Key Filter Features

When shopping for a filter, there are a few key features to keep an eye out for, IMHO. Here they are:

1. Customizable Block Page
   The page that comes up when a patron encounters a blocked page is their first exposure to the filter so it is important to make the experience as positive as possible. Lots of filters allow for a good deal of flexibility on the block page. I recommend -- at the very least -- that you include the URL of the site that is blocked as well as the category that caused the block. In addition, be sure to tell the blocked patron what their options are: how they get the page unblocked, how do they turn off the filter, where do they go for help, why is there a block at all???!! -- use the block page to provide this type of useful information.
2. Flexibile Override Features
   It is important to decide whether you want to be able to override a single blocked page by walking up to the patron's workstation or if you'd rather allow patrons to submit a request anonymously. Different products provide very different ways to override blocked sites. Look for the product that allows you to do it the way you want to do AND which offers some key flexibility such as being able to set the amount of time the override will be in effect and the extent of the override - does it apply to the individual page, the entire domain, the entire category that caused the block, the entire filter.
3. Accurate Block List
   Make sure the list of sites your library is blocking is really what you say it is. If you are using a product that doesn't allow you to see the URLs in the categories you are blocking, then it is important to monitor the block list to make sure you aren't blocking more sites than you think you are. Using your own block list, with sites you are sure you mean to block, is the best way to ensure you are not blocking content beyond what your IUP states.
4. Feedback from Patrons
   Some filters make it easier to gather feedback from the patrons about how the filter is working for them. Perhaps you can use the block page to give patrons the option to ask you to review how a site was categorized or blocked to see about changing it....or if not through the filter, design a Filter Feedback Form that allows patrons to comment on how the filter is working. Give them the chance to anonymously tell you about sites that were blocked that they wished hadn't been, and visa versa.
5. Ability to Manage Categories
   If you are using a product that gives you a list of categories to choose for blocking, you need to have a way to manage those lists. Inevitably, some sites are going to be blocked that shouldn't be because the filter made a mistake. Some sites are going to blocked that you don't think should have been because you disagree with the filter company's assessment of the page. Look for products that allow you to view URLs in each category, add your own categories, move URLs from one category to another and rename the categories.
6. Ability to "Disable" the Filter
   Make sure you have a way to turn off the content filter so that when an adult requests free access, you can oblige in a way that is consistent with your Internet Use Policy. This might mean that you don't actually disable the filter entirely but you unblock the categories are are benig blocked based on content. In other words, you might want to keep the filter running so that other activities are not allowed such as chatting or Internet game-playing (if you don't allow such activities on your library computers) but you'll need a way to unblock any constitutionally protected speech for adults who ask you to. A good, flexible override feature can do this for you -- this is a better approach to the "request to turn off filtering" then simply disabling the filter entirely and then worrying about how to get it turned back on later.
7. Good Reporting Tools
   A filter that allows you to easily generate key reports is going to make the job of monitoring your filter a whole lot easier. At the very least, look for filters that can generate a list of all the sites that have been blocked with the categories that caused the block. This is the best way to see how well your filter is working. And if you are maintaining your own block list, you'll need to also scan the accessed sites too, to see if there are any pages being accessed that belong on your block list. Good reporting tools can be a life-saver, but be sure to regularly purge logs and only maintain reports that summarize the data. Be very careful about protecting patron privacy by purging any data that can be tracked back to any individual patron.