Comparison

123test vs iq-test.io: which free IQ test is worth your ten minutes?

Twenty years of history and eleven languages, but the free version is a demo and the real test is paid.

Side by side

Test length and format

Length is the single biggest driver of how much a reasoning test can tell you, and it is the one specification that is easy to check before you start. Reliability rises with the number of items; the standard error of measurement falls roughly with the square root of test length. That is not a matter of opinion about which site is nicer, it is arithmetic.

123test.com runs free demo of 8–10 items; paid versions run 25 or 44 questions. iq-test.io runs thirty-three questions with no time limit, which puts both of them in the range where a broad band is defensible and a precise number is not.

The timer question matters more than people expect. A test that runs on a clock is partly measuring processing speed, which is a real cognitive ability but a different one from reasoning. If you want to know how well you reason when you are not being rushed, an untimed test answers that question and a timed one answers a blended version of it. Neither approach is wrong; they simply produce scores that are not interchangeable.

What you get without paying

This is where the two sites differ most sharply, and it is worth being precise about it rather than trading slogans.

On 123test, a demo score from a short sample of items comes free. Pro versions listed at $12.99, frequently discounted is the paid layer.

On iq-test.io, the score, the percentile, the breakdown across four cognitive domains and the accompanying explanation are all free, and there is no paid layer at all. That is unusual enough in this niche to be worth saying plainly: there is nothing to buy, so there is no incentive to hold anything back to make buying attractive.

The pattern to watch for on any IQ site is the gap between the word free in the title tag and the point at which the result appears. A test is free when the score is free. A test that is free to take and paid to see is a paid test with a long preamble.

Norms, scoring and honesty about both

An IQ score is a rank against a comparison group. Without knowing the group, the number means nothing, which makes the norms section the most informative part of any IQ site and the one most likely to be missing.

123test: publishes more psychometric detail than most, including culture-fair and classical variants.

iq-test.io publishes a methodology page covering the scoring model, the assumptions behind the score conversion and the limits of an unsupervised administration. It does not claim a representative national sample, because a web test does not have one.

Three things are worth checking on any site in this category, including ours:

• Does it name a norm group at all? Silence here is the loudest signal available.
• Does it report an error band? A site that gives you a single number with no interval is either unaware of measurement error or has decided you would rather not know.
• Does it distinguish its own takers from the general population? Percentiles calculated against people who chose to take an online IQ test are not percentiles against everyone.

Our own position on this is on the methodology page, and the short version is that a ten-item test earns a band and nothing finer.

The experience on a phone

Most people take these tests on a phone, which makes the mobile experience a practical concern rather than a design footnote. Matrix items are the hard case: they have to stay legible at 360 pixels wide without the answer options scrolling off the bottom of the screen.

123test: functional rather than modern; the oldest-looking design of the group.

iq-test.io renders its figures as vector graphics that scale cleanly and keeps answer targets large enough to hit with a thumb. In a test where a misread figure costs you an item, that is a scoring issue and not a cosmetic one.

Who each one is for

Pick iq-test.io if you want the whole result for nothing, you would rather not hand over an email address, and you want a site that documents how it arrived at your score.

Pick 123test if you want a culture-fair variant specifically, or you are not testing in english.

Pick neither if you need a result that carries weight somewhere. For a school placement, a workplace accommodation or anything legal, an individually administered test such as the WAIS or the WISC is the only route, and no online test substitutes for it at any price.