> ## Documentation Index > Fetch the complete documentation index at: https://technologychecker.io/docs/llms.txt > Use this file to discover all available pages before exploring further. # Category whitespace API > Find domains that run a qualifying anchor technology but no tool at all in a target category — greenfield prospecting, the inverse of adoption. Costs 1 credit. ## Frequently asked questions Domains that visibly have not bought yet: they run an anchor technology you can qualify on, and run nothing at all in the category you sell into. "Shopify stores with no email marketing tool" is the canonical query. Whitespace is a current-state signal about presence and absence, not a transition between two states. There is nothing to look back over. This also means it works from day one and needs no monitoring-window maturity, unlike adoption and churn. Very. Any active detection of a technology in the missing category disqualifies the domain, even a flaky one, and the check runs at domain level rather than per subdomain — if the company has the tool anywhere, they are excluded. We would rather drop a real prospect than surface a false gap. The anchor side is the opposite: it is gated by `min_confidence` so the qualifying presence is trustworthy. Use `limit` with `offset`. Whitespace matches routinely run into the millions and results are ordered alphabetically by domain, so paging is stable within one corpus generation. This is the only signal endpoint with offset paging — the transition signals are recency-ordered, where the newest rows are the product. An unqualified "every domain without category C" query is rejected with a 400. It would return most of the internet and would not be a prospect list. The anchor is what makes the result actionable. ## OpenAPI ````yaml GET /v1/signals/whitespace openapi: 3.1.0 info: title: TechnologyChecker API description: >- Discover technology stacks, track market trends, and enrich data with company intelligence. version: 1.0.0 contact: name: TechnologyChecker Support email: support@technologychecker.io url: https://technologychecker.io servers: - url: https://api.technologychecker.io description: Production security: - bearerAuth: [] tags: - name: Domain technologies description: Look up technologies detected on any domain - name: Technology data description: Search, look up, and get details on tracked technologies - name: Market intelligence description: Technology stats, trends, and market share - name: Company data description: Firmographic and company intelligence - name: Live detection description: Real-time technology detection with browser rendering - name: Signals description: >- Intent signals derived from technology state transitions: who adopted, who churned, who switched, and who has a gap in their stack. - name: Alerts description: >- Saved signal queries delivered to your webhook. Every signal you can query, you can subscribe to. - name: Audiences description: >- Saved groups of domains — uploaded lists or computed recipes — that you can profile, slice and monitor. - name: Lead lists description: >- Build and export targeted domain lists combining technology detection with company data. paths: /v1/signals/whitespace: get: tags: - Signals summary: Category whitespace API description: >- Greenfield prospecting: domains that **have** a qualifying anchor technology but run **no tool at all** in a target category. The structural inverse of adoption — not who just bought, but who visibly has not yet. This is a current-state signal rather than a transition, so there is no `window` parameter. It is also the cheapest signal to run, and supports offset pagination because matches routinely run into the millions. Costs 1 credit. operationId: getCategoryWhitespace parameters: - name: technology_id in: query required: false description: >- Scope by BuiltWith technology id. Provide exactly one of `technology_id`, `technology` or `category_id`. schema: type: integer example: 2184 - name: technology in: query required: false description: Scope by exact technology name. The technology must be detectable. schema: type: string example: Shopify - name: category_id in: query required: false description: >- Scope by category — fans out to every detectable technology whose *primary* category is this one. schema: type: integer example: 202 - name: missing_category_id in: query required: false description: >- **Required.** The category the domain must run no tool in. Must differ from the anchor category. schema: type: integer example: 202 - name: min_confidence in: query required: false description: >- Minimum `detection_rate` gating the *anchor* presence. The gap side counts any active detection, which is deliberately conservative. schema: type: number format: float default: 0.5 - name: limit in: query required: false description: Rows returned. Clamped to 1–1000. schema: type: integer default: 100 minimum: 1 maximum: 1000 - name: offset in: query required: false description: >- Pagination offset, clamped to 0–1,000,000. Results are ordered alphabetically by domain, so paging is stable within one corpus generation. schema: type: integer default: 0 - $ref: '#/components/parameters/FirmoCountry' - $ref: '#/components/parameters/FirmoCity' - $ref: '#/components/parameters/FirmoState' - $ref: '#/components/parameters/FirmoIndustry' - $ref: '#/components/parameters/FirmoIndustryCode' - $ref: '#/components/parameters/FirmoEmployees' - $ref: '#/components/parameters/FirmoCompanyType' - $ref: '#/components/parameters/FirmoFoundedMin' - $ref: '#/components/parameters/FirmoFoundedMax' - $ref: '#/components/parameters/FirmoCompany' - $ref: '#/components/parameters/WebHasEmail' - $ref: '#/components/parameters/WebHasPhone' - $ref: '#/components/parameters/WebSocial' - $ref: '#/components/parameters/WebLanguage' - $ref: '#/components/parameters/WebCountry' - $ref: '#/components/parameters/SegmentId' responses: '200': description: Domains with the anchor and no tool in the target category content: application/json: schema: type: object properties: success: type: boolean example: true data: type: object properties: signal: type: object properties: type: type: string example: whitespace verb: type: string example: lacks anchor: type: object description: What the domains have. properties: kind: type: string enum: - technology - category technology: type: object nullable: true category: type: object nullable: