API Rate Limits
These are the current limits for accounts using the Project Blue API. They're sized for steady, ongoing messaging — most integrations sending status updates or digests to existing contacts stay well within them.
The limits
Limit | Cap | What happens when you hit it |
|---|---|---|
API requests | 60 requests / minute, per API key | Returns |
Sends per line | ~15 messages / 10 minutes, per line | Queued, sent once under the limit |
New destinations per line | 50 new numbers / day, per line | Queued to the next day |
"New destination" means a number your line hasn't messaged before. Repeat destinations and any number that has texted you first (a reply) don't count against the daily new-destination cap.
Sizing your integration
If your automation is mostly status updates, reminders, or digests going back to contacts who've already messaged in, the per-line send cap and new-destination cap are unlikely to be a factor — those apply mainly to first-time outbound (cold outreach, reactivation campaigns).
If you're planning a larger cold-outbound push — for example, a reactivation campaign to hundreds of new contacts in a day — plan around the 50/day/line new-destination cap, and consider spreading it across multiple lines or multiple days rather than queuing it all at once, which also reduces the risk of carrier spam-flagging.
Good practices to avoid hitting limits
Batch your reads: use
/get-messages-apito pull messages rather than polling on every event.Space out first-time sends to new contacts rather than firing them all in a burst.
Watch for
429responses and back off/retry with a delay rather than immediately re-sending.