✗ The myth everyone repeats
After death, hair and fingernails continue to grow, sometimes significantly, as the body decomposes.
✓ What is actually true
Hair and nails don't actually grow after death because growth requires living cells and metabolism. The appearance of growth is an optical illusion caused by dehydration and retraction of skin around the base of hair follicles and nails, making them more prominent. As the skin shrinks, nails and hair appear to have extended.
Reception
The receipts 2 sources