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. The code you write also works over text messaging. Check out our documentation and sample apps at:

Does Tropo replace my mobile or landline phone service?

No, Tropo is used to automate communications. Tropo doesn't provide "dial tone", SIM cards, or SIP trunking, but instead gives you a simple way to write code that can make and receive phone calls or text messages. Tropo isn't a substitute for basic phone service, and can't be used for emergency calls.

How much does it cost to use Tropo?

Tropo is 100% free for development usage. Once you're ready to move your application to production, you pay only for what your application uses: a low per-minute rate for voice and a per message rate for text messages. There are no contracts, no set-up fees, and no minimums. Premium features such as speech recognition, speech synthesis and call recording are included at no extra cost. Detailed pricing can be found on our pricing page.

How long will the free trial last?

Tropo is always free for development use, it's not a limited time offer. Keep your application in development as long as you need to, without having to worry about time limits or eating up usage credits.

How do I register for Tropo?

It’s extremely easy. Just hit our registration page, give us your email address and pick a username and password. In less than a minute, you’ll have access to everything you need to create applications, including free file hosting and phone numbers. Then follow our quickstart guides to have your first application up and running in less than 5 minutes.

What countries are numbers available in?

We offer toll free and local numbers in the US, and local numbers in 40 other countries: Australia, Austria, Belgium, Brazil, Bulgaria, Canada, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hong Kong, Hungary, Ireland, Israel, Italy, Japan, Latvia, Lithuania, Luxembourg, Malta, Mexico, Netherlands, New Zealand, Norway, Panama, Peru, Poland, Portugal, Slovakia, Slovenia, South Africa, Spain, Sweden, Switzerland, UK, US (including Puerto Rico).

Some countries have laws restricting who can own numbers. Read the details on these restrictions.

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. Additional sample application can be found on our Github page at

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

There are two 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.

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

We had to start somewhere - when we took a look at the language landscape for web developers, these five seemed to be a great starting point. Want to use a different language? Our WebAPI can be used with any language you can run on your server.

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:

  • Javascript - Rhino - 1.7_R2 / ECMA-262 Edition 3
  • Groovy - Groovy - 1.8.5
  • PHP Quercus - 4.0.36 (equivalent to PHP 5.4)
  • Python - Jython - 2.7 (equivalent to Python 2.7)
  • Ruby - JRuby - 1.7.21 (equivalent to Ruby 1.9.3)

What libraries can I use with Tropo?

With Tropo WebAPI, you host your own code, so you can use any libraries available on your server. With Tropo Scripting API, 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.

Can 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:

Why can't I use curl in Tropo Scripting?

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. Some languages, like PHP, have implemented curl in Java. For these languages, all of the curl features are available.

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?

Join our forums, hop into the #tropo IRC channel, or follow us on Twitter as @tropo. And as always, watch the Tropo blog to stay up on how you can connect to the Tropo community.