For most people on regulated municipal water, a filter is optional, not a safety need.
The decision should start with data: your supplier's annual water quality report, plus a lead test in pre-1986 homes, which the EPA prices at $20 to $100 through certified labs. Filters earn their place for lead, where no exposure level is safe; for local contaminants like PFAS, which the EPA says persist in water worldwide, where reverse osmosis and certain carbon filters work; and for taste. Match the filter's certification to the actual contaminant, since no filter removes everything.
What to do
Common questions
Do I need a water filter?
Probably not for safety, possibly for a specific problem. US tap water is regulated and monitored, and the free route to knowing yours is your water supplier's annual water quality report, which lists exactly what was found in your water. Filters become worth it in defined situations: first, lead risk in older homes, where the EPA says no level of lead exposure is safe and a filter certified for lead removal is a real solution while plumbing waits; second, specific contaminants of concern in your area, like PFAS, the persistent chemicals the EPA says are found in water, air, fish, and soil across the world, where certain filter types, like reverse osmosis and some carbon filters, are the effective ones; third, taste and smell, which is legitimate but means a basic carbon pitcher does the job cheaply. The trap to avoid: buying an expensive system for a problem your water does not have. The sequence is data first: read your supplier's report, test for lead if your home is pre-1986 (the EPA puts certified lab testing at $20 to $100), then match the filter certification to the actual contaminant, because no filter removes everything and the certification mark tells you which claims were verified.