A round body cannot reach the apex of a 90-degree corner, and no firmware update will change that. Several makers now bolt an arm onto the problem, and they do not all extend the same part.
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Edges yes, true corners no. A round robot physically cannot reach the apex of a 90-degree corner, and the best current answer is an extending arm: the Dreame L40s Ultra is the one machine still on sale here that extends both a side brush and the mop. Expect a corner no robot fully cleans, and plan on a handheld for it.
This is the complaint that comes up more than any other once someone has lived with a robot for a month. The middle of the floor is spotless, there is a visible line of dust along the baseboard, and a gray triangle in every corner. It is worth saying plainly that this is not a fault, a firmware problem, or a sign you bought the wrong machine.
It is geometry. The suction intake sits under the middle of a circular body. Push a circle into a right angle and the nearest point of the circle stops short of the apex, leaving a triangle of floor that no part of the machine ever passes over. A side brush helps - it flicks debris out of that triangle and into the robot's path - but it is sweeping toward the intake rather than cleaning the corner itself.
What the makers actually do about it
Three approaches exist, and they are not equivalent:
A fixed side brush. Every robot on this site has one. It sweeps the edge strip toward the intake. It is the baseline, not a feature.
An extending side brush. An arm swings the side brush out past the body line when the robot detects it is running along a wall, putting bristles closer to the baseboard and further into the corner. Roborock calls this FlexiArm; Dreame builds its own version.
An extending mop. A swing-out arm carries the mop pad past the body line, so the wet pad covers the edge strip instead of stopping short. This is the rarer of the two, and it only matters on hard floors.
Extending edge hardware, models currently on sale here
Model
Extending side brush
Extending mop
Dreame L40s Ultra
Yes
Yes
Roborock Qrevo Pro
FlexiArm named, brush not described
Yes - FlexiArm edge mopping
Roborock Qrevo CurvX
Yes - FlexiArm Arc
No - Roborock states none for this model
Roborock Qrevo Curv S5X
Yes - FlexiArm
No
Dreame X40 Ultra
Yes
No - the pad is removable instead
ECOVACS DEEBOT T30S Combo
No
Yes - TruEdge adaptive edge mopping
Every iRobot, Shark, Narwal and eufy model
No
No
Taken from each maker's own product page or manufacturer listing, as recorded on that model's spec sheet. A fixed side brush is not counted as extending hardware. Where a maker describes edge cleaning without naming an extending part, it is counted as No. The Dreame X50 Ultra is absent from this table deliberately: Dreame describes no extending edge hardware for it.
The ECOVACS row is the odd one out. The T30S Combo has no extending side brush at all, and ECOVACS instead describes TruEdge adaptive edge mopping - the robot adjusts the pad's path along a detected edge rather than reaching further past the body. That is a different idea from an arm, and whether it works as well is not something either of us can tell from a product page.
The brands with nothing here
iRobot, Shark, Narwal and eufy build no extending edge hardware on any model we cover. iRobot and Shark both market edge performance - iRobot names an edge-sweeping brush, Shark names a 3D sensor - and neither extends a part past the body line. That is not a reason to avoid those brands generally; the Roomba Max 715 Pet is this site's pick for the best Roomba and the eufy Omni C20 is a pick on three other pages here. It is a decisive reason to avoid them if dusty baseboards are specifically the thing you want solved.
What an extending arm will not do
It will not clean the corner apex. It reduces the untouched triangle. It does not remove it. No maker publishes a figure for how close any of these gets, so we cannot rank them on millimeters and will not pretend to.
It will not clean your baseboards themselves. The vertical face of the trim is not a floor and nothing here touches it. If you arrived because a robot is marking your baseboards rather than cleaning them, that is a different problem - scratched floors and scuffed baseboards.
It will not help on carpet. An extending mop does nothing on a rug, and the extending brush matters less because carpet edges are usually tucked under furniture or trim rather than exposed.
It adds a moving part. An arm that swings in and out on every wall run is a mechanism, and mechanisms are what eventually fail. No maker publishes a duty cycle for one.
How we picked
Criteria first, products second. These are the things we ranked on, stated before anything is recommended.
State the geometry first. A round robot cannot reach a 90-degree apex. Every machine below reduces the untouched area rather than eliminating it, and we rank on what the maker says the hardware does.
Distinguish what actually extends. An extending side BRUSH sweeps dust out of the edge strip. An extending MOP swings a wet pad over it. These are different parts, and most makers fit only one of them.
