Look up domains associated with an IP address or attribute tag via BuiltWith's Tags API.
What it does
The BuiltWith Tags endpoint (`/builtwith/tags`) lets you query BuiltWith's technology profiling database by IP address or attribute identifier. You supply a LOOKUP value — either an IP address (prefixed with "IP-") or an attribute string — and receive back the associated domain and technology tag data. This is useful for reverse-IP lookups, discovering which websites share hosting infrastructure, or finding domains linked by a common attribute across BuiltWith's index of 100M+ websites.
This endpoint is part of a broader BuiltWith suite exposed through the Locus MPP (Micropayment Protocol) gateway. Each call costs 55,000 base units of pathUSD (6 decimals), which works out to $0.055 per request, settled on Tempo L2. The payment intent is "charge", meaning each request is a one-shot micropayment. The endpoint accepts POST requests with a JSON body containing a required `LOOKUP` field.
Other endpoints in the same BuiltWith suite include domain tech-stack lookup, technology lists, domain relationships, company-to-URL resolution, product search, trends, trust signals, keywords, redirects, recommendations, and a cheaper free-summary tier. All are accessible at the same `builtwith.mpp.paywithlocus.com` host under different paths.
Capabilities
Use cases
- —Reverse-IP lookup to find all domains hosted on a given IP address
- —Discover domains sharing a common BuiltWith attribute or tag
- —Enrich threat-intelligence or security workflows with hosting infrastructure data
- —Competitive analysis by identifying co-hosted or related websites
- —Automated infrastructure mapping for sales prospecting
Fit
Best for
- —Security researchers performing reverse-IP reconnaissance
- —Sales and marketing teams mapping competitor infrastructure
- —Data enrichment pipelines needing IP-to-domain resolution
- —Agents that need per-call pay-as-you-go access to BuiltWith without a subscription
Not for
- —Full tech-stack profiling of a single domain (use the /builtwith/domain endpoint instead)
- —Bulk technology adoption trend analysis (use /builtwith/trends instead)
- —Users who need free access — every call costs $0.055
Quick start
curl -X POST https://builtwith.mpp.paywithlocus.com/builtwith/tags \
-H "Content-Type: application/json" \
-d '{"LOOKUP": "IP-93.184.216.34"}'Example
Request
{
"LOOKUP": "IP-93.184.216.34"
}Endpoint
Quality
The OpenAPI spec provides a clear request schema and pricing, but the probe did not capture a live 402 challenge on HEAD/GET (the endpoint requires POST). No response schema or example response is documented. Crawled pages all return 404 since only path-specific POST routes are valid.
Warnings
- —Probe used HEAD/GET which returned 404; the endpoint is POST-only per the OpenAPI spec, so liveness could not be confirmed via the probe.
- —No response schema or example response is provided in the OpenAPI spec.
- —Currency address 0x20c000000000000000000000b9537d11c60e8b50 is assumed to be pathUSD with 6 decimals based on the Tempo/Locus convention; if decimals differ, the stated price of $0.055 would be incorrect.
Citations
- —The /builtwith/tags endpoint accepts POST with a required LOOKUP field (IP address prefixed with 'IP-' or attribute).https://builtwith.mpp.paywithlocus.com
- —Each call costs 55,000 base units settled via Tempo L2 with intent 'charge'.https://builtwith.mpp.paywithlocus.com
- —BuiltWith covers 100M+ websites for technology profiling.https://builtwith.mpp.paywithlocus.com
- —API reference available at https://api.builtwith.com and LLM docs at https://beta.paywithlocus.com/mpp/builtwith.mdhttps://builtwith.mpp.paywithlocus.com