The short answer: The FAR (Federal Acquisition Regulation) is the government-wide rulebook for how federal agencies buy goods and services. The DFARS (Defense Federal Acquisition Regulation Supplement) is the Department of Defense's supplement that adds to and tailors the FAR for defense acquisitions. The DFARS never replaces the FAR — it layers on top of it. So a civilian-agency contract follows the FAR (plus that agency's own supplement), while a DoD contract follows the FAR and the DFARS and, usually, a component supplement.
If you're new to federal contracting, the alphabet soup is one of the first things that trips people up. FAR, DFARS, AFARS, GSAM, DEAR — they sound interchangeable, but they sit in a strict hierarchy, and knowing where a rule lives tells you who it binds and when. Here's the whole picture.
The Federal Acquisition Regulation is the primary set of rules governing acquisition by executive-branch agencies. It's codified at Title 48 of the Code of Federal Regulations, Chapter 1 (parts 1 through 53), and it's issued jointly by the DoD, GSA, and NASA under authority that reaches across the government. When people say "the FAR governs this contract," they mean it sets the default rules — competition requirements, contract types, clauses, thresholds, and the standard solicitation and contract language.
The FAR applies to nearly every executive-agency acquisition. Its clauses and provisions are numbered in the 52 series — for example, FAR 52.212-4 (Contract Terms and Conditions—Commercial Products and Commercial Services) — and each is prescribed somewhere in parts 1–53, meaning the FAR tells you exactly when to use it.
The Defense Federal Acquisition Regulation Supplement is the Department of Defense's supplement to the FAR. It lives at 48 CFR Chapter 2 (parts 201–253), and its part numbers deliberately mirror the FAR: DFARS Part 204 supplements FAR Part 4, DFARS Part 225 supplements FAR Part 25, and so on. Its clauses and provisions are numbered in the 252 series — for example, DFARS 252.204-7012 (Safeguarding Covered Defense Information and Cyber Incident Reporting).
The DFARS does three kinds of things to the FAR: it implements FAR policy with DoD-specific procedures, it supplements the FAR with rules the FAR doesn't cover, and occasionally it authorizes a deviation. Alongside it sits the PGI (Procedures, Guidance, and Information) — a companion document that holds non-regulatory internal procedures. The PGI is guidance, not a rule you cite in a contract.
The key mental model: regulations stack. The FAR is the base layer for everyone. Then each agency adds its own supplement on top:
So there is no such thing as "FAR or DFARS." A defense contract is governed by the FAR and the DFARS and a component supplement, all at once. A civilian contract is governed by the FAR and that agency's supplement. The supplement can add clauses, tighten a threshold, or tailor FAR language — but it operates within the FAR framework, not instead of it.
The DFARS applies when the buying activity is a DoD component: the Army, Navy, Marine Corps, Air Force, Space Force, the Defense Logistics Agency, the Defense Health Agency, and the other defense agencies. If a civilian agency — GSA, VA, DHS, Treasury — is the buyer, the DFARS does not apply; that agency's own supplement does.
One nuance worth knowing: when a civilian agency buys on behalf of DoD, or DoD buys through a civilian vehicle, the applicable supplement can follow the funding and the buying office rather than the end user. That's exactly the kind of edge case where clause selection quietly goes wrong.
This isn't academic. The FAR/DFARS distinction is what determines which clauses belong in your solicitation and contract. Some of the most consequential requirements in federal contracting live in the DFARS, not the FAR:
Put a DoD acquisition together with only the FAR clauses and you've built a defective solicitation — missing mandatory DFARS clauses that a protest, a legal reviewer, or the vendor will catch. Conversely, dropping DFARS clauses onto a civilian-agency contract puts requirements in that don't belong there. Getting the layering right is a core part of building a defensible clause matrix.
Selecting clauses by hand means walking every prescription in the FAR, then the DFARS, then the component supplement, and checking each against your acquisition's attributes — agency, contract type, dollar value, commercial status, subject matter. It's exactly the kind of rules-driven work that's easy to get almost right and hard to get completely right.
We built a free tool for it. ArcClause takes your acquisition parameters and applies the FAR and DFARS prescriptions — plus agency supplements — automatically, producing a complete, citable clause matrix with each clause tied to the section that prescribes it. You review the result with a contracting officer's judgment; ArcClause removes the mechanical work of walking the prescriptions and makes sure the DFARS layer isn't missed. It's free to use, with no account required.
The FAR is the government-wide acquisition rulebook that applies to nearly all executive agencies. The DFARS is the Department of Defense's supplement that adds to, implements, or tailors the FAR for DoD acquisitions. The DFARS layers on top of the FAR — it never replaces it.
When the buying activity is a DoD component — Army, Navy, Marine Corps, Air Force, Space Force, DLA, and other defense agencies. Civilian agencies use the FAR plus their own supplement (like GSAM or HHSAR) instead.
No. A DoD acquisition follows the FAR, the DFARS, and usually a component supplement (such as AFARS for the Army or DAFFARS for the Air Force) all at once.
FAR clauses are numbered in the 52 series (52.2xx-xx); DFARS clauses are numbered in the 252 series (252.2xx-xxxx). A 252 number signals a DoD-specific clause.
Clause selection is driven by prescriptions tied to your acquisition's attributes. ArcClause applies the FAR and DFARS prescriptions automatically and builds a complete, citable matrix — free to use.
ArcClause applies the FAR, DFARS, and agency-supplement prescriptions automatically and produces a complete, citable matrix. No login, no credit card.