Do not credit an edge claim with no mechanism behind it. "Edge cleaning" as a phrase, with no extending part named, is counted as nothing.
Weigh the rest of the sheet too. An extending arm on a machine that publishes nothing else is a narrow reason to buy.
No testing claims. Nobody publishes how close any of these gets to a baseboard, and we have not measured it. See how we pick.
What we did not do: test any of these machines. We do not own one, we do not have a lab, and nothing on this page is written as though we did. The full method.
Quick picks
Ranked on the published specifications below. Tap a row to jump to the full write-up.
#
Product
Best for
Max climb
Price
1
Dreame L40s UltraStates 40mm of obstacle clearing and a fully detangling brush, which covers the two problems that actually send robots back to the shop.
Roborock Qrevo CurvXThe highest published suction figure here paired with the highest published mop lift, which is the combination a mixed-floor home actually needs.
It is on this site's recommended list elsewhere and it is the skip here, because iRobot builds no extending edge hardware at any price. The Combo j9+ has an edge-sweeping side brush, which is the fixed corner brush robot vacuums have carried for twenty years - it flicks debris out of the edge and into the robot's path, and it cannot reach into the apex of a corner. Nothing in iRobot's current range extends a brush or a mop, and the same is true of every Shark, Narwal and eufy model we cover. If the visible dirt in your house is along the baseboards, this is the one problem where iRobot is not the brand to buy, however good the rest of the machine is.
Which one if edges are the problem
Edges and corners, both parts extending, with a real spec sheet behind it - the Dreame L40s Ultra. It is the only machine still on sale here that extends the side brush and the mop, and it publishes a 40mm climb height and 19,000 Pa alongside.
An extending brush on the flattest robot here - the Roborock Qrevo CurvX at a published 80mm, with a 17mm mop lift and seven of nine rows published. It extends the brush only.
The same FlexiArm brush for less - the Roborock Qrevo Curv S5X, where Roborock states plainly that the side brush reaches into corners a round body cannot. Four of nine rows published and no climb height.
A dedicated edge-mopping approach instead of an arm - the ECOVACS DEEBOT T30S Combo, with TruEdge adaptive edge mopping. No extending brush and no published climb height, which is the trade.
Edge mopping at the lowest price - the Roborock Qrevo Pro, which Roborock describes as FlexiArm edge mopping. Be clear about what you are getting: it publishes only three of the nine rows we track, it does not describe its main brush at all, and its stated 7,000 Pa is the lowest figure in Roborock's current range.
Your floors are mostly carpet - none of this is worth paying for. Go to robot vacuums for carpet instead.
Questions people actually ask
+ Do robot vacuums clean corners?
Not the apex of a square corner, and no model does. A round body pushed into a right angle leaves a triangle of floor that no part of the machine passes over - that is geometry, not a defect. Extending side brushes and swing-out mops shrink the triangle, and the Dreame L40s Ultra is the one machine still on sale here that extends both.
+ Which robot vacuum is best for edges and baseboards?
The Dreame L40s Ultra, because it extends both a side brush and the mop rather than only one, and because it publishes a 40mm climb height and a real suction figure alongside. The Roborock Qrevo Pro extends the mop for considerably less money but publishes only three of the nine specifications we track.
+ What is a FlexiArm side brush?
Roborock's name for an extending side brush: an arm swings the brush out past the robot's body line when it detects a wall, putting bristles closer to the baseboard. Roborock has also used the FlexiArm name for an extending mop on some models, so check which part a given model extends - it states a FlexiArm Arc side brush and no extending mop for the Qrevo CurvX.
+ Do robot vacuums clean along walls properly?
Better than they clean corners. The edge strip along a straight wall is reachable by a side brush, and an extending one gets closer still. A visible dust line along the baseboard after a few weeks is normal on a machine with a fixed side brush, and reducing it is the main thing extending hardware is for.
+ Does any Roomba have an extending side brush?
No. iRobot fits an edge-sweeping side brush on several models, which is the standard fixed corner brush, and it builds no extending brush or extending mop on any model we cover. The same is true of every Shark, Narwal and eufy machine on this site.
+ Will a robot vacuum clean my baseboards?
No. The vertical face of the trim is not a floor and nothing on these machines touches it. If a robot is leaving marks on your baseboards rather than cleaning them, see scratched floors and scuffed baseboards.
