Are adjacent 8*8 blocks connected in JPEG?

Question

JPEG

I've always thought that JPEG encodes an image by breaking it into separate, unrelated blocks of 8x8 pixels.
However, when I change one pixel in the image and save it, then in addition to the changed block, neighboring blocks may also change. This does not always happen, but the probability of this is quite high.

I do the following. I load an image (img1) and save it as a JPEG (img2). It is clear that upon subsequent opening and checking it with the original, there are slight differences. If I once again save the original image (img1) as a JPEG with the same settings, I get the same image (img2). Now I change one pixel of the original image (img1) and save it as a JPEG (img3). Here are the following options. If the changes are minor, then maybe img3==img2. Sometimes it happens that the content of the block in which the pixel has changed has changed. But, sometimes, in addition to this block, the contents of the neighboring (one or several) blocks also change. Is it possible that when encoding in JPEG, changing the original content of one block can affect neighboring blocks?

Answer 1

The color information comes in differential form, so yes, the blocks are related through color.