Optional line-breaking HTML entity that is always invisible

Question

I want an optional line-breaking character that is always invisible that works with the word-wrap: break-word; CSS style.

Here are some specifics. My goal is to break apart long links in reasonable places. These characters are a good place to start: -, ., _, /, \. This is not a Rails-specific question, but I wanted to share some code I'm using now:

module ApplicationHelper
  def with_optional_line_breaks(text)
    text.gsub(%r{([-._/\\])}, '\1­')
  end
end

Here's the problem with the code above: when ­ takes effect (in a table with: word-wrap: break-word;), ­ gets displayed as -. I don't want to see the -; I want a line break without any character shown.

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Answer 1

​ is the HTML entity for a unicode character called the zero-width space (ZWSP).

"In HTML pages, this space can be used as a potential line-break in long words as an alternative to the <wbr> tag."- Zero-width space - Wikipedia

The <wbr> tag also works, as mentioned by Aaron's answer. I think I prefer the HTML entity over the tag because the entity seems simpler: unicode handles it, not the web browser.