Quickstart

Make your first request in under a minute.

Every FILTER account gets a live API key and 100 free credits on signup — no card required. Once you have a key, verifying a number is a single request.

1. Make a request

curl -X POST https://api.usefilter.io/api/v1/filter \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"phone": "+919876543210", "source": "website"}'

2. Read the response

You'll get back one of three states: CONNECTED, ABSENT, or UNDETERMINED — never a raw provider error, and never our upstream provider's field names. See the API reference for the full shape.

{
  "country": "IN",
  "valid": true,
  "status": "CONNECTED",
  "carrier": "Jio",
  "line_type": "MOBILE",
  "is_ported": false
}

3. Check your balance any time

curl https://api.usefilter.io/api/v1/balance \
  -H "Authorization: Bearer YOUR_API_KEY"

That's the whole integration. No SDK to install, no webhook to configure for single lookups.