Limits

Item	Limit
Single SMS text	2,048 characters
Bulk send text	1,024 characters
Recipients per bulk send	1,000
Scheduling (send_at)	20 days
Messages per page (list)	20
Expiry of an unsent message	10 minutes by default
Send attempts	2 by default
Requests per API key	120 per minute (the test key is counted separately)
request_id memory	24 hours, per recipient

Rate

Every response shows your budget for the current minute: X-RateLimit-Limit, X-RateLimit-Remaining and X-RateLimit-Reset (reset time, in Unix seconds). Beyond it, the API answers 429 with code: rate_limited and a Retry-After header (seconds to wait). A bulk send counts as a single request: for many recipients, prefer it to one-by-one sends.

Questions about your integration: contact support from your dashboard.