Clojure is designed to simplify software development.

Clojure is a functional programming language that features elegant concurrency support, a rich set of immutable, persistent data structures, and frictionless Java integration.

Developers are increasingly being asked to build larger and more capable systems, with more features, and handling more information. Building solutions with complex tools on top of complex infrastructure is a path to more complexity in your life, and often a recipe for failure. And yet there are very few truly simple tools and systems with which to build your solutions.

Clojure’s approach to programming enables you to write most of your applications’ code as series of pure functions, each one operating only on the immutable values passed in. Since pure functions have no side-effects they are easy to understand, easy to test, and are inherently thread-safe. On top of that, Clojure provides a rich set of features that allow threads to coordinate state changes in a consistent, controlled fashion.

Clojure's Lisp based syntax is incredibly easy to learn: Most programmers can pick up the basics in an afternoon. It is also very concise, which means you spend less time typing and more time designing.

We built Clojure.

At Cognitect, we have a commitment to the Open Source Community, and a special love for Clojure in particular. Cognitect's Rich Hickey built the language to bring simplicity to the most complex software problems, and we are dedicated to a future where Clojure's strength enables organizations everywhere to build simple, maintainable software that stands the test of time.

Success Stories

  • Walmart used Clojure to create a robust data management system that supports over 5,000 stores and integrates online and mobile data.


    Learn how Walmart is running Clojure at Scale.

    "Our Clojure system just handled its first Walmart black Friday and came out without a scratch." - via Twitter, 11/28/2014

    Anthony Marcar Senior Architect
  • Chartbeat uses Kafka and Clojure to build a contextual site overlay which tracks internal traffic at a rate of over one million clicks per minute in real time.


    Watch Devon discuss how they use Clojure to process a stream of activity of tens of millions of users.

    When we needed to extract insights from hundreds of thousands of requests per second in realtime, we knew Clojure was the answer. Clojure is really awesome for general stream processing.

    Devon Peticolas, Sr. Backend Engineer and Team Lead
  • 8th Light worked with a new-to-Clojure client team to complete their first Clojure project in just a month, from design to deployment.


    Read about why they consider Clojure a boring technology, and why that's a good thing.

    Clojure's flexibility, interactive development, and tooling have helped us to iterate and continuously deliver a product our clients can be proud of.

    Colin Jones CTO
  • Consumer Reports chose Clojure and Datomic to bring together all their underlying backend systems and databases. Their new enterprise-wide container service enables developers to create applications providing the data consumers are searching for quickly with decreased risk and effort.


    Watch Paul deGrandis discuss Unlocking Data-driven Systems.

  • Cicayda used Clojure, Datomic, and ClojureScript to build a robust, multi-tenant cloud hosted SaaS that allows clients to manage diverse data and load profiles.


    Learn how they used the familiar principles of Clojure to build this legal data service.

    ClojureScript has provided us with a unified development environment on both sides of the wire and has helped us push toward a data-oriented UI.

    Jonathan Boston Software Developer
  • Puppet use Clojure to build Trapperkeeper (and more), relying on Clojure's simplicity to build an agile, scalable platform.


    Read about Trapperkeeper. Or Dig deeper. Or read about PuppetDB.

    Clojure is a functional programming language from top to bottom. This means that code written in Clojure is very modular, composable, reusable and easy to reason about.

    Chris Price Software Engineer
  • Beanstalk switches to Clojure to speed up caching by 20x.


    Read about the love.

    Yesterday we deployed to production a rewrite of Beanstalk’s caching system written in Clojure. It is 20 times faster than the previous version ... and allowed us to bring the latency between committing a change to a repo and seeing the update in Beanstalk’s UI to an average of 20 ms.

    Dima Sabanin
  • MailOnline.com rebuilds publishing platform in Clojure.


    Read about Clojure at a newspaper.

    Yet fundamentally we hadn’t written much code. I raised this sheepishly with the CTO and his response was: “that’s how I know it’s the right solution”. Clojure is the winner here.

    Jon Pither Co-founder, Juxt.pro
  • DRW Trading Group has adopted Clojure with great success.


    Watch Jay discuss why DRW chose Clojure.

