The ”cracking” that happens with general spinal manipulation is not dangerous. It is actually nothing more than the odd sound that fluid makes when it moves suddenly within the joints of the spine.
That said, we don’t crack the neck.
The reason is that many so-called “adjustments” that we see are not done correctly. In my opinion, when it comes to determining the degree and direction of misalignments in the neck, “going by feel” without doing any diagnostic tests is insane! It is one of the reasons that we used specific x-ray analysis and nervous system testing (paraspinal thermography) to determine what-and-when we need to give an adjustment.
The problem that I see with many “adjustments” is that they are not actually done in a way that corrects the misalignment. As a result, you can still have a “cracking” or “popping” noise, but no genuine change. The result is that the ligaments that support the neck can become over-stretched, which increases the chance of future injury,
The way that we adjust the neck - wit the head in a neutral position - is designed based on the results of your tests, and at the angle that requires the least amount of force. It is the reason that there is no actual “crack” at all with the type of upper cervical specific adjustments we perform.
So it is not the “cracking” sound that guarantees that an adjustment works. Conversely, just because there is a “cracking” sound does not mean that the vertebrae moved the right way either.
There is a time when a physical adjustment that causes a “cracking” sound is quite appropriate. I would simply want to be 100% sure that the procedure being done is congruent with the results of your tests, and that will biomechanically achieve what it is meant to do.