# Method (v1.0, 2026-09-27)

## Sample

One homepage per company in the Y Combinator directory. A rendered record
wins; a domain with no usable rendered record is counted from its plain
record. This is the same denominator as the Installmap report on visitor
identification tags (v1.1).

| Step | Rows |
| --- | ---: |
| YC directory rows | 6,133 |
| Scored homepages (denominator) | 5,386 |
| of which rendered | 5,242 |
| of which plain only | 144 |
| No usable record (dead or blocked site) | 747 |
| Crunchbase record matched by exact domain | 4,508 |
| Funding total known | 3,177 |
| Last round type known | 4,366 |
| Semrush monthly visits known | 3,986 |
| Month-on-month change known | 3,019 |

117 domains had more than one Crunchbase record; the record with the most
funding rounds was kept.

## What counts as a hit

A homepage counts when it loads a fingerprinted script from one of the 30
vendors in the Visitor Identification & ABM category. Each rule matches the
hostnames the vendor's own snippet loads. A vendor named in a consent banner's
provider list, a Content-Security-Policy header or an opt-out link does not
count. HubSpot's built-in reverse-IP lookup and the LinkedIn Insight Tag are
not counted.

Name level (tries to match the visitor to a name and email address): RB2B,
Warmly, Vector, Retention.com, Customers.ai, Opensend, Hyros. Company level
(resolves the visitor's IP address to an employer): the other 23.

## Joined fields

- Money raised: Crunchbase funding total, which counts every round Crunchbase
  lists, debt rounds included. Bands: under $1M, $1M-5M, $5M-20M, $20M-50M,
  $50M-100M, $100M or more; no figure is "unknown".
- Last round: Crunchbase last_funding_type. Series D to J are pooled as
  "Series D or later". Series unknown, grants, debt, convertible notes and
  other types are pooled as "other round type".
- Months since the last raise: counted from Crunchbase last_funding_at to
  2026-09-18, the latest round date in the snapshot.
- Traffic: Semrush monthly visits and their month-on-month change, as carried
  in the Crunchbase record.
- Hiring and top company: the isHiring and top_company flags in the YC company
  directory, records from 2026-08-25.
- Status, team size, batch and industry: the YC company directory. A team size
  of 0 is treated as unknown (188 homepages).

## Odds ratios

Logistic regression fitted by iteratively reweighted least squares, 95% Wald
intervals. Terms: B2B industry, log10 of monthly visits, team size (1-10,
11-50, 51-200, over 200), batch (2016 or earlier, 2017-20, 2021-22, 2023,
2024, 2025 or later), last round (seed or pre-seed, Series A or later, other
or none), months since the last raise (under 18, 18-36, 36 or more, unknown),
hiring, YC status active. The restricted model covers the 2,085 homepages with
1,000 or more monthly visits, a known month-on-month change and a known team
size, and adds the change band. The full model covers the 5,198 homepages with
a known team size and adds an indicator for missing visits. The script is
`research/drafts/yc-best-funded-visitor-identification.build.py`.

## Re-render check

Every tagger with $100M or more raised or a YC top-company flag, 58 homepages,
was rendered again on 2026-09-27. 49 loaded every vendor recorded on
2026-09-04, 4 loaded some of them, 1 loaded a different vendor only and 4
loaded none. A company is named in the report only with the vendors seen on
both fetches.

## Limitations

- Homepage only. A script on a pricing page, a demo form or behind a login is
  missed, so every share is a floor.
- One crawl for the shares. The re-render of 58 homepages three weeks later
  found the same vendors on 49.
- Crunchbase funding totals and Semrush visits are third-party estimates.
  Funding bands exclude the 2,209 homepages with no funding figure.
- The month-on-month traffic change covers a single month.
- YC team size and hiring are self-reported to YC.
- Companies whose site no longer loads are outside the denominator.