Registering and using a developer account

InterFAX offers developers the opportunity to register and test its fax service for free. This will enable developers to develop their applications and test the integration of InterFAX throughout the development process.

A developer account:

  1. Is completely free of charge, and
  2. Has no limit on the length of time it is available to you

(for other common questions regarding developer accounts, please visit our developer FAQ).


When setting up an InterFAX developer account, InterFAX enforces some limitations on the account in order to allow a free service for testing. These limitations are:

  • By destination: a developer account can send faxes to one of the following numbers:
    • A designated fax number provided during registration (see below).
    • A dummy number that will mimic behavior of fax delivery (see below).
  • By total cost: a developer account is issued with a certain amount of free credits for sending faxes. The cost of faxes sent will be deducted from these credits until they run out. Once depleted, the developer will need to contact our developer support to add more credits to their account.

Registration process

In the registration form to set up a new developer account, there is an option to select whether a designated fax number should be provided. If a designated number is not provided, the developer account will still be able to send faxes to dummy numbers provided by InterFAX (see below). Additionally, you may contact our developer support to request adding a designated number to the account at any time after opening an account.

Sending faxes with your developer account

Sending faxes to dummy numbers – Test Simulator

InterFAX provides dummy numbers for testing purposes in order to demonstrate the transmission and handling of faxes within the system. While these faxes will not be sent out to a real fax number, the user experience in the InterFAX system will demonstrate how an actual fax will be processed and completed; both successfully and in failure.

To send a fax to a dummy number, simply submit the fax to a number format as +999-9999-[result code]. The [result code] should be replaced with the result code that you would like to simulate in InterFAX (the result code should be one of InterFAX’s fax transmission status codes).

Please note that the [result code] cannot be longer than 4 digits.

For example:

  • In order to experience a fax that results in success, submit the fax to number +999-9999-0.
  • In order to experience a fax that results in failure due to a busy signal, submit the fax to number +999-9999-6017

Sending faxes to designated fax number

The designated fax number is a number that you provide upon registration, and to which you can send faxes for free. This can be your office fax machine, for example.

When sending a fax to the designated number, you should format the fax number according to the InterFAX number format instructions (for example, +1 212 999 8888).

You can view your designated fax number online through our control panel under “My Settings” > “Developer Options”.

Sending faxes to other numbers

While using a developer account, you are limited to sending faxes to either the designated fax number or the InterFAX dummy numbers. If you submit a fax to a number that is not your designated fax number or one of the dummy numbers, the request to submit the fax will fail with status code -111 (see web service status codes).