Twilio error 63018 fires when your WhatsApp message sending rate exceeds the limits imposed by WhatsApp's Business API for your WhatsApp Business Account's current messaging tier. WhatsApp enforces per-phone-number rate limits on template message sends, measured in unique users contacted per day (not per message), and exceeding this daily limit causes all further template sends to fail with 63018 until the 24-hour window resets. The rate limit is directly tied to your account's messaging tier, which WhatsApp adjusts based on your account's quality rating and sending history.
What Causes This Error
WhatsApp divides businesses into messaging tiers that define the maximum number of unique users you can send template messages to in a rolling 24-hour period: Tier 1 allows 1,000 unique users, Tier 2 allows 10,000, Tier 3 allows 100,000, and Tier 4 (unlimited) requires a proven track record of high-quality messaging. Exceeding your account's current tier limit causes 63018 for every additional template send attempt until the rolling 24-hour window resets. A sudden high-volume campaign or broadcast that sends the same template to a large list within a single 24-hour period is the most frequent operational cause, particularly for accounts that have been recently set up and are still at Tier 1 with a 1,000-user daily limit. Twilio's own API rate limits for the WhatsApp channel also apply at a lower level: sending more than 80 template messages per second or more than 4,800 per minute to the Twilio API itself can cause rate rejection at the Twilio layer before reaching WhatsApp's infrastructure. A recent downgrade from a higher messaging tier due to a poor quality rating (caused by high opt-out rates or spam reports) reduces your daily unique user limit immediately, and a campaign volume that was within the old tier limit will suddenly exceed the new lower limit.
How to Fix It Step by Step
Check your current WhatsApp Business Account messaging tier and daily usage in the Meta Business Manager under WhatsApp Manager, then Overview, or in the Twilio Console under the WhatsApp sender detail page, to understand how many unique users you have messaged in the current 24-hour window and what your tier limit is. If you have hit the tier limit, pause the current send campaign and reschedule the remaining messages to be sent after the 24-hour window resets, spreading subsequent campaigns across multiple days to stay within tier limits. Implement exponential backoff with jitter in your message sending queue: when a 63018 error is received, pause the queue for a calculated delay (starting at 60 seconds and doubling up to a maximum of 3600 seconds), then retry a single message to confirm the window has reset before resuming full send rate. If your business legitimately needs to send to more than 1,000 unique users per day and you are currently at Tier 1, the pathway to tier upgrade is to maintain a high quality rating (above Medium) for 7 consecutive days while sending close to but not exceeding your current tier limit, which triggers an automatic upgrade to the next tier.
How to Prevent It from Recurring
Implement a rate limiter in your message sending service that tracks the number of unique recipient phone numbers messaged in the current rolling 24-hour window and stops accepting new sends when the count approaches 90 percent of your current tier limit, queuing the overflow to the next day rather than attempting sends that will fail with 63018. Spread large broadcast campaigns over multiple days by dividing recipient lists into daily batches sized at 80 percent of your tier limit, building in a safety buffer that prevents hitting the limit even if the sending pace varies slightly. Monitor your WhatsApp quality rating in the Meta Business Manager regularly and treat a decline in quality rating as an urgent signal to review your content and targeting, since a tier downgrade (which happens automatically when quality drops below a threshold for 7 days) will immediately make your current send volumes exceed the new lower limit. Request a tier upgrade proactively by using the WhatsApp Business API throughput upgrade request process if your business has grown to consistently require more than your current tier allows, rather than waiting to hit the limit.
When to Call a Specialist
If your business requires sending template messages to more than 100,000 unique users per day and needs to reach WhatsApp's unlimited Tier 4, a specialist can design the multi-month quality maintenance strategy required to achieve this tier, as Meta reviews accounts manually for Tier 4 eligibility and requires demonstrated high-quality sending history. A specialist is also valuable if your account has been downgraded due to a quality issue and you need to both restore the quality rating and manage current send volumes within the reduced tier limits simultaneously, as these two objectives can conflict and require careful balancing. You should escalate if 63018 errors are occurring at volumes well below your current tier limit, as this can indicate an account-level restriction applied by Meta that is separate from the standard tier system and requires investigation through Twilio support.
Conclusion
Error 63018 is a WhatsApp messaging tier rate limit that is resolved by implementing a daily unique-user counter, spreading campaigns across multiple days, and working toward tier upgrades through sustained high-quality sending. If this error is blocking your production system, contact our team and we will diagnose and fix it within the hour.
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