z-Tree is a software package for developing and conducting economic experiments. It is stable and allows programming almost any kind of experiment quickly. The software is designed with simple and compact language, making it easy to develop experiments without requiring extensive programming experience. z-Tree is flexible, allowing the simple programming of normal form games, extensive form games, double auctions, or clock auctions. It supports graphical elements, such as game trees, pie charts, price paths, and network links, which can be used for input and interaction. The software also includes a chat function, allowing subjects to communicate directly on their screens. Additionally, it supports neuroeconomic applications, such as recording precise timing of screen changes and subjects' input, and input from external hardware like fMRI scanners. z-Tree is implemented as a client-server application with a server application for the experimenter and a client application for the subjects. The software handles communication between subjects' computers, data presentation, and input processing. It is stable and supports recovery after incidents. Networking is based on TCP/IP, allowing experiments to be conducted via the Internet. The software is designed to be easy to use and allows for the rapid implementation of experiments. It supports a wide range of experiments, including simultaneous and sequential games, markets, bargaining, and auctions. The software uses a stage-based structure to define experiments, allowing for the definition of any kind of game. It also supports graphical input and output, as well as free-form communication through chat boxes. Data is stored in text files and can be imported into statistical or spreadsheet programs for analysis. z-Tree is available free of charge, with the only requirement being the citation of this article when experiments are published. The software has some limitations, including delays in screen presentation and the lack of a general interface for external hardware. Future improvements include extending the programming language and increasing speed for more graphically oriented experiments.z-Tree is a software package for developing and conducting economic experiments. It is stable and allows programming almost any kind of experiment quickly. The software is designed with simple and compact language, making it easy to develop experiments without requiring extensive programming experience. z-Tree is flexible, allowing the simple programming of normal form games, extensive form games, double auctions, or clock auctions. It supports graphical elements, such as game trees, pie charts, price paths, and network links, which can be used for input and interaction. The software also includes a chat function, allowing subjects to communicate directly on their screens. Additionally, it supports neuroeconomic applications, such as recording precise timing of screen changes and subjects' input, and input from external hardware like fMRI scanners. z-Tree is implemented as a client-server application with a server application for the experimenter and a client application for the subjects. The software handles communication between subjects' computers, data presentation, and input processing. It is stable and supports recovery after incidents. Networking is based on TCP/IP, allowing experiments to be conducted via the Internet. The software is designed to be easy to use and allows for the rapid implementation of experiments. It supports a wide range of experiments, including simultaneous and sequential games, markets, bargaining, and auctions. The software uses a stage-based structure to define experiments, allowing for the definition of any kind of game. It also supports graphical input and output, as well as free-form communication through chat boxes. Data is stored in text files and can be imported into statistical or spreadsheet programs for analysis. z-Tree is available free of charge, with the only requirement being the citation of this article when experiments are published. The software has some limitations, including delays in screen presentation and the lack of a general interface for external hardware. Future improvements include extending the programming language and increasing speed for more graphically oriented experiments.