Libraries began using Internet filters in the late 1990's due to community pressure and the Children's Internet Protection Act (CIPA). CIPA  is a federal law that requires all computers in a public library to be filtered if that library accepts any federal funds for computers that access the Internet or the costs associated with the connection to the Internet. It took effect on July 1, 2004.
According to the National Conference of State Legislatures , "twenty-one states have Internet filtering laws that apply to public schools or libraries." While most of these laws require publicly funded institutions to adopt Internet use policies, some mandate filters. Legislators are convinced that filters effectively protect minors from harmful, web-bourne Internet content. To the extent that filters are expensive and may pose a threat to free speech or open access, legislators (and much of the public) have decided that the protections for children outweigh any such concerns. The use of filters in libraries has increased steadily. Library Journal  reported that the percentage of libraries filtering increased from 25% in 2000  to 65% in 2005 , yet many librarians argue that filters have no place in a library.
The American Library Association fought CIPA in the Courts and took the position that "the use of filtering software by libraries to block access to constitutionally protected speech violates the Library Bill of Rights ". Some libraries chose not to install filters  and gave up CIPA funds instead. Filters were seen as antithetical to the mission of the library.
While some libraries were developing Internet policies explaining their reasons for not  using filters, other libraries  were quietly installing them. The libraries installing the filters soon found that filters alleviated many thorny problems they'd been grappling with. It turned out that filters did prevent children from bumping into unexpected and unwanted websites and advertisements. Filters served as a deterrent for public porn browsers. Libraries found that with some effort, they could implement and enforce their Internet Use policy. For the first time, libraries had a way to control how their public computers were being used. The filters didn't do the job perfectly, but the fact was, some libraries found there were many fewer Internet-related complaints from patrons after the filters were installed.
More public libraries are using filters  than are not using filters. How they are implemented varies from state to state and library to library. Some libraries filter all computers . Some libraries filter only the children's computers . Some libraries utilize filters offered at the state level . Others install them in individual branches. It can be done in any number of ways.
Filters today are powerful and feature-rich. They are a far cry from the simplistic filters that blocked an entire site because of an "offensive" word though they are still far from perfect. Today's filters are much better at evaluating content and the features provide the library with many options for how to implement them.
If your library is using a filter, it is your responsibility to do so with integrity and transparency. Work closely with patrons and staff and library boards to agree on a policy of filtering and then implement that policy. Monitor the performance of your filter, make adjustments, and work closely with your community.
Take advantage of the today's broad range of features  to provide a flexible filtering environment for your patrons. The requirement to filter may have been mandated by legislators, but the implementation of your filter need not be so unyielding.