Why? My experience with them was pretty bad. I took their assessment for web development, I think I even did an assignment, and got put on a video call with someone from Triplebyte. He never cracked a smile. Suddenly I got asked a bunch of CS questions that really were not very relevant to web development, some of which were entirely inappropriate like sorting a binary search tree. I even told the guy that I thought I was getting those questions wrong and he just scowled and said "well you just don't know when you're going to use this stuff." "My point exactly," I thought.
Ultimately I got rejected.
The whole idea that you can boil down a candidate to some coding challenges and a video quiz is bad. I do like the idea of streamlining the hiring process for developers, but there's more to it than knowing a bunch of stuff, because that can be gamed. And quizzing me on irrelevant material was a bad move. A firm like Triplebyte won't be as good at interviewing a candidate as the employer itself, and may even keep perfectly qualified candidates out of view from all employers affiliated with them.
I started using them about a year ago (first passively looking, then actively looking)
I really enjoyed the ability to be assessed on something besides Leetcode style questions.
I didn't take a job through their platform (though I did get one really strong offer), but even still, found the assessments incredibly useful, since they give you a percentile distribution of your performance for each topic-specific test.
After taking their assessments, when interviewers asked me how I am at, say, Python, I could tell them I have a hard time assessing my capabilities. "But hey, I took this standardized test that says I'm in the 85th percentile, not sure how good of a metric it is" (and not mentioning that I think I'm OK at best, at Python)
It's the only way I've found to get a measure of your talents compared to the rest of the field (even if it might not be reliable/useful)
A lot of the companies that interview through Triplebyte also skip LC mediums because they have a different signal about your potential suitability as a candidate.
Way too much of engineering is non-quantifiable. Putting a number to someone's skills is bound to be reductive at best.
Like honestly I might think I'm a 3 at X, but if some test that thousands of other people took tells me I'm in the 90th percentile of X users, that information is still useful to me.
One complaint I do have is that (in addition to the percentile bucket) they give you a 1-5 rating, where 4 is "senior engineer level" and 5 is something "exceptional performance, a leader in the field"
But the ratings seem to fall at different percentile distributions for each test.
For example, I might get 80th percentile on one test, but get a 3 rating, and for another test, 80th percentile is a 5.
In general, different quizzes have vastly different populations of people attempting them. For example, our front-end quiz gets a lot of beginners and hobbyists, and thus has a very bottom-loaded score distribution. Our devops-related quizzes, on the other hand, have a population that skews skilled and senior, and has a very top-loaded score distribution.
Communicating this information to our users (particularly the less-quantitatively-oriented ones on the company side) has been a source of considerable UI challenges for us.
Personally speaking, I've used Python a handful of times over the years, but never as a primary language for any work I've done. I got a 4 on the Python test.
Compared to front-end, which I've been using professionally, and also dabbling in for ~20 years (still keeping up with developments in the years in which I wasn't primarily doing front-end dev professionally)
I got a 3.
I definitely know 100X as many random facts about front-end APIs, libraries, tooling, and technologies than I do about Python. So perhaps it just came down to luck (guessed unlucky for the front-end and lucky for Python). Or perhaps there's just so much more to know that falls in scope for the front-end quiz than there is for Python, to the point where you can spend 20 years learning the front-end technologies and still be "middle-of-the-road" in terms of "absolute level of skill".
But I think that makes your descriptions of the 1-5 rankings a bit disingenuous. If people who has (what most other companies would consider) senior-level knowledge is generally considered a 3 by your system, a more honest ranking of the descriptions would involve changing "4: level expected of seniors" to "4: knows roughly ~80% or more of all things there are to know about this subject".