Quick Answer
Cats scratch to stretch, to mark territory and to strip the worn outer layer off their claws. It is not a habit and it cannot be trained away, so an indoor cat needs a surface that is allowed. Most homes provide only one: a tall vertical post. Cats also scratch horizontally, digging in with both front paws, and that is the direction that ends up happening on a rug or the arm of a sofa. Provide both, put them where the cat already scratches, and the furniture problem usually solves itself.
Two of the ten things Google offers to finish "cat scratcher for indoor cats" with are the same question: why do cats need scratchers, and why do cats use cat scratchers. That is worth taking seriously, because the answer changes what you buy.
Why do cats scratch?
Scratching is four behaviours at once, not one. The ASPCA lists them in a single passage: "Cats scratch during play. They scratch while stretching. They scratch to mark territory or as a threatening signal other cats. And because cats' claws need regular sharpening, cats scratch on things to remove frayed, worn outer claws and expose new, sharper claws."
Three of those four have nothing to do with the object being scratched. Stretching, marking and claw maintenance are things the cat needs to do to itself, and the sofa is only the nearest surface that works. This is why punishing a cat for scratching does not work and why removing the sofa's appeal is a losing strategy: the drive does not go anywhere.
What happens in a home with no scratching surface?
The behaviour still happens, and it lands on whatever is available. Cornell's Feline Health Center frames the whole category of indoor problems this way: "some innate, normal cat behaviors become destructive within the confines of a house".
That is the honest framing for a scratcher purchase. You are not buying an accessory or an enrichment extra. You are buying the legal version of something the cat is going to do regardless, and the only question is which surface takes it.
Vertical or horizontal? Most homes only offer one
Cats scratch in two orientations and they are not interchangeable. Vertical scratching is the stretch up the door frame with both front paws high on the surface. Horizontal scratching is digging in flat, with the paws working towards the body, and it is the one that gets done on rugs, doormats and the flat arm of a sofa.
A tall sisal post covers the first. It does not cover the second, and this is the single most common gap in an otherwise well-equipped home: the owner buys a post, the cat uses it, and the rug still gets shredded. Nothing is broken. The cat is doing the other kind of scratching and the post cannot serve it.
Cover both and the sofa stops being the compromise surface. This is also why the answer to "my cat has a scratching post and still scratches the carpet" is almost never a better post.
What makes a scratcher one the cat will actually use?
Texture
Cats have preferences and they are individual. The ASPCA's advice is to test rather than guess: "Try giving your cat posts made of cardboard, carpeting, wood, sisal and upholstery." Corrugated cardboard shreds a little under the claws, which is exactly what a scratching surface is supposed to do; sisal resists more and lasts longer. A cat who ignores one will often take to the other immediately.
Stability, and height for the vertical one
A post that moves is a post that gets abandoned after one attempt. The ASPCA is direct about it: "All cats want a sturdy post that won't shift or collapse when used. Most cats also like a post that's tall enough that they can stretch fully." Full stretch for an average adult cat means a post taller than most budget models are built, which is why cheap short posts have a reputation for being ignored.
Height is a vertical requirement only. A horizontal scratcher is judged on whether it stays put on the floor and whether it is wide enough for both front paws, not on how tall it is.
Placement, which matters more than the product
Put the scratcher where the scratching already happens. The ASPCA's instruction is to identify the furniture being used and "Place scratching posts next to these objects, as 'legal' alternatives". A scratcher in the spare room is a scratcher the cat will not find. Marking behaviour in particular is location-specific: the cat is scratching by the doorway because that is where the message belongs, and a post by the doorway will be used while an identical post elsewhere will not.
How long does a cardboard scratcher last, and can you refill it?
This is what people search for after they buy one, and the honest answer is that cardboard is consumable by design. It shreds because shredding is the function. A single-cat household will typically get months rather than years out of one, and a heavy scratcher will chew through the top layer faster.
Some brands sell replacement pads that drop into a reusable frame, which is worth looking for if you expect to keep the same object for years. Others, ours included, are sold as a single piece with no separate refill. Neither approach is wrong, but the price comparison is only fair if you count the refills: a cheaper frame with paid pads can cost more over three years than a more expensive piece that gets replaced whole.
Does a scratcher file a cat's nails?
Not in the way the phrase suggests. Going back to the ASPCA's wording, scratching removes "frayed, worn outer claws" to "expose new, sharper claws". The result is a sharper claw, not a blunter one. A scratcher keeps claws healthy and sheds the dead outer sheath; it is not a substitute for clipping if your cat needs clipping.
Our own horizontal scratcher, and what it is not
Disclosure: we sell one, so treat this section as what it is. We have tried to describe it the way we would want a competitor to describe theirs.
It is a corrugated board built like a concertina, a foldable 2-in-1 lounger at $24.95. It bends into a flat ring, an arch or a curved lounger, and a bell ball runs in the groove the fold leaves down the middle. The card is bonded with cornstarch glue in a dense honeycomb, and both ends carry magnets so two boards clip into one longer run.
What it is not: it is not a substitute for a tall post. It covers the horizontal direction, which is the one most homes are missing, and if your cat is stretching up the door frame you still need something vertical. It is also a floor accessory rather than furniture. Boxed it measures 24 x 24 x 10 cm (9.4 x 9.4 x 3.9 in) at 350 g; unfolded into the spiral it takes up considerably more floor than that number suggests, but a large cat will not stretch out full length on it the way it would on a cat tree.
The ball is doing more work than it looks. A plain cardboard pad gets used when the cat happens to walk past it; something to chase brings the cat to the object in the first place, and a cat already playing on a surface is far more likely to scratch it. That is the same logic behind rotating what is available, which the Ohio State Indoor Pet Initiative describes for toys: cats "like to have a batch of toys that can be rotated a few at a time to keep them interested".
Where a scratcher sits in the rest of the day
Scratching is maintenance, not entertainment. Solving it will stop the sofa getting worse; it will not tire out a cat with nothing to do. If the scratching arrived alongside night sprinting, over-grooming or crying at the door, that is a different problem and our guide to the signs of an understimulated cat is the better place to start. For the hours nobody is home, what to leave out while you are at work covers the other half, and interactive versus automated toys covers what to buy for it.
Frequently Asked Questions
Why do indoor cats need scratchers?
Because scratching is not optional behaviour. Cats scratch to stretch, to mark territory and to strip the worn outer layer off their claws, and an indoor cat has no tree or fence post to do it on. Without a surface that is allowed, the behaviour lands on furniture, which is the same behaviour in the wrong place rather than a different one.
Do cats prefer vertical or horizontal scratchers?
Individual cats have a preference, but most do both, and the two are not interchangeable. Vertical is the full stretch up a post; horizontal is digging in flat with both front paws, which is what happens to rugs and sofa arms. A home with only a tall post is missing the direction that causes most of the damage.
Why does my cat still scratch the sofa when it has a post?
Usually one of two reasons. Either the post is the wrong orientation for the scratching being done, or it is in the wrong room. Scratching is partly a territorial message, so placing the alternative directly next to the furniture being used matters more than the quality of the alternative.
How long does a cardboard scratcher last?
Cardboard is consumable by design: it shreds because shredding is the function. A single-cat household typically gets months rather than years from one. Some brands sell replacement pads for a reusable frame and some are sold as a single piece, so compare the three-year cost rather than the shelf price.
Does scratching sharpen or blunt a cat's claws?
It sharpens them. Scratching removes the frayed outer sheath and exposes the newer, sharper claw underneath, so a scratcher keeps claws healthy but does not replace nail clipping for a cat who needs it.
