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Not suitable/safe for work (NSFW), not work-suitable/safe (NWS), or not school-suitable (NSS) is Internet slang or shorthand. Typically, the NSFW tag is used in E-mail headers, and on interactive discussion areas (such as internet forums, blogs, and community websites) to mark URLs or hyperlinks that may be sexually explicit or includes audio that contains profanity, so that the reader can avoid content that may be objectionable or avoid viewing it in a place where it may lead to embarrassment.

For example, one may tag a URL as unsafe:

http://www.example.com/sextape.html¦W_WFIXME¦(NSFW)

or could be

hxxp://www.example.com/sextape.html (Notice the xx in hxxp)

NSFW has particular relevance for individuals making personal use of the Internet at workplaces or schools that have policies prohibiting access, even inadvertently, of sexually explicit images. Companies and universities frequently adopt such policies because they regard the presence of sexually explicit images as a misuse of company property (or education resources) and, potentially, a violation of sexual harassment policy.

Determining a site to be NSFW is invariably subjective. The less frequently used warnings PNSFW (Probably/Possibly Not Safe For Work), LSFW (Less Safe For Work), and TSFW (Technically Safe For Work) are sometimes used to indicate content that may be considered salacious by particularly strict censors, such as images of underwear or swimwear models, or a news story about sexual issues that does not contain explicit images. NSFW is also sometimes used to refer to any media that produces sound, such as a game or video file, the implication being that the noises may alert others in the vicinity that the user is viewing entertainment materials instead of working.

NSFW is often sarcastically used, under the same circumstances, as a meaning for "Now Show Friends and Workmates".[citation needed]

Superseding NSFW are the abbreviations NLS and NMS, used on the Something Awful Forums, which stand for Not Life Safe and Not Mind Safe, respectively. These are typically used when referring to internet shock sites, sites promoting any form of webcest, or other highly grotesque material. Of similar use on the b3ta.com forums is NSFA, meaning not safe for anyone/anywhere.