Glossary
What is a NAICS code on a government contract?
NAICS is the North American Industry Classification System. A notice names the code for that buy. Your firm’s size status is judged against the size standard for that code, not against a code you wish you had.
The code on the notice is the code that matters for that competition. A firm can list several codes in SAM.gov. Listing a code does not mean you will be competitive, and it does not mean the agency will accept you as a match.
How to choose
Pick codes that describe work you have done or can staff. Read the size standard. A dollar cap that fits one code can exclude you on another. SBA size rules are detailed. If the answer changes whether you can bid a set-aside, get it checked. This glossary is not that check.
How search uses it
In contract search, the code is a better filter than a vague keyword. Then still read the statement of work. Two notices can share a code and describe different jobs.
Industry pages, such as construction and IT services, mention codes only as examples. Confirm the code on the notice in front of you.