MasterFormat is a standard for organizing specifications and other written information for commercial and institutional building projects in the U.S. and Canada. Sometimes referred to as the "Dewey Decimal System" of building construction, MasterFormat is a product of the Construction Specifications Institute (CSI) and Construction Specifications Canada (CSC). It provides a master list of Divisions, and Sections within each Division, to organize information about a facility’s construction requirements and associated activities.

MasterFormat is used throughout the construction industry to format specifications for construction contract documents. By organizing information into distinct groups, it assists in both creating and searching through the documents. The information contained in MasterFormat is organized in a standardized outline format within 50 Divisions (16 Divisions pre-2004). Each Division is subdivided into a number of Sections.

After World War II, building construction specifications began to expand as more advanced materials and choices were made available. The Construction Specifications Institute (CSI) was founded in 1948 and began to address the organization of specifications into a numbering system. In 1963, they published a format for construction specifications, outlining 16 major divisions of work. A 1975 CSI publication used the term MasterFormat. The last CSI MasterFormat publication to use the 16 divisions was in 1995, and this is no longer supported by CSI. In November 2004, MasterFormat expanded from 16 Divisions to 50 Divisions, reflecting innovations in the construction industry and expanding the coverage to a larger part of the construction industry. Revised editions were published in 2010, 2011, 2012, 2014, 2016, 2018, and 2020.

Standardizing the presentation of such information improves communication among all parties involved in construction projects, which helps the project team deliver structures to owners according to their requirements, timelines, and budgets. The ASTM standard for sustainability assessment of building products relies on MasterFormat to organize the data. MasterFormat is an organizational component of Building Systems Design - SpecLink, MasterSpec, SpecText, National Master Specification (NMS), and SpecsIntact systems. Manufacturers will often publish specifications for their products based on MasterFormat. Design teams may maintain office master section based on MasterFormat and pull specifications from multiple sources. MasterFormat provides the overall organizational structure that makes pulling sections from different sources coherent.

MasterSpec and SpecText are specifications targeted to construction projects in the United States. NMS is targeted to construction projects in Canada. SpecsIntact is a specification processing system for preparing Unified Facilities Guide Specifications (UFGS). UFGS is required for design teams to use on United States Department of Defense and NASA construction projects. Using MasterFormat provides the design and construction teams a familiar organizational structure.

The current MasterFormat Divisions are:

PROCUREMENT AND CONTRACTING REQUIREMENTS GROUP

SPECIFICATIONS GROUP