Hacktoberfest Hack Day Budapest x Green Reliable Software Budapest Submission deadline.

Hacktoberfest 2026

Thursday October 29, 2026

11:59AM to Oct 30, 11:59PM UTC+02

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Király u. 26
Budapest, Pest 1061
Hungary

Event Description

HACK4EARTH 2.0 returns this October as a month-long Green + Open Software initiative.

Under the theme Greener Fields, builders will explore how open technology can make the systems we depend on more secure, efficient and resilient.

Participants will be free to define their own problem, stack and approach across three broad technical directions:

SECURE: cybersecurity, privacy, cryptography, software supply chains and trustworthy systems
EFFICIENT: green software, computing efficiency, cloud, data, AI and hardware
RESILIENT: food, water, energy, communications, climate and critical infrastructure

The hackathon itself is free to participate in and will run throughout October 2026, with online building, technical sessions, open-source activities and selected physical activities in Budapest.

Visit our main Hackathon page for detailed challenge outcomes.

Who can attend?

Locations have different requirements for who can attend. This location is open to the following:

Schedule

1 October · Opening Day

HACK4EARTH 2.0 begins

Participant onboarding
Challenge and track introduction
Open-source contribution guidance
Team formation and project scoping
Hacktoberfest Hack Day Budapest activities
Month-long building officially opens

Projects may work across one or more technical directions:

SECURE

Cybersecurity, privacy, cryptography, software supply chains and trustworthy systems.

EFFICIENT

Green software, computing efficiency, cloud, data, AI and hardware.

RESILIENT

Food, water, energy, communications, climate and critical infrastructure.

Week 1 · 1–7 October

Who Builds the Commons?

We begin with the foundations of open technology.

Topics include:

Open-source communities and maintainership
Digital commons
Security and software supply chains
Trust, dependency management and responsible contribution
The people and infrastructure behind open software

SECURE track sessions begin

Small Challenge:

Break My Dependency Chain

Week 2 · 8–14 October

Who Pays for the Commons?

Open source may be free to use, but it is not free to build, maintain or operate.

We explore:

Sustainable open-source business models
Maintainer economics
Infrastructure and hosting costs
Commercial open source
Developer experience
Funding public digital infrastructure

Track speaker sessions and project workshops continue.

Week 3 · 15–21 October

Can You Measure What You Built?

This week moves from intention to evidence.

Topics include:

Software carbon measurement
Energy and compute efficiency
Green software metrics
Cloud and infrastructure efficiency
AI and hardware impact
Measuring real-world outcomes

EFFICIENT track sessions

Small Challenge:

30-Minute Carbon Hunt

Teams begin preparing evidence, measurements and documentation for their final submission.

Final Build Week · 22–28 October

Does It Survive Pressure?

Projects are tested against real-world constraints.

We explore:

Reliability and failure
Critical infrastructure
Climate and environmental pressures
Food, water and energy systems
Communications resilience
Security under stress

RESILIENT track sessions

Small Challenge:

Design for Failure

Teams refine, test and document their projects.

29–31 October

Final Sprint + Bingo

The final build window opens.

Final project development
Open-source contributions
Documentation and impact evidence
Community demos
Bingo challenge
Submission preparation

31 October · 23:59

HACK4EARTH 2.0 submissions close

All code, documentation and required project materials must be submitted before the deadline.

The continuation prize: TraceLab

Up to 8 selected teams may be invited to continue developing their work through TraceLab, a three-month venture and validation programme connecting promising solutions with mentors, technical support, ecosystem partners and potential funding opportunities.