Twilio imposes some rate restrictions for Programmable Fax. Read on for full details.
Notice: Twilio Programmable Fax will be disabled for all users on December 17, 2021. New and inactive accounts will lose access as of December 17, 2020. For full details, including migration options, see Fax Support on Twilio.
Notice: Receiving incoming faxes is generally available for Japanese phone numbers only. Inbound faxes to non-Japanese phone numbers are still considered beta, with no current plans for general availability. Support requests for beta and pre-release products are generally handled by our engineering team, and as such, response times are not guaranteed. For more information on Support limitations for beta and pre-release products, please see Twilio Beta Product Support.
Twilio places no limitation on the rate at which projects can receive incoming faxes. Twilio will make an HTTP request to the url or service configured for the phone number each time a fax is received. Therefore, if you are expecting a large amount of concurrent inbound traffic, please make sure your server is capable of handling the load.
For help readying your Twilio number for incoming faxes, please see our article Configuring Phone Numbers to Receive Faxes.
Each Twilio number can request 1 originating outgoing fax per-second. Each page faxed will take 30-60 seconds to process on average. Sending a second fax to the same number, while your original fax's pages are still in transmission, will lead to a failed fax with the status "busy".