creditcard validation - why does nit not fail for 7 digits? using luhns credit card check algorithm why is digits with 7 length allowed ?  for example 1111111 is a verfied credit card number meaningly if it has only six digits its not. this does not look like a credit card number to me, am i missing something ?

go to any online credit card validation site and try 1111111 and see that it returns valid. why ?

I have tried going to the following websites: http://www.dcode.fr/luhn-algorithm and a few others.
Luhn's algorithm, as described in Wikipedia, works for any number of digits. It will detect any single digit change and most swaps.

As for an internet website which accepts credit card numbers of the wrong length - the blame should be on the designers of the website who neglected to enforce this restriction, not on Luhn's algorithm, which performs as advertized.