    Clojure wasn’t the first language that I’ve introduced to an organization; however, it’s unquestionably the most successful adoption I’ve ever been a part of. The use of Clojure has had many impacts on the firm: culturally, politically, and technically.

    Jay Fields Software Engineer
  • IOOF worked with Thoughtworks to quickly replace and improve a critical component of their financial services platform.


    Read about recreating their superannuation services.

    The project was a discrete module and allowed us to build it as a service which fits with our architecture goals. Importantly it required integration with our core administration system and that posed no challenge. Clojure allowed us to quickly and easily implement all the changes required to bring this custody function back in-house.

    Andrew Todd CIO
  • Thoughtworks leverages Clojure to accelerate a Java team.


    Read about using Clojure to deliver early and under budget.

    We discussed the existing Clojure community, the maturity of the language itself and the momentum we saw in the industry. Companies are seeing speed to market deliveries, that are based on Clojure.

    Dave Eilman
  • The Climate Corporation uses Clojure to help the world’s farmers sustainably protect and care for their crops.


    Read about how they used Clojure to build a versioned weather datastore.

    All our models, datastores, and services are built in Clojure. We find that Clojure’s support for parallelism makes it easy to run complex models with low latency.

    Leon Barrett Software Engineer
  • Precursor is real-time collaborative prototyping for teams built with Clojure, ClojureScript, and Datomic.


    Read about how Precursor uses ClojureScript to make designers productive.

    Learning to use ClojureScript, Om, and React finally made me feel like I was taking ownership of my design work from beginning to end.

    Danny King Co-Founder/Designer
  • Sonian has been using Clojure in production at a large scale to develop a common foundation for back-end services.


    Read about how Sonian stays SAFE.

    Clojure gives us a performance boost at both ends of the software development lifecycle: we can build new features as quick as any Python or Ruby shop, and when we ship it to production it runs as fast as any Java application.

    Ron Toland Clojure Engineer
  • Appsflyer develops in Clojure for scalability and for the business agility it enables. They can grow and adapt as fast as the mobile advertising market.


    For more about Appsflyer, visit their website. And check out their blog post about using Clojure in end-to-end production.

    When we transitioned from millions of daily events to billions, we knew that Clojure was the answer.

    Reshef Mann CTO
  • Atlassian is using Clojure to build realtime collaboration features into both new and existing products.


    Leonardo Borges explains why Atlassian chose Clojure and the exciting results the team has achieved in his recent presentation at EuroClojure 2015.

  • Base2 used Clojure to develop a feature-rich onboard diagnostic system for the Boeing 737 MAX. They structured the application with a service framework and message queues to enable communication between disparate parts of the service while preserving separation of concerns.


    Watch Donevan discuss the development of this onboard application in this Clojure/west 2016 presentation.

    We picked Clojure for this project due to its ability to run parallel processes well, the strength of the available libraries, and because Clojure, which is a Boeing approved language, uses the JVM.

    Donevan Dolby Software Engineer
  • Room Key works with Cognitect and leverages Clojure and Datomic to build a rapidly scalable, highly agile cloud-based hotel search engine.


    Read about 60,000% growth using Clojure and AWS. Or a case study about our collaboration. Or about how they use Datomic.

    [We] knew Cognitect would provide the kind of support we needed. They have been our partner in every sense of the word. They resolved most of the few problems we encountered before I got to them.

    Colin Steele CTO
  • Greenius chose Clojure and Datomic to build a scalable, agile platform for gardeners to collaborate and share ideas.


    Learn about their ClojureScript integration roadmap.

    [We designed our software] with just immutable data structures and pure functions (with much less code than traditional OO languages) allowing us to focus on our core business requirements rather than inherent technological problems.

    Asier Galdos Co-founder/developer

Tools for Information

Our open source tools emphasize the power of data, making it easier to reason about and reveal information.

Built for the Cloud

The Clojure stack is ideally suited to use in the cloud - our focus on composability, immutability and data provides a better set of tools for building new types of systems in the cloud.

Simple Tools, Simple Systems

The Clojure stack has simplicity as a core principle, and yields systems that are easier to understand and maintain.

State of Clojure and ClojureScript

Learn more about our consulting, support and training offerings for Clojure and ClojureScript.

Learn more