# Newsletter signup forms and their providers across four company lists

Two kinds of row, marked by `row_type`. A `metric` row carries one aggregate
with the base it was computed on. A `domain` row carries one company whose
homepage carried a newsletter signup form.

## Columns

- `row_type`: `metric` or `domain`.
- `group`: `inc5000_2026`, `yc`, `fortune500`, `unicorns` or
  `all four groups`.
- `segment`: `all` for a whole-group figure, otherwise the cut and the
  segment, such as `industry: Consumer Products`, `batch year block: 2022` or
  `rank band: 1-100`. Empty on domain rows.
- `metric`: on a metric row, the figure. `base` is the number of companies
  counted. `n1_provider_form_count`, `n2_email_capture_count`,
  `n3_newsletter_link_count`, `newsletter_strict_count` and
  `newsletter_any_count` are domain counts, and the matching `_pct` metrics
  are those counts as a percentage of `base`. `n1_provider_<name>` counts the
  domains carrying that provider's form. `Substack_form_count`,
  `Substack_link_count` and `Substack_either_count`, and the same three for
  beehiiv, split the platform into a form on the page, a link to the platform,
  and the union. `truncated_records_count` counts the pages that hit the
  storage cap. Empty on domain rows.
- `value`: the figure. A count of one to four prints `<5`; a share on a base
  under 20 prints `n/a`.
- `base`: the denominator for that row.
- `domain`, `name`: the company, on domain rows.
- `rank`: Fortune 500 rank, on Fortune 500 domain rows.
- `industry`: Inc 5000 industry, on Inc 5000 domain rows.
- `batch`: Y Combinator batch year, on YC domain rows.
- `n1_providers`: the named email providers whose form sits on the homepage,
  pipe separated. Empty where the signup form belongs to no named provider.
- `n3_hosts`: the hosts of the newsletter links found, pipe separated, up to
  five per domain.
- `n2_word`: the newsletter word that made the form count.

Domain rows are the newsletter_strict positives: N1 or N2. A domain with a
newsletter link and no form (N3 only) is not a domain row here.

## Denominators

The base for every percentage is the companies in that group with a usable
archived homepage: an HTTP status under 400 and a non-empty body.

| Group | Base | Domains on the list |
| --- | ---: | ---: |
| Inc 5000 (2026) | 4,885 | 4,969 |
| Y Combinator | 5,386 | 6,133 |
| Fortune 500 | 472 | 500 |
| Unicorns | 1,000 | 1,111 |
| All four | 11,743 | 12,713 |

## Headline

Klaviyo's form sits on 109 Inc 5000 homepages and Mailchimp's on 91. On the Y
Combinator list Mailchimp leads with 53 against Klaviyo's 19, and on the
unicorn list Marketo leads with 16. No provider reaches five domains in the
Fortune 500.

## Licence

Data: CC BY 4.0, Installmap, 2026-09-04.
Source: Installmap, September 2026.