true missing_category: type: object description: What the domains lack. properties: id: type: integer example: 202 name: type: string example: Email Marketing technology_count: type: integer example: 37 min_confidence: type: number format: float example: 0.5 total_sites: type: integer nullable: true description: >- Corpus-wide count of whitespace domains, not capped by `limit`. example: 911747 domains: type: array items: type: object properties: domain: type: string example: 0-5.fr company: $ref: '#/components/schemas/CompanyCard' firmographics: $ref: '#/components/schemas/FirmographicsEcho' limit: type: integer example: 100 offset: type: integer example: 0 count: type: integer example: 1 '400': $ref: '#/components/responses/BadRequest' '401': $ref: '#/components/responses/Unauthorized' '402': $ref: '#/components/responses/PaymentRequired' '404': $ref: '#/components/responses/NotFound' '429': $ref: '#/components/responses/RateLimited' components: parameters: FirmoCountry: name: country in: query required: false description: Filter to companies in this country (case-insensitive). schema: type: string example: united states FirmoCity: name: city in: query required: false description: Filter to companies in this city (case-insensitive). schema: type: string FirmoState: name: state in: query required: false description: Filter to companies in this state or region (case-insensitive). schema: type: string FirmoIndustry: name: industry in: query required: false description: Filter to companies in this industry (case-insensitive). schema: type: string example: retail FirmoIndustryCode: name: industry_code in: query required: false description: Filter by exact LinkedIn industry code. schema: type: integer FirmoEmployees: name: employees in: query required: false description: >- Filter by exact LinkedIn employee band. Unknown bands are rejected with `INVALID_EMPLOYEE_BAND` and the allowed list. schema: type: string example: 51-200 FirmoCompanyType: name: company_type in: query required: false description: Filter by exact company type. schema: type: string example: Privately Held FirmoFoundedMin: name: founded_min in: query required: false description: Only companies founded in or after this year. schema: type: integer minimum: 1800 maximum: 2025 FirmoFoundedMax: name: founded_max in: query required: false description: Only companies founded in or before this year. schema: type: integer minimum: 1800 maximum: 2025 FirmoCompany: name: company in: query required: false description: >- Set to `true` to attach the company card without filtering results (enrich-only mode). schema: type: boolean example: true WebHasEmail: name: has_email in: query required: false description: >- Filter to domains where the crawler found (or did not find) an email address. `false` is a real filter, not a no-op. schema: type: boolean WebHasPhone: name: has_phone in: query required: false description: >- Filter to domains where the crawler found (or did not find) a phone number. schema: type: boolean WebSocial: name: social in: query required: false description: Filter to domains publishing a profile on this platform. schema: type: string enum: - linkedin - x - facebook - instagram - youtube - github - tiktok - discord - reddit - crunchbase - slack example: instagram WebLanguage: name: language in: query required: false description: Filter by the site's primary language. schema: type: string example: de WebCountry: name: web_country in: query required: false description: >- Filter by the country the site declares in its schema.org markup. Accepts ISO-2, English name or common variants. schema: type: string example: USA SegmentId: name: segment_id in: query required: false description: >- Apply a saved audience instead of inline filters. Filter audiences replay their firmographic predicates; list audiences restrict rows to their member domains. Mutually exclusive with inline firmographic parameters. schema: type: string example: seg_8f3a2c1b schemas: CompanyCard: type: object nullable: true description: >- LinkedIn company card attached when firmographic enrichment is on. `null` when the domain has no LinkedIn match (roughly 23–30% of technology domains match). properties: name: type: string example: Ghostcircusapparel industry: type: string example: Retail Apparel and Fashion industry_code: type: integer example: 18 employees: type: string example: 51-200 country: type: string example: united states city: type: string nullable: true state: type: string nullable: true founded: type: integer nullable: true example: 2015 company_type: type: string example: Privately Held FirmographicsEcho: type: object description: Echo of the firmographic predicates that took effect on this request. properties: applied: type: object additionalProperties: true example: country: united states employees: 51-200 filtered: type: boolean description: >- `true` when results were narrowed to matched companies; `false` for enrich-only (`company=true`). example: true note: type: string example: >- Results are limited to domains with a matched LinkedIn company that passes these filters (~23–30% of tech-domains have a company match). ApiError: type: object properties: success: type: boolean example: false error: type: object properties: code: type: string example: UNAUTHORIZED message: type: string example: Missing or invalid API key responses: BadRequest: description: Invalid or missing parameters content: application/json: schema: $ref: '#/components/schemas/ApiError' example: success: false error: code: VALIDATION_ERROR message: >- Provide exactly one scope: technology_id, technology or category_id. Unauthorized: description: Missing or invalid API key content: application/json: schema: $ref: '#/components/schemas/ApiError' PaymentRequired: description: Not enough credits, or the plan does not include this feature content: application/json: schema: $ref: '#/components/schemas/ApiError' example: success: false error: code: INSUFFICIENT_CREDITS message: Insufficient credits for this request. details: required: 1 available: 0 NotFound: description: Resource not found content: application/json: schema: $ref: '#/components/schemas/ApiError' RateLimited: description: Rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/ApiError' securitySchemes: bearerAuth: type: http scheme: bearer description: >- API key in format `tapi_live_[32-char]` (live) or `tapi_test_[32-char]` (test) ````