing publicly, and both sell through a sales-led process for anything beyond a trial. Check current pricing directly with each before you budget anything, since packaging on both sides changes often enough that any number printed in an article is approximate within a quarter. What you can compare without a quote is the contract shape: ZoomInfo is consistently described as an annual, seat-minimum commitment sold through a sales team. Cognism's own page markets rolling monthly subscriptions, though confirm this directly, since independent reviews describe Cognism running annual deals as well depending on the plan.

The practical filter: if your team's data needs are still moving, a monthly or flexible option reduces the cost of picking wrong. If your data needs are stable and you would rather have a fixed, budgeted annual line item, the contract length itself is not a real downside.

Side by side

When Cognism is the right call

Cognism earns its cost when your motion depends on calling into Europe and the UK, when GDPR and national Do Not Call compliance is a real operating risk rather than a checkbox, and when phone-verified mobile numbers would meaningfully lift your connect rate over a standard enrichment tool.

When ZoomInfo is the right call

ZoomInfo earns its cost when your ICP is squarely North American, when you need org-chart and intent-data depth for enterprise account targeting, and when a bigger, US-weighted database matters more to your list-building than phone-verified mobiles or European compliance tooling.

How I'd verify this on your own list before signing anything

The mistake I see most often when I take over a data stack is a team that picked based on a comparison page, either vendor's, and never checked the result against their actual target accounts. Pull 50 to 100 of your real target accounts, run them through both vendors' trials or demos, and count matches yourself: email match rate, mobile match rate if calling matters to you, and how current the records look for the specific country your prospects sit in. That thirty-minute check tells you more about your outcome than any accuracy percentage either vendor, or a third party comparing them, has published.

This is the same check I run before recommending a data vendor to a client: the tool that wins the sales call is not always the tool that wins on the client's actual list, and the gap only shows up once you test it on accounts that look like the ones you are actually going to prospect.

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