Every fraud check your signup and billing flows need

Email validation, IP intelligence, geolocation, memory of who it has seen, and Stripe chargeback prevention. One API call, one risk score, under 200ms.

Last updated: October 2026

Catch bad email addresses

RFC-compliant syntax checking, domain verification, disposable email detection, and custom blocklists.

Block bad IP addresses

Detect VPNs, proxies, Tor nodes, and problematic ISPs. Real-time geolocation with location matching.

Remember signups and logins

Tell Fidro what is happening and who it is. It counts repeat activity per IP, subnet, email pattern and user, and flags signup bursts, shared IPs and impossible travel.

Prevent chargebacks

Score every Stripe payment as it completes and refund the risky ones before they become disputes, fees, and processor scrutiny.

Score each action

Weighted 0 to 100 score with an allow, challenge or block recommendation and a human-readable message naming every reason.

Build your own blocklists

Manage your own blocklists with severity levels. Share entries across accounts or keep them private.

Built for developers

REST API with copy-paste code samples. 5 lines of code and you're live in minutes, not sprint cycles.

Ask it from your AI assistant

An MCP server exposes validation, lookups and blocklists to Claude, Cursor and any MCP client, so "is this signup risky?" is a complete request.

Audit every decision

Every call is logged with its score, checks, event and anomalies, so you can see why a signup was challenged weeks later.

$362B+

Projected merchant losses to online payment fraud between 2023 and 2028. (Source: Juniper Research)

1 in 8

Form signups use a disposable email address. See the 2026 data. (Source: EmailListVerify, 2026)

Email Validation

Catch invalid, disposable, and blocklisted addresses before they ever reach your database. Try it live with the free email checker.

  • RFC-compliant syntax validation
  • MX and DNS record verification
  • Disposable email detection
  • Custom email and domain blocklists 
POST /api/validate
{
  "email": "user@example.com"
}

Response:
{
  "risk_score": 15,
  "risk_message": "LOW RISK",
  "data": {
    "checks": {
      "invalid_email": false,
      "disposable_email": false
    }
  }
}
POST /api/validate
{
  "ip": "203.0.113.7",
  "country_code": "US"
}

Response:
{
  "risk_score": 45,
  "risk_message": "MODERATE RISK - VPN detected,
                   location mismatch",
  "data": {
    "checks": {
      "vpn": true,
      "proxy": false,
      "tor": false,
      "location_match": false
    },
    "location": {
      "country_code": "NL",
      "city": "Amsterdam"
    }
  }
}

IP Analysis

Know when a signup is hiding behind a VPN, proxy, Tor, or a datacenter before you trust it. Test any address with the VPN detector.

  • VPN, proxy, and Tor detection
  • Real-time geolocation lookup
  • Location matching and verification
  • ISP reputation checking

Velocity and Anomalies

A clean address from a clean IP is still a problem when it is the fifth signup from that IP this hour. Add event and user_id to the call and Fidro keeps the history, counts the pattern and raises the score before the account exists. On every plan. Read the velocity guide.

  • Signup bursts from one IP or one /24 subnet
  • Email pattern bursts (plus-tags, dots and trailing digits stripped)
  • Many users behind one IP
  • New country for a known user, and impossible travel
  • Counts and anomalies in every response and in the audit log 
POST /api/validate
{ "email": "c.lark@example.com", "ip": "203.0.113.1", "event": "signup" }

{
  "risk_score": 40,
  "recommendation": "challenge",
  "message": "No risk factors detected. Velocity: ip signup burst.",
  "data": {
    "velocity": { "ip_signups_1h": 3, "subnet_signups_1h": 3 },
    "anomalies": [
      {
        "code": "ip_signup_burst",
        "severity": "high",
        "detail": "3 signups from 203.0.113.1 in the last hour."
      }
    ]
  }
}

Stripe Chargeback Prevention

Score every completed payment and refund the risky ones before they turn into disputes that count against Visa's 2026 VAMP thresholds.

  • Real-time transaction analysis
  • 25+ risk factors evaluated
  • Same card detected across multiple accounts
  • Intelligent refund recommendations
  • Complete audit trail 
Webhook: payment_intent.succeeded
{
  "risk_score": 78,
  "recommendation": "refund",
  "risk_message": "HIGH RISK - Multiple red flags"
}

Frequently Asked Questions

What types of fraud does Fidro detect?

Fidro detects disposable and temporary email addresses, VPN and proxy usage, Tor exit nodes, datacenter IPs, suspicious ISPs, geolocation mismatches, signup bursts, shared IPs, impossible travel, and high-risk Stripe transactions. All checks run in a single API call and return a unified risk score.

How does Fidro's email validation work?

Fidro performs RFC-compliant syntax validation, MX and DNS record verification, disposable email domain detection against a database of 50,000+ known domains, and custom blocklist matching. Results are returned in under 200ms.

How does Fidro prevent Stripe chargebacks?

Fidro evaluates 25+ risk factors on each Stripe transaction including email reputation, IP intelligence, geolocation matching, transaction velocity, and card fingerprint tracking that catches the same card used across multiple customer accounts. High-risk transactions receive an automatic refund recommendation before a chargeback can be filed.

How does Fidro detect signup bursts and impossible travel?

Send an event such as signup or login, and optionally a user_id, with each /validate call. Fidro records the call and counts related activity over the last hour, day and month: signups from the same IP and /24 subnet, addresses that reduce to the same pattern once plus-tags and dots are removed, distinct users behind one IP, and the IPs and countries each user appears from. Six rules fire on those counts, including ip_signup_burst, email_pattern_burst and impossible_travel, each adding to the score and the high-severity ones forcing at least a challenge recommendation. It is included on every plan.

How fast is Fidro's API?

Fidro's API responds in under 200ms on average, making it suitable for real-time validation during signup flows and payment processing without adding noticeable latency.

Start catching bad signups in the next 5 minutes

Create your account, grab your API key, and send your first request. Free plan with 200 validations/month. No credit card. Cancel anytime.

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