Imposes a restriction on the source code used to solve the challenge, for example, having no numbers in the source code.

Challenges with the tag impose a restriction on the source code for an answer.

Some examples:

  • Your code is not allowed to have one or multiple specified characters in it (e.g. numbers, vowels, ...).
  • Your code is not allowed to have repeated characters in it.
  • All characters in your code have to be repeated n times.
  • Your code has to be palindromic.

Note that the tag should be used with caution -- adding to an otherwise trivial challenge does not necessarily make it interesting. Generally, a challenge should be a task of moderate complexity along with a clear, simple and relevant restriction.