Rate Limits

To keep the service available for everyone, HTTP requests are rate-limited per IP (anonymous) or per client account (authenticated). All API keys belonging to the same account consume one shared per-minute allowance. Daily and monthly free quotas count the number of unique addresses submitted for validation, including addresses inside bulk requests.

Limits by tier

Tier	Request rate	Validation quota
Anonymous	30/min per IP	1,000/day per IP
Free (account)	60/min per account	10,000/day, 30,000/month
Starter	120/min per account	No monthly cap
Pro	500/min per account	No monthly cap

Brand-new free accounts ramp up: for the first 24 hours they are capped at 10 requests/min and 1,000 validations/day before settling at the full free limits.

A single-email or single-domain check consumes one validation unit. A bulk request consumes one validation unit per unique submitted address; duplicate entries in the same batch are counted once. Viewing an existing bulk result does not consume validation quota.

See Authentication for how tiers map to features and bulk limits.

Response headers

Responses normally carry these headers. Early failures and requests covered by overflow credits may omit them.

Header	Meaning
X-RateLimit-Limit	Your per-minute limit
X-RateLimit-Remaining	Requests remaining in the current window

When you exceed the limit

• Exceeding the limit returns 429 Too Many Requests.
• Sustained abusive traffic may result in an automatic IP ban.
• For per-minute limits, wait for Retry-After / retry_after. For daily or monthly quota exhaustion, use reset_at; repeated retries will not restore quota. See Error Handling.
• If your account holds credits, a burst over the limit spends a credit instead of failing (flagged by the X-Credit-Used response header).

Best practices

• Batch large lists. Bulk validation reduces HTTP requests, but still consumes one validation unit per unique entry.
• Cache carefully. Set an expiry and keep domain and individual email results separate. See Best Practices.