All diagnostic equipment and devices are sticked to international standarts. Here you can see below what kind of standarts are in common with allmost all vehicles. SAE stands for Society of Automotive Engineers and ISO stands for International Organization for Standardization.

SAE standards documents on OBD-II

J1962 – Defines the physical connector used for the OBD-II interface.
J1850 – Defines a serial data protocol. There are 2 variants- 10.4 kbit/s (single wire, VPW) and 41.6 kbit/s (2 wire, PWM). Mainly used by US manufacturers, also known as PCI (Chrysler, 10.4K), Class 2 (GM, 10.4K), and SCP (Ford, 41.6K)
J1978 – Defines minimal operating standards for OBD-II scan tools
J1979 – Defines standards for diagnostic test modes
J2012 – Defines standards trouble codes and definitions.
J2178-1 – Defines standards for network message header formats and physical address assignments
J2178-2 – Gives data parameter definitions
J2178-3 – Defines standards for network message frame IDs for single byte headers
J2178-4 – Defines standards for network messages with three byte headers*
J2284-3 – Defines 500K CAN Physical and Data Link Layer

ISO standards

ISO 9141: Road vehicles — Diagnostic systems. International Organization for Standardization, 1989.
Part 1: Requirements for interchange of digital information
Part 2: CARB requirements for interchange of digital information
Part 3: Verification of the communication between vehicle and OBD II scan tool

ISO 11898: Road vehicles — Controller area network (CAN). International Organization for Standardization, 2003.
Part 1: Data link layer and physical signalling
Part 2: High-speed medium access unit
Part 3: Low-speed, fault-tolerant, medium-dependent interface
Part 4: Time-triggered communication

ISO 14230: Road vehicles — Diagnostic systems — Keyword Protocol 2000, International Organization for Standardization, 1999.
Part 1: Physical layer
Part 2: Data link layer
Part 3: Application layer
Part 4: Requirements for emission-related systems

ISO 15765: Road vehicles — Diagnostics on Controller Area Networks (CAN). International Organization for Standardization, 2004.
Part 1: General information
Part 2: Network layer services
Part 3: Implementation of unified diagnostic services (UDS on CAN)
Part 4: Requirements for emissions-related systems