What is the RFA file format?
.rfa files are data files native to BIM (Building Information Modeling) software Autodesk Revit, a platform used for architectural, structural, and MEP design. A single .rfa file stores the parametric definition of a reusable 3D component - a family - that can be loaded into a Revit project (.rvt) and placed within a building model.
.rfa files divide into so-called "families", which further divide into two types: system families and loadable families. A system family is built into the Revit model and is not available outside of it; walls, floors and ceilings are typical examples. A loadable family, by contrast, describes a component stored in an external .rfa file that can be shared across projects and loaded on demand.
Within loadable families, Revit distinguishes *hosted* families - placed on a host element such as a wall (doors, windows) - from non-hosted, freestanding families (furniture, equipment). New families are authored from a template (.rft) in Revit's Family Editor. Internally, .rfa uses a Microsoft Compound File Binary (OLE2) container and is version-locked: files saved in a newer Revit release cannot be opened in an older one.
Security & safety
RISK: MEDIUMRevit families are a known supply-chain risk because they can contain malicious automation: a family can hold embedded code/keynote or, more notoriously, be paired with shared parameters and an "info center"/CAD payload - the real-world example is families and projects carrying malware (e.g. the RevitDeploy / 'family virus' and DLL-injection campaigns spread via downloaded content). Load .rfa families only from trusted sources (manufacturer sites, Autodesk's library, reputable BIM portals), keep Revit updated, and scan downloaded content. Pure viewing in the web Autodesk Viewer does not execute anything and is the safe way to inspect an untrusted family.
Format details
in a nutshellPrograms that open RFA files
Windows2 apps
Autodesk Revit
Paid File > Open the .rfa to edit it in the Family Editor, or Load Into Project to place it. Subscription product.
Autodesk Viewer (web)
Free Upload the .rfa in a browser (free Autodesk account) to view/rotate/measure it without Revit - the best free way to just look at a family. 
macOS1 app
Autodesk Viewer (web)
Free Revit has no native macOS app - use the browser-based Autodesk Viewer to view .rfa on a Mac (or run Revit in a Windows VM/Boot Camp).
Autodesk Viewer
Free Drag the .rfa onto viewer.autodesk.com to view, measure and share it - no install, works on any OS. Technical details
deep spec| File category | Parametric 3D BIM component (loadable family) |
| Developer | Autodesk |
| Container format | Microsoft Compound File Binary (OLE2 structured-storage) |
| Magic bytes | D0 CF 11 E0 A1 B1 1A E1 (OLE2 header at offset 0, shared with .rvt project files) |
| MIME type | application/octet-stream |
| Version locking | Files are version-locked; a family saved in a newer Revit release cannot be opened in an older one |
| Family classification | Loadable (component) families are saved as .rfa files; system families are built into Revit and have no standalone file |
| Hosted vs. non-hosted | Loadable families are further classified as hosted (require a host element, e.g. a door on a wall) or non-hosted (freestanding, e.g. furniture or equipment) |
| Parametric behaviour | Components define parameters, constraints and formulas so dimensions, materials and visibility can vary per placed instance |
| Family template | .rft (Revit Family Template) provides the starting environment when creating a new .rfa family in the Family Editor |
| Primary editing software | Autodesk Revit (Windows; Family Editor workspace) |
| Related project format | .rvt (Revit Project); .rfa families are loaded into .rvt files via the Load Family command |
| Interoperability | Not directly exportable from a standalone .rfa; IFC and other exchange formats are generated from within a full .rvt project |
| Internal data streams | OLE2 container holds streams including BasicFileInfo (version metadata), RevitPreview8bit (thumbnail), and proprietary parametric geometry data |
| Family Editor | Dedicated Revit workspace for authoring and editing .rfa files, with its own canvas, reference planes and parameter management tools |
| Released | 2000 (Revit; Autodesk acquired Revit Technology Corp. in 2002) |
| Specification | www.autodesk.com |
RFA conversions
Community Q&A
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