Tropo FAQ

What can I build with Tropo?

With Tropo you can build nearly any voice application you can imagine, including speech-driven IVR, VoIP solutions and voice mashups. Subsequent releases will add support for web, IM, and SMS dialog interactions. Check out our documentation and sample apps at:

How much does it cost to use Tropo?

Right now, Tropo is in a free trial period. When we launch production usage, Tropo will have no contracts, no set-up fees and a low run-time cost. Premium features such as speech recognition, speech synthesis and call recording are included. Once the free trial period is over, Tropo developers will be able to purchase $50 usage blocks via PayPal or credit card. More information may be found on the pricing page here:

How long will the free trial last?

The Tropo free trial period will last for an unspecified time. We'll keep community members updated on our plans and timeframes. Please follow us on Twitter, FriendFeed or Facebook to be alerted to our plans.

How do I register for Tropo?

It’s so easy. Go to and click on the "Join Now" button. In less than a minute, you’ll have access to everything you need to create applications, including free file hosting and phone numbers.

Are there sample apps I can look at to help me build my application?

Yes, if you go to you will see sample applications and information for all the supported languages. The applications can be downloaded from that site or from our Github page at

If I do not want to host my scripts myself, how may I upload them to Tropo?

There are three options for uploading your scripts to Tropo for hosting:

What is the best way to create audio files for use with Tropo?

The Tropo platform supports a number of different audio formats. When converting your sound files for optimum performance in your application, it is always best to have your files in 8bit, 8Khz u-law format from the start. For more, please refer to this blogpost.

After I create a new account, I can not place outbound calls from my application. How may I enable this?

By default all new accounts have outbound dialing rights disabled. Simply make a request to 'moc.oexov|troppus#moc.oexov|troppus' and we will enable your application for outbound dialing.

Why did you choose to support Ruby, Groovy, PHP, JavaScript and Python?

We had to start somwhere and when we took at look at the language landscape for web developers, these five just seemed to us to be a great starting point.

What additional languages will be available?

After Tropo has been launched with the initial languages, we plan on adding more. If you have a language you would like to see supported, please let us know on the Tropo forum here:

What is Tropo built on?

Tropo is built on Java standards including SIP Servlets/JSR 289 and Java Scripting/JSR 223. This allows us to deploy the Java implementation of each scripting language that we make available. The list of the implementations are:

Language Implementation Version
Javascript Rhino 1.7_R1
Groovy Groovy 1.6.0
PHP Quercus 3.2.1
Python Jython 2.2.1
Ruby JRuby 1.1.6

What libraries can I use with Tropo?

For the supported languages, you can use most all of the "standard" libraries provided with that language's Java implementation as well as the Java API available in the JDK. We've restricted a few of them that may have security implications for our platform, but for the most part the full range of language libraries are available. You can see some of those libraries in use in the sample applications available at or

We will continue to evaluate the inclusion of additional custom libraries in each scripting languages, such as additional Python Eggs or Ruby Gems. Until then, the Java API is also available.

May I call the underlying Java API from my script?

Yes, it is possible to access the Java API available in JDK 6. The standard Java API is available on Tropo. For more information on accessing the Java API from your scripting language please refer to:

Scripting Language Howto
Javascript Scripting Java
Groovy TBD
PHP Working with Java classes in PHP
Python Interaction with Java Packages
Ruby Scripting Java from JRuby

Why may I not access Curl from my script?

Curl is a C library available on many operating systems. Many of the C implementations of scripting languages such as PHP make a Curl library available. Tropo uses the Java implementation of each scripting language, therefore any libraries only available in C are not supported by the respective Java implementation of that language on Tropo.

We recommend that when a certain library is not available, that the Java API be used from the scripting language.

How can I get involved with the Tropo developer community?

We are experimenting with several different means of connecting developers. Right now you can join us on IRC in the "#tropo" room on Alternatively if you use Skype you can join our Tropo Skype public chat by clicking this link. Watch our Tropo blog at to stay up on how you can connect to the Tropo community.

What is Voxeo’s involvement in Tropo?

Tropo is a new service offered by Voxeo and runs on Voxeo's rock-solid, fault-tolerant network infrastructure.

Does Voxeo still support XML-based programming?

Absolutely. Voxeo continues to provide the world's best and most standards-compliant VoiceXML and CCXML platform - and we will continue to support and invest in that platform. We are very involved in the efforts around VoiceXML 3 and continue to chair the CCXML activities within the W3C. XML-based telephony isn't going away - in fact it is getting stronger within the enterprise world. We look forward to continuing to help customers develop and deploy XML-based applications for may years to come.

Tropo opens up voice application development to more types of developers, including web developers who don't want to learn VoiceXML or simply prefer other languages.