So, I had a minor disaster. This is what went wrong and how I fixed it.

We use the amazing WordPress Redirection plugin. We recently started a survey and the best way to contact the participants was by letter. We had to include a URL to the survey. Some people were mistyping the URL. For example:

/direct-payments-servey
/direct-payments-urvey
/directpayment-survery/
/directpaymentsurvey
/directpaymentssurvey

The correct URL is /direct-payments-survey/

To fix this, at 8:10am this morning, I threw up a very hasty regex redirect and went to have my breakfast, slapping myself on the back. It matches all the errors and, I thought, would catch most other typos. Here it is:

^/(directpayment|direct-payment).*

Problem is it also caught the target URL and an endless redirect ensued. The page was down for 9 hours.

After my trials a little while back trying to get to grips with not matching strings in a regex I had a good idea for how to fix it.

^/(?!direct-payments-survey)(directpayment|direct-payment).*

It was that easy. Here is the regex on regex101 as usual.

The silver lining here is that I now have a very reusable fix when I need to match something very close to the target URL. I’ve had this problem in the past and often just created a completely different URL. Even then this was not foolproof as WordPress keeps it’s own records of old URLs and redirects.