Customizing software should be as easy as using it. But most customization methods require a dramatic shift from using a GUI to writing customization scripts in a programming language.

We introduce data-driven customization, a new way for end users to extend software by direct manipulation without doing traditional programming. We augment existing user interfaces with a table view showing the structured data inside the application. When users edit the table, their changes are reflected in the original UI. This simple model accommodates a spreadsheet formula language and custom data editing widgets, providing enough power to implement a variety of useful extensions.

We illustrate the approach with Wildcard, a browser extension that implements data-driven customization on the web using web scraping. Through concrete examples, we show that this paradigm can support useful extensions to many real websites, and we share reflections from our experiences using the tool.

Finally, we share our broader vision for data-driven customization: a future where end users have greater access to the data inside their applications, and better tools for flexibly making use of that data in the context of everyday software usage.