Purifier sounds stronger than filter and in the domestic market the two words are used almost interchangeably, which makes the label a poor guide to what a unit does. A tap mounted device is a small cartridge in a plastic body regardless of what it is called, and the only reliable way to know what it removes is the certification behind its claims.
Filter, purifier and what the certification says
There is no household rule making purifier mean something more capable than filter, and the same physical product is often sold under both words in different markets. What does carry meaning is independent certification to the recognised drinking water treatment unit standards, because a certifier publishes exactly which contaminant reduction claims were tested for that specific model. A unit certified for chlorine taste and odor is a taste filter whatever it is called. One certified for lead reduction has been tested to reduce lead. Look the model up rather than reading the front of the box.
What the format can physically achieve
A tap mounted unit holds a small carbon block, so its capabilities follow from that: reliable reduction of chlorine taste and odor, mechanical filtration down to the block's rated particle size, and whatever specific claims the certification names. What it cannot do is soften water, remove dissolved salts, remove nitrate, or disinfect. It is also small, which means capacity measured in a few hundred gallons rather than thousands, and shorter still if the household filters water that is going straight down the drain.
Fitting it to a real kitchen tap
The unit replaces the aerator, so the thread on your spout decides whether it can be fitted at all. Unscrew the aerator with a cloth to protect the finish and look: a male thread outside or a female thread inside are the standard cases, and adapters cover both. Pull out sprays, sculpted spouts and many designer taps have no usable thread and rule the format out entirely. Check before buying, since this is the most common reason a tap filter goes back to the shop.
Getting value from it
Use the diverter properly: filter what you drink and cook with, and leave the tap on unfiltered for washing up and hands. That single habit often doubles cartridge life, since the media is consumed by volume rather than by time. Write the fitting date on the body and replace on the manufacturer's rated volume, because exhausted carbon gives no warning and a warm wet cartridge held past capacity is somewhere bacteria will grow. Our faucet water filter guide compares certified units and what each is tested to reduce.
Questions people ask about faucet purifier
Is a purifier better than a filter?
Not by the name. The words are used interchangeably in marketing, and what distinguishes products is the independent certification behind their claims.
How do I check what it actually removes?
Look the model up in the certifier's published listing, which names the exact contaminant reduction claims that were tested for that unit.
Will it fit my kitchen tap?
Only if the spout has a standard aerator thread. Unscrew the aerator and check first, since many pull out and designer taps have none.
Why has my cartridge run out so quickly?
Usually because filtered water is being used for washing up as well as drinking. Cartridges are consumed by volume, so the diverter matters.