Legitimate instruments can be found on the web (see section above for examples), but there are many others posted as well. Commercial publishers such as those listed in this guide under Test-Related Companies may provide information about instruments they publish and distribute, and even sell them over the web to qualified persons. These publishers will not, however, make actual instruments available on the web because the validity of the instruments could be compromised by widespread access. In addition, improper administration and interpretation of these instruments by unqualified persons could result in harm being done to subjects.
Review any instrument found on the web carefully to ascertain its source, i.e., who put it there and who created it. An instrument might be posted by a third party, without the knowledge or permission of the author and/or publisher. Sometimes a partial or otherwise modified version of a published instrument is posted, also without the prerequisite permissions. Both of these scenarios are probable illustrations of copyright violations. Every researcher is obligated to obtain and use measurement instruments and related materials in an ethical and lawful manner.
Lots of unpublished instruments also may be found on the web. Prior to adopting such instruments for one's own use, review the parent website carefully for any requirements regarding usage and attribution. Some researchers place instruments they developed on the web to get them "out there" where they are easily accessible. Thus the web serves as publicity vehicle for instruments that are new or not very well-known and probably have been the subject of little or no research. Easy access to instruments means more people might adopt them for research use, but do so absent of much (if any) evaluative literature about them. The flip side is that use of such instruments will lead to their evaluation and perhaps, eventually, a pertinent body of professional literature. Placing instruments on the web also allows the authors themselves to monitor the websites, providing a rough gauge of the level of interest in the instruments.
A final cautionary note...Many of the instruments accessible via the web were created by people who have no training or background in the measurement or subject fields. These measures are intended strictly for entertainment purposes. They may sound legitimate and closely resemble the "real thing"--but don't be fooled!
Related reading: FAQ: Maintaining Test Security in the Age of Technology (Prepared by the APA Committee on Psychological Tests and Assessment, 2017)