Where is the compression quality stored in a JPEG file?

Question

JPEG

Some programs (usually viewers) can show what the original quality was when resaving a JPEG. Moreover, many make a reservation "to offer a similar quality when possible." Is there such a field in the file and where is it located, or do some image programs calculate this parameter from the data of the image itself, and this value is not actually stored anywhere?
I re-read a bunch of sites, but I still can’t understand if this value is saved in the file?

Answer 1

Quality is not stored anywhere, because each program has its own quality parameter. For some it's 0-100, for photoshop it's 1-12. That is, this is only a certain indicator of better or worse, nothing more.
Most likely, these programs are evaluating the file size, and such compression parameters are selected so that this size is approximately the same.