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Editorial Team
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Asked: 2026-05-13T13:28:59+00:00

I would like to write a C# method that would transform any title into

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I would like to write a C# method that would transform any title into a URL friendly string, similar to what Stack Overflow does:

  • replace spaces with dashes
  • remove parenthesis
  • etc.

I’m thinking of removing Reserved characters as per RFC 3986 standard (from Wikipedia) but I don’t know if that would be enough? It would make links workable, but does anyone know what other characters are being replaced here at stackoverflow? I don’t want to end up with %-s in my URLs…

Current implementation

string result = Regex.Replace(value.Trim(), @"[!*'""`();:@&+=$,/\\?%#\[\]<>«»{}_]");
return Regex.Replace(result.Trim(), @"[\s*[\-–—\s]\s*]", "-");

My questions

  1. Which characters should I remove?
  2. Should I limit the maximum length of resulting string?
  3. Anyone know which rules are applied on titles here on SO?
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1 Answer

  1. Editorial Team

    Rather than looking for things to replace, the list of unreserved chars is so short, it’ll make for a nice clear regex.

    return Regex.Replace(value, @"[^A-Za-z0-9_\.~]+", "-");

    (Note that I didn’t include the dash in the list of allowed chars; that’s so it gets gobbled up by the "1 or more" operator [+] so that multiple dashes (in the original or generated or a combination) are collapsed, as per Dominic Rodger’s excellent point.)

    You may also want to remove common words ("the", "an", "a", etc.), although doing so can slightly change the meaning of a sentence. Probably want to remove any trailing dashes and periods as well.

    Also strongly recommend you do what SO and others do, and include a unique identifier other than the title, and then only use that unique ID when processing the URL. So http://example.com/articles/1234567/is-the-pop-catholic (note the missing ‘e’) and http://example.com/articles/1234567/is-the-pope-catholic resolve to the same resource.

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