[backslash] / can be used like this [/每] in ttrss’s filter, this can filte the “/” or “每”, but I test it in some regex tools, it tells me [/每] is not ok, I should use [\/每], So which is correct?
With [\/每], the filter in ttrss is not correct though.
Firstly you’re describing a normal slash (/), not the backslash (\).
Secondly, / is commonly used to delimit a regular expression, so indeed if you want to use one inside a regex you need to escape it (using a backslash). Yes, even if inside a [] sequence.
As to why your regex “is not correct though”. What is it you’re trying to achieve? What text is this meant to match (and not match) against ?
So just write your expression without escaping the slashes and it should work.
For testing with Regex101 you can change the delimiter to a character which is not used within your expression. Just click on the delimiter and select one.