Twilio imposes some rate restrictions on certain calls and text messages. Read on for full details.

Twilio Voice Calling

Outbound Calls

By default, each Twilio project can make 1 outgoing call per-second (CPS). This rate limit applies to both Outbound API-requested Programmable Voice calls, and Elastic SIP Trunking calls. API requests for calls that exceed the CPS rate limit will be queued, and executed as capacity is available. Exceeding the CPS rate on an Elastic SIP Trunk will result in a failed call.

Outgoing <Dial> calls for bridging and forwarding do not have a rate limit.

If your project requires additional outbound call throughput, please reach out to your Account Manager, or contact Sales.

Inbound Calls

Twilio places no limitation on the rate at which projects can receive inbound calls. Twilio will make an HTTP request to the request URL for each call received at your Twilio number. Therefore, please make sure your server is capable of handling the load if you are expecting a large amount of concurrent inbound traffic.

Twilio Text Messaging

Outbound Messages

The default processing rate for Outbound API-requested SMS messages on Twilio projects vary by phone number type and destination:

API requests for messages that exceed the above rates will be queued, and executed as capacity is available. If you will be sending more messages, you can purchase additional numbers to increase your capacity. For short code customers needing additional throughput, please reach out to your Account Manager, or contact Sales.

Please note that while Twilio releases messages to our carrier partners at these rates, your messages may be subject to mobile carrier filtering and can get blocked by the carrier(s) - read the article Can my Twilio SMS messages be blacklisted as spam? to learn more.

Inbound Messages

Twilio places no limitation on the rate at which a number can receive SMS messages. Twilio will make an HTTP request to the request URL for each message received at your Twilio number. Therefore, please make sure your server is capable of handling the load if you are expecting a large amount of concurrent inbound traffic.

Multi-segment and Concatenated Messages

If you have a message with multiple segments (a message over 160 characters will be broken up into 160-character segments), Twilio will queue the messages and release them at the rate of one message segment per second.

For example, if your SMS message to a US mobile number is under 160 characters and does not include any non-GSM characters, it only has one message segment, and will be released at the rate of one message per second. If your SMS message has three segments, it’ll take three seconds to delivery that single message.

Loop protection

To protect your project, messages cannot be sent more than 15 times in a 30 second window between your Twilio phone number and another number. Doing so may trigger a 14107 warningthat your message rate has been exceeded.

Calls Per Second (CPS) and Short Code throughput increases

Outbound Call and Short Code SMS throughput increases are available for a monthly fee. For pricing inquiries, please reach out to your Account Manager, or contact Sales.