Duke holding a magnifier

CheerpJ: The Hackathon

The Java in the browser challenge!

14 Nov - 1 Dec

📍Leeds & virtual

About this event

Join this challenge to create a WebApp solution that integrates CheerpJ in the context of scientific software!

The winner team gets a sweet 500 GBP gift card 🚀!



CheerpJ is a tool to run Java code in the browser without requiring a local Java installation. This allows for a wide range of applications to be available in the browser client-side, which might otherwise not be accessible without local installations and dependencies.

Read more in this blog post .

How to participate

Cats in a box

Step 1: Register & Join our Discord

Register your interest on this form and don't forget to join our Discord server ! We use our Discord server as the main communication platform for this event, where we will be streaming live, giving technical support, and posting announcements!

Participants can register and join a team at any time before the project submission deadline.

cat typing

Step 2: Secure your spot at the venue

This event offers a hybrid experience - you can fully engage online or, if you fancy, join us in-person for the opening and closing sessions. If you want to attend in person, please secure your free individual tickets. Pssss... There will be gifts and snacks!

To fit everyone's schedule we will be hosting two opening sessions on Friday, 14th November. You can choose to attend 10:00 am -13:00 pm or 14:00 pm - 17:00 pm UK time.

Ticket

Step 3: Team up and work on your project!

Now it’s time to put your hands on your project! You can work on your project as a solo participant or in a team of up to 5 members. Don't be afraid to find a team by engaging on our Discord server, meeting new people at the opening session, or by inviting your friends!

Our core CheerpJ developers will be helping via Discord text channel with any technical questions during this journey. Don’t miss out on the opportunity to learn from the experts!

Winner

Step 4: Submit, present, and await

Submit your creation by the deadline (Monday 1st of December at 11:00 am UK time). Instructions on how to submit coming up!

As a non-mandatory step, we encourage all teams to prepare a 5-minute presentation to share your creation with the community on the closing session! Presentations do not affect your final score, so don’t worry too much and just have fun ;)

The final results will be published on December 15th on our Discord server.

For more useful information and guidance, don't forget to read the docs or ask any technical questions on our Discord Server.

Support CheerpJ docs

Judging panel

Elisabeth Panholzer

Elisabeth Panholzer

Software Engineer

Leaning Technologies

Alessandro Pignotti

Alessandro Pignotti

Chief Technology Officer

Leaning Technologies

Ethan Hale

Ethan Hale

Software Engineer & creator of Logisim.app

DRS Software

Jeff Martin

Jeff Martin

Founding Engineer & lead on SnapCode

ReportMill Software

Rule book

Rules of the Game

The boring but highly important section. Please make sure to follow these rules for your project and participation to be valid.

The Important Stuff

  1. All projects must use CheerpJ actively. Projects where CheerpJ is imported but not used will be discarded.
  2. Submit your project no later than 1st December 2025, 10:00 AM (UK time).
  3. No further commits are allowed after the deadline. Fork your repository if you wish to continue working afterward.
  4. All project repositories must remain public and open source on GitHub.
  5. Projects must be deployed and hosted publicly (e.g., GitHub Pages).
  6. Credit third-party components and ensure licensing compliance.
  7. If using generative AI, provide proper credit.
  8. Teams must have between 1 and 5 registered members.
  9. Winning team: £500 gift card. The team leader will be contacted via Discord to arrange delivery.
  10. Projects promoting violence, hate, or discrimination will be disqualified. Respect and professionalism are expected at all times.
  11. Participants must be 18+. Minors may join only with full parental consent (contact stefano@leaningtech.com).
  12. All qualified projects will be showcased in our official hackathon repository.
Calendar

Agenda

Please consider this agenda is subject to change, stay tuned!

We understand that our hackathletes might have other responsibilities throughout the day; therefore, we are hosting two opening sessions with the same content. Choose the one that suits you best!

Friday 14/November/2025

Opening session 1 (10:00 - 13:00)

UK Time Event Description Leeds site Discord
10:00 Reception Ice breaker, gifts & welcome chat! Venue opens -
10:30 Welcome talk Event overivew, rules & submissions Main venue screen (Seminar room 1) Stream on Stage
11:00 Introduction to CheerpJ workshop Beginner session: Using CheerpJ Main venue screen (Seminar room 1) Stream on stage
12:00 Guest talk “Building logisim.app with CherpJ” by Ethan Hale Get inspired to build your own project. Main venue screen (Seminar room 1) Stream on stage
12:30 Closing remarks Q&A and key event reminders Refreshments provided Stream on stage

Opening session 2 (14:00 - 17:00)

UK Time Event Description Leeds site Discord
10:00 Reception Ice breaker, gifts & welcome chat! Venue opens -
10:30 Welcome talk Event overivew, rules & submissions Main venue screen (Seminar room 1) Stream on Stage
11:00 Introduction to CheerpJ workshop Beginner session: Using CheerpJ Main venue screen (Seminar room 1) Stream on stage
12:00 Guest talk “Building logisim.app with CherpJ” by Ethan Hale Get inspired to build your own project. Main venue screen (Seminar room 1) Stream on stage
12:30 Closing remarks Q&A and key event reminders Refreshments provided Stream on stage

Saturday 15/November/2025 - Sunday 30/November 2025

UK Time Event Description Leeds site Discord
11:00 Online technical support starts Get help from the experts! - #hackathletes-support channel

Monday 1/December/2025

Closing day (10:30 am - 17:00)

UK Time Event Description Leeds site Discord
10:00 Submissions Closed Make sure to submit your project before this time - -
10:30 Venue doors open Come to the venue, grab your seat, and chit-chat. Seminar 1 -
11:00 Presentations block 1 - Seminar 1 (Main Screen) Stream on stage
13:00 Lunch break and Networking (food is on us!) Seminar 1 -
15:00 Presentations block 2 - Seminar 1 (Main Screen) Stream on stage

Monday 15/December/2025: Winner Announcement!

We will announce the winning team as well as the scoring for all qualified projects. Team leaders will receive feedback via private message on Discord :) Stay tuned! 🏆