Companies Using Apollo.io

A disclosure before anything else: TechnologyChecker.io sells B2B company and technology data, which puts us in Apollo.io's neighbourhood. So read this as a data profile from a neighbour, and check the numbers rather than my adjectives. Our September 2026 crawl finds Apollo's website tracker on 28,074 domains, and 20,260 of them match a company record we can describe.

What the count measures, and what it misses

Apollo's core product is a contact database with sequencing and calling on top. A salesperson using it leaves no trace on their employer's website. What we can detect is the optional website tracker, a script from assets.apollo.io that, per Apollo's help centre, sets a first-party cookie and identifies visiting companies, or companies plus U.S.-based contacts if the customer turns that on.

Apollo's homepage says more than 600,000 companies use the product. Our 20,260 matched companies are about 3% of that. I don't read that as a contradiction. Most Apollo customers buy it for outbound and never wire up the inbound side. The signal is clean where it exists: when we loaded the 50 largest detection hosts in a browser, 44 of the 49 that loaded requested the tracker.

Sales Signal: A detection marks a company that has connected its website to its outbound workflow. That is a more committed Apollo user than a lone seat holder with the Chrome extension, and a better target for anything that sits between marketing and sales.

Growth trajectory: too early to call

We began detecting the tracker on 4 August 2026. The chart reads 19,426 domains in August and 28,074 in September, but August is a partial month and every domain in the base was first seen in the last two months, 21,224 in August and 6,665 in September. On top of that, the set of domains we crawl turns over every month. Any growth rate taken from these two points would be a statement about our detection, not about Apollo.

"The honest trend line for Apollo's tracker is two dots. I'd rather publish a clean baseline in September than a growth story that is our own ramp-up in disguise." - Mehmet Suleyman, CEO & Co-founder at TechnologyChecker.io

Sales Signal: Don't size a market off this chart yet. From November onward, a domain first seen after our August start is far more likely to be a new install, and that is the timing signal to watch.

Customer profile

This is a small-company base. 78.75% of matched companies have fewer than 51 employees, and 71.19% were founded in 2010 or later, 30.97% in the 2020s alone. Only 214 have more than 1,000 staff. That fits a product with a free plan: a founder or first sales hire can start without procurement.

The larger names are mostly services exporters: R Systems, iSoftStone, Movate, Ciklum, Centific. There are exceptions worth knowing about. Insider Inc. runs the tracker on live.businessinsider.com, Plug Power on its main site, and Hack The Box on its academy subdomain rather than its homepage.

Sales Signal: The buyer here is usually a founder or a head of sales at a sub-50-person tech or services firm, not a revenue operations team. Pitch time saved, not governance.

Industry and geographic concentration

Software Development (15.46%), IT Services and IT Consulting (12.32%), Technology, Information and Internet (6.85%) and Information Technology & Services (2.72%) together make up 37.35% of matched companies. Agencies add 12.77% across advertising, marketing and design services. Half the base sells software, services or campaigns to other businesses.

The United States leads with 9,315 matched companies, 4.7 times the UK's 1,976. India is third with 1,253, ahead of Canada and Australia, and the Indian companies in the list are mostly IT exporters selling into those two markets.

Sales Signal: India is third, ahead of Canada and Australia. A sales-tool vendor that treats it as an afterthought is ignoring 1,253 of the companies on this list.

Why there is no migration table

We checked for switching between Apollo and ZoomInfo, Leadfeeder, 6sense, Warmly, Clearbit, Koala and HubSpot. Every pair failed. Between 77% and 92% of the domains that ran both still run both, and each rival is more common on sites that kept Apollo than on sites that dropped it, the opposite of what a replacement looks like. 2,374 domains have dropped the tracker since August, but 62.4% of those were seen only once, so that figure is mostly detection flicker in a seven-week window.

"Apollo's tracker doesn't displace ZoomInfo or Leadfeeder on the sites we can see. Where two of these tags meet on one site, they usually stay together." - Mehmet Suleyman, CEO & Co-founder at TechnologyChecker.io

Sales Signal: A site running Apollo plus another identification tag is paying twice for overlapping data. That is a consolidation conversation, whichever side you sell for.

Technology ecosystem

HubSpot is on 34.47% of Apollo domains and Salesforce on 3.44%, roughly ten to one. Paid social is common: the LinkedIn Insight Tag is on 36.32% and the Facebook Pixel on 33.58%. WordPress leads the website builders at 37.2%, with Webflow at 11.61%. Our HubSpot statistics report covers the other half of that pairing.

Sales Signal: Anything that syncs Apollo with HubSpot is selling into a third of this list. Salesforce-first products will find the tracker base thin.

G2 review signals

Apollo.io scores 4.7 out of 5 from 9,832 G2 reviews. Ease of use leads the praise with 1,587 mentions. Data quality leads the criticism once G2's two labels are combined: 889 mentions across inaccurate data and data inaccuracy, ahead of missing features at 559.

Our data lines up with the praise. A base that is 78.75% under 51 staff has no one to run a hard tool, so ease of use is what keeps it. The accuracy complaint is the price of a large self-serve database, and in a base this small there is rarely an operations person to clean records before they reach a sequence.

Sales Signal: Data verification and enrichment tools have a clear opening in this base. The complaint is public, frequent and specific.

Key takeaways

1. Coverage: 28,074 domains run Apollo's tracker; the 20,260 we match to companies are about 3% of the 600,000+ companies Apollo reports.

2. Growth phase: unknown. Detection began on 4 August 2026, and two readings are not a trend.

3. Core customer: a small software, IT services or agency business, founded after 2010, running HubSpot.

4. Competition: visitor-identification tags stack rather than replace each other.

5. Weak spot: data accuracy, with 889 G2 mentions.

Sales applications

Outreach angle: "You run Apollo's tracker next to HubSpot" is true for a third of this list and shows you checked their site.

Targeting: On TechnologyChecker.io, filter Apollo.io users by 11 to 200 employees and software or IT services. That is the segment with a sales team and the budget to add tools.

Competitive angle: Cross-filter Apollo users against ZoomInfo or Leadfeeder detections to find companies paying for overlapping visitor data.

All counts above come from TechnologyChecker.io's live crawl: 28,074 domains running Apollo.io's tracker, 20,260 matched to company records, refreshed monthly.