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+01 (414) 230 - 5550
Experienced developers
ready to join your team or
execute your new project


Years of experience


Software Projects
Design and build an end-to-end web and mobile application with a fully-fledged team.
Staff Augmentation
Augment your in-house team with developers for expertise, capacity and speed.
Mentoring & Workshops
Boost your developers’ skills with mentoring & workshops delivered by our experts.
Clients trust us
For over 12 years we have successfully facilitated software outsourcing for clients in Europe and United States, delivering ambitious and compelling web and mobile applications throughout a wide variety of business domains and industries.

Selleo have allowed us to quickly scale our existing teams with additional developers, often within a couple of weeks. They're a pleasure to work with and have always delivered outstanding quality!

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Jan Thomas

Director of Product, Game Genetics, Germany

The team at Selleo have been fantastic to work with. They are highly skilled and knowledgeable programmers and designers who are very conscientious of delivering the best product possible. I would definitely recommend Selleo to anyone looking to build an excellent product and enjoy the process as well.

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Jamie Engel

Founder and CEO of Neutopia, AU

I look for 5 key things in a software development partner: great programmers, consistent quality, excellent value, a responsive management team, and a fun experience. Selleo is a solid 5 out of 5 by my standards.

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Myron Weber

CEO, Northwood Advisors, The USA

Unleash your full business potential
with custom tailored software

For over ten years we have successfully facilitated software outsourcing for several clients in Europe, Australia, and the U.S., delivering ambitious and compelling web and mobile applications throughout a wide variety of business domains and industries.


Cutting-edge applications
require cutting-edge skills

Whenever you want to handle a new project, deliver essential features or need a staff with specialized skills or industry expertise, our web and mobile developers help you to increase overall productivity. As they are working in responsive business units with a high level of soft-skills team-wide, you can communicate with them and manage your project as if they were sitting in the same office.

Extend your in-house team

Increase your velocity and impact software development speed together with the code quality. We have delivered outsourcing and team augmentation services to companies from e.g., New York, Sydney, Berlin, Hamburg, Munich, Geneva, Copenhagen, and Oslo.

Add new skills and expertise

Building a cutting-edge technology company is time-consuming. With us, you can establish digital savvy teams, benefit from knowledge transfer and adopt modern technology stacks to impact the long-term viability of your business.

Embrace tech stack complexity

Our developers have not only the current capabilities you need but also an ability to build new ones rapidly. With the vast diversity of skills required and partnership with other specialized companies, we can deliver even the most technologically challenging software solutions.

Back-End Development

Almost every web application needs a back-end part to handle connection with the database, periodic tasks or verification of users and data. We have multiple back-end developers skilled in different technologies who will be able to transform your business ideas into a working application.

Ruby on Rails Development

If the speed of development is important for you, Ruby on Rails as your back-end technology is a perfect choice. It's known for the ease of integration with a huge array of ready-to-use application parts, which our back-end developers can easily leverage, creating a business solution for you.

NodeJS Development

Node.js revolutionized the JavaScript world, as it allowed code execution outside of the browser. On top of this technology, many tools were born and our developers use Node to build the production code, run back-end servers, as well as manage open source dependencies during web application development process.

Phoenix Development

High speed of operation, low resource load and productivity during development are the reasons why Phoenix stands out from other back-end technologies. On the top of that, the system created by our developers will be able to gracefully handle occurring errors, reliably serving your customers needs.
Front-End Development

Nowadays, more and more businesses increase the share of the front-end part in their application stacks. Our JavaScript engineers during the process of front-end development will help you provide a great user experience to the ones using your application. Our developers are knowledgeable of using React, Angular and Ember technologies.

ReactJS Development

Our developers praise React.js for its simplicity and composability. It can be easily integrated with a variety of other technologies which provide solutions to business problems, as well as improve productivity during the development of your application.

EmberJS Development

Having or planning big front-end application, but you want to leverage on already solved technical problems, so our developers can focus on building the actual solutions you need? Ember.js is the technology to go. It comes with a bunch of tools setup and ready to use immediately.


