On StackExchange.com it seems you can create filters of the forms "All questions on [these sites]" or "[this tag] on All Sites" but it's very convoluted to do "[these tags] on All Sites" and especially "[these tags] on [these sites]".

Regarding the first, it seemed logical to me to be able to type multiple tags in the tags box, but it only lets you put one tag at a time. In other words, typing php mysql would match questions tagged php or mysql. Instead it searches for php mysql as one tag. (For some reason this took me ages to figure out first time I used the filters.)

For the second, again it is possible but quite convoluted. You have to do each tag in turn, then tick the sites you're interested in over and over. Here's a simple example using php mysql on Stack Overflow and Pro Webmasters. How it should work:

  1. Type php mysql in a box to select those tags.
  2. Tick Stack Overflow and Pro Webmasters to select those sites.
  3. Click "Add rule" and save.

How it actually works:

  1. Type php in the tag box.
  2. Tick Stack Overflow and Pro Webmasters.
  3. Click "Add rule".
  4. Type mysql in the tag box.
  5. Tick Stack Overflow and Pro Webmasters again.
  6. Click "Add rule" and save.

Obviously this gets worse with more tags and sites.

And finally... after I did it the long way with a handful of tags and sites, I get an error when loading my filter (I'm assuming because there are too many "clauses" in the filter):

Oops! An error occurred while fetching questions for this filter.

Detailed information about this error has automatically been recorded, and developers have been notified.


We struggled mightily with simplifying the edit-filter UI, and yet it still has 5 radio buttons, 4 text inputs, 3 buttons, a dropdown, and literally hundreds of checkboxes. With that in mind:

"[these tags] on [these sites]" can almost always be replaced with "All questions on [these sites]". Aside from a few exceptions (such as wanting [windows] on SO & Super User, but not Home Improvement), why not subscribe to the tag you're interested in on All Sites?

Perhaps an easier way to select "All questions on [these sites]" would be useful, but we couldn't think of a simple way to include it in the UI. After selecting a tag and then checking "Just these sites", the site list is constrained to sites with that tag, and each site is shown with its tagged question count, e.g. "Stack Overflow (26756)" for [windows]. Preserving this behavior with multiple tags might be confusing.

The bug you encountered ("Oops! An error occurred while fetching questions for this filter.") is caused by your filter being very large. Unfortunately, filters don't scale to infinite, but we're working on optimizing the code such that reasonably large filters are better supported.

  • There's a use case you may not be anticipating: users who want to get into the technical details of issues and help resolve them, but are not interested in discussing design patterns or concepts surrounding these details. Such a user would like to subscribe to tags on SO or webmasters.SE, but not programmers.SE, and these will often be the same tags. The OP use case is another: web development only involves a select few tags (even less if you restrict yourself to PHP/MYSQL) across all sites where questions with those tags are posted. Similar for embedded systems, and DBAs. – darvids0n Dec 8 '11 at 0:17
  • Thanks for the response. darvids0n is correct, the reason I used [tag] on [these sites] was mainly to exclude specific sites. For example if I subscribe to the html tag, I keep getting questions appear from the Tex site, which I have zero interest in. Maybe a way to exclude certain sites from the filter would be easier, although it's pretty much the same as selecting specific sites. – DisgruntledGoat Dec 8 '11 at 15:28

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