On-chip debug (OCD) interfaces can provide chip-level control of a target device and are a primary vector used by engineers, researchers, and hackers to extract program code or data, modify memory contents, or affect device operation on-the-fly. Depending on the complexity of the target device, manually locating available OCD interfaces can be a difficult and time consuming task, sometimes requiring physical destruction or modification of the device.

JTAGulator is an open source hardware tool that assists in identifying OCD interfaces from test points, vias, component pads, or connectors on a target device.

From 2013 to 2023, Parallax, Inc. was the official hardware manufacturer of the JTAGulator. As of July 2025, EXPLIoT is the official hardware manufacturer and maintainer. For support, visit their project page or Discord server. To purchase a JTAGulator, visit their store.

This design is distributed under a Creative Commons Attribution-ShareAlike 4.0 International license. The JTAGulator name and logo are registered trademarks of Grand Idea Studio, Inc. The trademarks may not be used on derived works without permission.