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GET
Find Similar Companies
Prefer POST /v1/companies/{company_identifier}/similar. This GET endpoint is deprecated. It still works and returns identical results, but POST is the recommended default: it takes filters as a JSON object and is not limited by URL length (required for large exclude.domains lists).

Overview

Lookalike Search returns companies ranked by similarity to a reference company. Pass a company domain or UUID. Result quality depends heavily on how representative the seed company is.

Example request

Key parameters

  • company_identifier (required): Company domain or UUID.
  • filters (optional): JSON string to narrow results.
  • offset (optional): Pagination offset.
  • limit (optional): Page size, up to 250 per request.
Lookalike uses the same filter format as semantic search. See Search Filters Reference.

Endpoint behavior

  • Ranking blends what a company does, who it sells to, firmographics, and traffic.
  • filters narrow the result set, but the seed company still determines what “similar” means.
  • Prefer a clear, representative company domain when possible. Use a UUID when you already have one from Extruct.
  • A single request returns at most 250 results. Page with offset to read deeper: paid plans (Starter, Pro) can reach up to 2,000 results per query; the free tier is capped at 25.

Success signal

A successful response returns results with company candidates. Reuse results[].domain or results[].id in follow-up workflows.

Common errors

401 Unauthorized

Check that your header is Authorization: Bearer ${EXTRUCT_API_TOKEN}.

404 Not Found

The reference company identifier is not present in the index. Try a known domain from semantic results (results[].domain) or a valid UUID.

422 Unprocessable Entity

Most often caused by malformed filters JSON. Validate before sending:

Authorizations

Authorization
string
header
required

Bearer authentication header of the form Bearer <token>, where <token> is your auth token.

Path Parameters

company_identifier
string
required

Reference company UUID or domain.

Query Parameters

filters
string | null

JSON string of SearchFilters. Supported keys only: include.size/country/city, exclude.size/country/city/domains, range.founded.min/max.

offset
integer | null
limit
integer | null

Response

Successful Response

Lookalike search response wrapper.

results
CompanySearchResult · object[]
required

Search results

request
LookalikeRequestInfo · object
required

Request parameters echo

reference_company
CompanySearchResult · object | null

Reference company for lookalike searches