# subdomain-app

**Canonical:** https://apis.io/providers/subdomain-app/  
**Website:** https://subdomain.app/  
**APIs profiled:** 1

Subdomain API provides a free, no‑signup JSON API that returns the subdomains associated with any given domain. Leveraging one of the largest publicly available subdomain indexes, the service enables developers and security researchers to automate discovery, enrich threat intelligence, and integrate subdomain enumeration into CI/CD pipelines. The API is publicly accessible via HTTPS GET requests and returns results in a simple JSON array, making it easy to consume in scripts and applications.

## Kin Score — 23.1 / 100 (emerging)

Scored 2026-10-31 under rubric 0.25.0.

| Facet | Score |
|---|---|
| Discoverability | 66.1 |
| Contract Quality | 0.0 |
| Contract Governance | 65.5 |
| Operational Transparency | 18.9 |
| Developer Ergonomics | 0.0 |
| Access Clarity | 21.1 |

Regulatory layer — **Horizontal (data, software, accessibility, platform)**: 28.4 (matched via fallback).

## Agent readiness — 15.0 (agent-aware)

| Dimension | Value |
|---|---|
| Spec Presence | no |
| Agentic Access | unknown |
| Reversibility Documented | no |
| MCP Server | documented |
| Auth Clarity | no |
| Idempotency | no |
| Error Semantics | documented |
| OpenAPI Examples | no |
| Rate Limit Signal | documented |
| Event Surface Described | no |
| Agent Skills | no |
| Well Known Catalog | no |
| Consent Identity | no |
| Agent Card | no |
| Dry Run Mode | no |
| Delegated Identity | no |
| Protected Resource Metadata | no |
| Dynamic Client Registration | no |
| Agentic Commerce | no |
| Pagination Ratio | na |
| Operation Distinctiveness | na |

## APIs (1)

- **Subdomain API** — Find the subdomains of a domain name.

## Agentic access (1)

- **Subdomain App Agentic Access** — 1 operation

## Security (2)

- **Subdomain App Authentication** — 0 schemes
- **Subdomain App Domain Security** — TLSv1.3 · HSTS · DNSSEC · DMARC

## Plans (1)

- **Subdomain App Plans Pricing**

## Tags

Security, Subdomain, Discovery, API, Free

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Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/providers/subdomain-app/). Scores are computed from the provider's own public artifacts under a published rubric.