Rate Limits

VerifNow enforces quotas per billing period and concurrent request limits to ensure fair usage and API stability. This guide explains the limits for each plan and how to handle them.

Plans & limits

How quotas work

• FREE plan: once you reach 500 validations in your billing period, subsequent requests are blocked with a 429 response.
• Paid plans (STARTER, GROWTH, PRO): requests above the included quota are not blocked. Instead, they are billed per unit at the end of the billing period.
• Quota reset: quotas reset at the start of each billing period. The billing period is tied to your subscription start date — for example, if your subscription started on the 4th, quotas reset every 4th of the month for a monthly subscription.

Limits are per API key. If you have multiple keys, each key shares your account quota.

Concurrent request limits

Each plan has a maximum number of simultaneous (concurrent) requests that can be in-flight at the same time. If you exceed this limit, the API returns a 429 Too Many Requests response — regardless of your plan.

For service protection, non-PRO plans (FREE, STARTER, GROWTH) are also subject to shared per-server concurrency controls. This means a request from a non-PRO plan can occasionally receive a 429 even if it is the only request currently in flight for that API key, or even if you are still within your plan’s documented concurrent request limit.

API key limits

Each plan has a maximum number of active API keys you can have at the same time:

If you need more API keys, consider upgrading your plan at app.verifnow.io .

Rate limit headers

Every API response includes headers so you can monitor your current usage:

HTTP/2 200
X-RateLimit-Limit: 500
X-RateLimit-Remaining: 413
X-RateLimit-Reset: 1705315200

When you hit the quota (FREE plan)

If you are on the FREE plan and exceed your quota, the API returns 429 Too Many Requests:

{
  "error": {
    "code": "quota_exceeded",
    "message": "Rate limit exceeded. Please upgrade your plan or try again later.",
    "status": 429
  }
}

When you exceed concurrent request limits (all plans)

If you send more simultaneous requests than your plan allows, the API returns 429 Too Many Requests with a concurrency_exceeded error code. The same status can also be returned for temporary server-side concurrency protection on non-PRO plans.

{
  "error": {
    "code": "concurrency_exceeded",
    "message": "Too many concurrent requests. Please retry later.",
    "status": 429
  }
}

Overage on paid plans

On paid plans (STARTER, GROWTH, PRO), requests above the included quota are allowed and will be billed at the per-unit rate at the end of the billing period.

HTTP/2 200
X-RateLimit-Limit: 10000
X-RateLimit-Remaining: 0
X-Quota-Overage: true

Reading rate limit headers

JavaScript

async function validateEmailWithQuotaCheck(email: string) {
  const response = await fetch('https://api.verifnow.io/api/v1/validate/email', {
    method: 'POST',
    headers: {
      'X-API-KEY': process.env.VERIFNOW_API_KEY!,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({ value: email }),
  })
 
  // Log quota info
  const remaining = response.headers.get('X-RateLimit-Remaining')
  const resetAt = response.headers.get('X-RateLimit-Reset')
  console.log(`Quota: ${remaining} validations remaining, resets at ${new Date(Number(resetAt) * 1000).toISOString()}`)
 
  if (response.status === 429) {
    const retryAfter = response.headers.get('Retry-After') ?? '5'
    throw new Error(`Request rejected because of quota or concurrency limits. Retry in ${retryAfter} seconds.`)
  }
 
  return response.json()
}

Proactive quota monitoring

Use this pattern to monitor your quota usage and alert when you’re running low:

class VerifNowClient {
  private remaining = Infinity
  private resetAt = 0
  private readonly apiKey: string
 
  constructor(apiKey: string) {
    this.apiKey = apiKey
  }
 
  async validate(email: string) {
    // Warn if we're running low on quota
    if (this.remaining < 50 && this.remaining > 0) {
      console.warn(`⚠️ Low quota: only ${this.remaining} validations remaining`)
    }
 
    const response = await fetch('https://api.verifnow.io/api/v1/validate/email', {
      method: 'POST',
      headers: {
        'X-API-KEY': this.apiKey,
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({ value: email }),
    })
 
    // Update local state from headers
    this.remaining = Number(response.headers.get('X-RateLimit-Remaining') ?? Infinity)
    this.resetAt = Number(response.headers.get('X-RateLimit-Reset') ?? 0)
 
    if (!response.ok) {
      throw new Error(`API error: ${response.status}`)
    }
 
    return response.json()
  }
}

Best practices

1. Monitor X-RateLimit-Remaining in every response — don’t wait for a 429 to find out
2. Implement exponential backoff — especially for 429 responses caused by concurrency or temporary server-side protection on non-PRO plans. See Error Handling
3. Cache results — if you’ve already validated an email recently, reuse the result
4. Upgrade your plan if you consistently exceed your quota — visit app.verifnow.io 
5. Track your usage in the dashboard  under Usage & Billing

Quota reset schedule

Quotas are reset at the start of each billing period, aligned with your subscription start date:

• Monthly subscription started on the 4th: quota resets on the 4th of each month
• Monthly subscription started on the 15th: quota resets on the 15th of each month

This is different from a calendar-month reset. Check the X-RateLimit-Reset header or your dashboard for the exact reset date.