With the U.S. retail holidays Black Friday and Cyber Monday occurring in late November, Twilio anticipates a significant spike in short code SMS and MMS messaging. Due to the finite capacity of the U.S. messaging ecosystem, we’ve implemented a Heightened Awareness Period (HAP), effective November 23 - December 1, 2020.

During this period, you will have temporary account-level rate limits for short code SMS and MMS toward the U.S., determined by a formula described below.

This policy helps ensure that all customers have access to a reliable network that is optimally utilizing available capacity. 

Short Code SMS Rate Limits for November 23 - December 1:

• Accounts with 1 short code will have an account-level short code SMS rate limit that equals your current short code MPS. In other words, you will not see any change unless you add additional U.S. short codes during the HAP.
  
• Accounts with 2+ short codes will have an account-level rate limit that is equal to the highest value between:
1. Your peak sustained (60-seconds) SMS MPS within the past 12-months.
2. Calculated account-level rate limit based on the total MPS of your existing short codes.
3. Calculated account-level rate limit + additional throughput (MPS) that has already been purchased on short codes.  
• For customers with multiple short codes, your short codes will automatically share your account-level rate limit.  This means you could get higher peak throughput than typical on a single short code, depending on your message sending patterns. For example, if you have 10 short codes, you will be able to utilize up to 400 MPS on a single short code without any additional costs.
• Any additional MPS above the account-level rate limit can be purchased at a rate of $7 per MPS. If you are already paying for additional MPS on short codes currently, that will be applied to your account-level rate limit. 

Short Code MMS Rate Limits for November 23 - December 1:

• Twilio Accounts with 1 MMS-enabled U.S. short code will have an account-level short code MMS rate limit of 50 MPS.
• Twilio Accounts with 2+ MMS-enabled U.S. short codes will have an account-level rate limit that is equal to the highest value between:
1. Peak sustained (60-seconds) MMS MPS within the past 12-months, up to 150 MPS.
2. Calculated account-level MMS rate limit based on number of short codes, up to 150 MPS.
• For Twilio customers with multiple MMS-enabled U.S. short codes, your short codes will automatically share your account-level rate limit.
  

Frequently Asked Questions

Does this apply to entire messages, or message segments?

Unlike Twilio’s per-number rate limits, this account-wide short code MPS limit is based on entire SMS messages, and not the standard measurement of message segments. In other words, these account-wide short code SMS limits toward the U.S. will not change even if you send longer messages.

Please note, there is no concept of "segments" for MMS messages, only for SMS.

If I have subaccounts, do limits apply at the subaccount level?

Limits are applied on the parent account level, and include any subaccounts. Subaccounts do not provide any additional throughput.

What happens if I exceed the limit?

If you attempt to send more short code SMS or MMS messages than can be sent out per second based on your sending rate limit, the additional messages will be queued in the Twilio platform, and dequeued at your sending rate. The default maximum queue time is 4 hours. You can specify a shorter queue limit for your messages by setting a different Validity Period value on your Messaging Service or in your API requests.

If you queue up so many messages that you exceed your maximum queue length of 4 hours, the API will start rejecting new requests. If you are not using a Messaging Service, you will observe API errors with HTTP code 429 and error 20429. If you are using a Messaging Service, your message requests will be accepted by the API, but will subsequently fail with Error 30001 - Queue overflow.

For more details on Twilio’s standard sending rate limits and queue behavior, see Understanding Twilio Rate Limits and Message Queues.