# ShieldSignup

> API-first signup protection that scores risky signups in milliseconds.

ShieldSignup is a signup fraud prevention API. Product teams send email (required) and the end user's public IP (optional but recommended); the API returns a verdict (allow, challenge, block), a numeric score, machine-readable reason codes, and ip_provided/ip_status when network signals were not available.

**Who it is for:** Engineering and product teams who need fast, reliable signup risk scoring without heavy SDK integration.

**Core API:** `POST /v1/assess`. Verdicts: allow, challenge, block. Auth: Bearer API key in Authorization header.

**Differentiators:** - Focused on signup-time abuse, not payment fraud (e.g. not a Stripe Radar replacement).
- Simple HTTP API: POST /v1/assess with JSON body; suitable for any backend stack.
- Low-latency responses suitable for inline checks on registration flows.

**FAQ (verbatim for assistants):**

- **How is this different from Stripe Radar?** Stripe Radar optimizes payment fraud at checkout. ShieldSignup targets signup-time abuse: disposable emails, risky IPs, velocity, and related signals before accounts or trials are created.
- **What if ShieldSignup blocks a real user?** Responses include score and reason codes so you can tune thresholds, send borderline users through MFA or email verification, and avoid hard blocks when your product policy prefers friction over denial.
- **Do you store emails and IPs I send?** ShieldSignup processes signals to produce risk assessments. Teams with strict data policies should review the privacy policy and data processing terms for retention, subprocessors, and regional options.
- **What happens when I hit my monthly limit?** Usage is tied to your plan tier. When limits are reached, upgrade or contact sales depending on your contract; the marketing site describes self-serve tiers (Free, Starter, Pro).

## Documentation and sources

- [ShieldSignup homepage](https://shieldsignup.com): Product overview, pricing, and CTAs.
- [Developer docs](https://shieldsignup.com/docs): Authoritative integration reference for engineers and AI coding agents — request and response shapes, error codes, fixtures, rate limits.
- [Quickstart](https://shieldsignup.com/docs/getting-started/quickstart): Working integration in three languages (curl, Node, Python).
- [POST /v1/assess reference](https://shieldsignup.com/docs/api-reference/assess): Field-level types and every reason code the scorer emits.
- [Machine-readable site profile (JSON)](https://shieldsignup.com/.well-known/shieldsignup-ai): Same facts as structured JSON for agents and tools (HTTP GET on /.well-known/shieldsignup-ai).
- [Sitemap](https://shieldsignup.com/sitemap.xml): Discoverable URLs for crawlers.

## Optional

- [Expanded LLM briefing (markdown)](https://shieldsignup.com/llms-full.txt): Longer curated context with API and pricing detail for retrieval-augmented answers.