Online IQ tests are not reliable and are mainly designed for entertainment and to increase traffic to particular websites. The methods used by online IQ tests vary greatly from actual, scientifically-verifiable IQ tests.
The methodology behind online IQ tests varies greatly from actual, scientifically-verifiable IQ tests, such as the Stanford-Binet Intelligence Scales and the Wechsler Adult Inventory Scale. Thus, results from online IQ tests are not a reliable means of assessing intelligence.
Actual IQ tests are professionally administered, comprised of hundreds of questions, and can take over an hour to complete. The scores of actual IQ tests are distributed along a bell curve, with 100 representing an average IQ. Test designers select thousands of people at random to take the test to develop the ranges of average, below average and exceptional IQ ranges. The results of actual IQ tests remain stable over time; an individual is extremely likely to receive the same score no matter how many times she takes the test.
Online IQ tests, by contrast, generally are very short and usually only take around 20 minutes to complete. The results are not standardized and have very little relation to actual IQ, producing results that vary greatly based on inconsequential factors.