Angular is a framework that makes it easy to build applications with the web. Angular combines declarative templates, dependency injection, end to end tooling, and integrated best practices to solve development challenges.
Mobile Development

Targeting your service to the Android and iOS users and wanting to reach them both with one application? Achieve your goals by having our web developers create Mobile Web App for you. That way any smartphone user with an Internet browser will be able to use your app.

React Native

Do you want to provide your smartphone target users with a truly native experience? With React Native development of mobile apps, it is easier than ever before. This technology allows our developers to craft solution targeting iOS and Android systems at the same time, saving lots of your time.


Here at Selleo, our developers make sure the various programming languages they are using allow them to achieve the highest level of productivity and speed, while maitanining readability and introducting revolutionary features of our products.


Ruby, as one of the high-level, battery-included languages, allows our developers to be more productive. It is known for its clean, English-like syntax, object-oriented paradigm and a helpful community. That's a perfect choice if you want to leverage your application at community-developed solutions.


Elixir running on Erlang VM provides high speed of execution, while not sacrificing readability and maintainability of the whole system. Our developers can use Elixir on the server side of your web application and extend the language wherever it is useful. Thanks to this brilliant technology, they can focus on crafting the optimal solution for your business requirements.


Everyday JavaScript is getting bigger. Growing community and number of tools ready to be used by our front-end developers makes using this web development technology the safest bet for the future. On the top of that, JavaScript can be used both in the front- and back-end of the application stack.


In web development, it is important to be up to date and use the most effective tools for a certain job. ES2015 is one of such technologies. This milestone in the JavaScript world is a must-have in every front-end engineer toolbelt and our developers keep up with the pace.


The ES2016 release of JavaScript standard adds a few new features useful during web application development. While being relatively small, it is another step that makes JavaScript more like a modern technology and our developers incorporated ES2016 in their daily work.


Our developers prefer using ES2017 in front-end applications because it brings game-changing features to the JavaScript language. One of the revolutionary changes are Async functions which resolve problems with managing the asynchronous pieces of code. Together with other improvements ES2017 substantially simplifies and speeds up web application development.
APIs, 3rd Party Integrations

API is like a waiter in a restaurant delivering orders and food. It interacts between applications data and devices creating connectivity. 3rd party integration is super important in single web development projects since we strive to deliver to our customers the best user experience possible.

Json API

JSON API is a specification for how a client should request that resources be fetched or modified, and how a server should respond to those requests. It is designed to minimize both the number of requests and the amount of data transmitted between clients and servers.


GraphQL is a query language specification designed to build client applications by providing an intuitive and flexible syntax and system for describing their data requirements and interactions. It gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time.

Payment solutions

Paypal, Skrill, QuickPay, Braintree, Stripe

E-mail and text delivery

Sendgrid, Postmark, Mailgun, MailChimp, Mandrill, Cloudmailin, AWS SES

Sending and managing documents

Rightsignature, Sharepoint, eBridge

Data storage

AWS S3, Dropbox, Firebase, Azure DB
Technology Stack

With the wide spectrum of technologies we strive to ensure support for a variety of popular web and mobile platforms. The list below contains a representative sample of technologies and tools we have worked with to date.

Back-end QA

RSpec, Capybara, Cucumber, Brakeman, Rubocop, RubyCritic, ExUnit

Application Servers

Puma, Thin, Passenger, Unicorn, nginx


PostgreSQL, Elastic Search, Neo4j, MySQL, MongoDB, Microsoft SQL Server, Firebase, Redis

Servers & Datastorage

Heroku, Amazon Web Services (EC2, OpsWorks, ELB, S3), Docker, Memcached

Front-end QA

Jest, Enzyme, Sinon, Mocha, Chai, QUnit, Jasmine, Chrome, Firefox

Presentation tire

HTML5/HAML/SLIM, CSS3/SASS, Bootstrap, Material Design