How to flush (delete, remove, clear) the Firefox OCSP cache

Method #1: Restart Firefox.

Method #2: Go to Options->Advanced->Certificates-> Validation. Set checkbox "When an OCSP server connection fails, treat the certificate as invalid" to the opposite of what it is now, and then press OK button twice. That is sufficient to clear the OCSP cache. However, since you probably want the original setting that you just changed, go to Options->Advanced->Certificates-> Validation and set checkbox "When an OCSP server connection fails, treat the certificate as invalid" back to the value that was there before you read this post, then press OK button twice.

One instance where flushing the OCSP cache is useful is detailed at https://www.wilderssecurity.com/thr...csp_server_error-using-hard-fail-ocsp.364181/.