Input-Output Hong Kong (IOHK) is a blockchain research and engineering company best known for designing and building Cardano (ADA). It was founded in 2015 by Charles Hoskinson, a co-founder of Ethereum, and Jeremy Wood, and was originally registered in Hong Kong, which gave it its name. The company later rebranded as Input Output Global (IOG) and now generally presents itself as Input Output. It has staff in many countries and has published a large body of academic research on blockchain protocols.
IOHK is one of three organizations historically responsible for Cardano, alongside the Cardano Foundation, a Swiss non-profit focused on standards and adoption, and Emurgo, a commercial arm that invests in and builds on the ecosystem. IOHK developed most of Cardano's core software, including its node, wallet and smart-contract platforms, under contract. It has also worked on other projects, including a period as a development team for Ethereum Classic and the privacy-focused network Midnight.
IOHK in plain terms
If Cardano is a public road network, IOHK was the main engineering firm hired to design and build it. It drew up the plans, wrote much of the software that makes the network run and published detailed research explaining why the design should be safe. Other groups look after the road's rules, promote its use and help businesses set up along it.
IOHK is a private company, not a government body or a charity. It earns money from contracts and holdings related to the projects it works on. That is why people sometimes debate how independent Cardano is from the firm that built most of it.
History
After leaving Ethereum in 2014, Charles Hoskinson and Jeremy Wood set up IOHK in 2015 as a technology company working on cryptocurrency projects. Its main effort became Cardano, which launched in September 2017 after a token sale held mainly in Japan. IOHK built Cardano's first era, Byron, and led the move to proof of stake run by community pools in the Shelley upgrade of 2020. It then delivered native tokens and smart contracts during the Goguen phase in 2021, using Cardano's Hard Fork Combinator to introduce each change without restarting the chain.
Alongside Cardano, IOHK took on outside work. From 2016 it funded and ran a development team for Ethereum Classic, the chain that continued Ethereum's original history after the DAO hard fork, before later stepping back from that role. In 2021 it announced an agreement with Ethiopia's education ministry to pilot blockchain-based records for students and schools using its identity software, one of the most publicized attempts to use Cardano in government. Such projects were intended to show practical uses for the network in regions with limited banking and record-keeping infrastructure, although the long-term scale of these pilots has been hard to assess from public information.
The company rebranded from IOHK to Input Output Global around 2021 to reflect its global staff and activities beyond Hong Kong. Hoskinson has remained its chief executive and public face.
Research approach
IOHK describes its method as research-first. It published the Ouroboros family of consensus mechanisms as academic papers, many of them peer-reviewed at cryptography and computer security conferences, before implementing them. It has funded research centres and partnerships with universities, and uses formal methods and the Haskell programming language to make software easier to check mathematically. Supporters say this makes Cardano unusually rigorous; critics say it has slowed delivery compared with rival networks.
Main projects
- Cardano core software. The Cardano node, wallets, the Plutus smart-contract platform and the Marlowe language for financial contracts.
- Scaling. Hydra, a family of layer-2 protocols for fast off-chain processing.
- Identity. Work on decentralized identifiers and credentials, including pilot projects in education records.
- Midnight. A network designed for data protection and private smart contracts, linked to Cardano.
- Governance. Tools for Cardano's move to on-chain governance, in which ADA holders and elected representatives vote on changes.
Criticism and debate
IOHK has faced criticism over the pace of development, as smart contracts reached Cardano several years after Ethereum and early decentralized applications struggled with performance. Critics also argued that, for most of Cardano's history, IOHK and the other founding entities held keys needed to approve upgrades, concentrating control. The move to on-chain governance, begun in 2024, was presented as a response, shifting decisions to ADA holders. Questions have also been raised about how much of Cardano's development budget flows to IOHK, and Hoskinson's outspoken public style has attracted both supporters and critics. As with other firms in decentralized governance debates, the balance between expert-led development and community control remains contested.