Robot Vacuum S40
2 independent reviewsRead the findings →A cheap Xiaomi robot vacuum that maps your home and drags a simple damp cloth. It's a good first robot for keeping dust and pet hair down. You empty it and wash the cloth yourself, and it won't spot cables.
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What reviewers found
Two home tests: Can Buy or Not over two weeks in a 68m² home, and Teszt Plussz in an 80m² flat, on a unit it bought itself. Both found it cleans far better than its price suggests and rarely gets stuck. Both also found hair wrapped round the brush despite Xiaomi's anti-tangle claim, and neither trusts it with cables. Rugs are where they differ: Can Buy or Not warns it will wet them, while Teszt Plussz points to app settings that keep it off them.
Can Buy or Not, hands-on, 2 weeks at home, Sept 2025 (tested on the Singapore-market S40) · Teszt Plussz, hands-on, Jan 2026
Hard floors
Reviewers rate it highlyCan Buy or Not checked its floors with a laser-lit stick vacuum and found them pretty clean after a run, and Teszt Plussz called the vacuuming effective, with the side brush getting within a centimetre of walls.
Carpet and rugs
Not enough evidenceOnly Teszt Plussz judged carpet, finding it worked very well on rugs as well as hard floors. No other review we use has tested carpet yet.
Pet hair
Mixed resultsTeszt Plussz found it cleared cat hair and human hair from the floor, but both it and Can Buy or Not found hair and fur wound round the brush despite Xiaomi's anti-tangle claim, so plan to clear it regularly.
Mopping
Mixed resultsTeszt Plussz found the fixed cloth a damp wipe rather than a mop, fine for fine dust but not stains. Can Buy or Not warns it has no carpet detection and will wet rugs unless you lift them or set rules in the app.
Navigation and obstacles
Mixed resultsBoth found it rarely got stuck, and Can Buy or Not saw it avoid chair legs and larger objects. But Can Buy or Not had a USB cable chewed and broken, and Teszt Plussz says it doesn't detect cables, cat toys or glasses.
App and software
Not enough evidenceOnly Teszt Plussz judged the app, finding the Xiaomi Home controls far more extensive than expected at this price. No other review we use has assessed it.
Noise
Not enough evidenceOnly Teszt Plussz judged noise, finding it very quiet and not unpleasant even in Turbo. No other review we use has checked it.
Reliability and support
Not enough evidenceNone of the reviews we use has run it long-term. Teszt Plussz found Xiaomi's spare parts easy to get in Hungary, but that's one review.
Value
Reviewers rate it highlyCan Buy or Not found it gets the job done for a budget price and calls it a perfect starter robot, and Teszt Plussz, which bought its own, rated its value for money unbeatable in the entry-level class.
Verdicts come from independent, hands-on, finished reviews. An area needs at least two of them before we say more than “Not enough evidence”. We don't score robots ourselves. How this works
Cleans well for the money
Can Buy or Not checked its floors with a laser-lit stick vacuum and found them pretty clean after a run, with plenty in the bin. Teszt Plussz called the vacuuming effective on both hard floors and carpet. It picked up about 95% of larger cat-litter pieces, cleared cat hair and human hair from the floor, and got to within a centimetre of walls. For everyday dust and pet hair, it does the job.
Pick up cables first
Can Buy or Not found a USB cable chewed and broken after the S40 ran over it, though it avoided chair legs and larger objects. Teszt Plussz says it doesn't detect cables, cat toys or glasses, and bumps furniture gently and often. Neither found it stuck: Can Buy or Not almost never came home to a stranded robot, and it climbed out of a bathroom 2cm lower than the hallway.
Hair wraps round the brush
Xiaomi advertises anti-tangle brushes, but both tests found otherwise. After two weeks, Can Buy or Not found curled hair and fur wound round the roller, and Teszt Plussz saw much of the hair and fur wrap round the brush, which it says cuts efficiency. Can Buy or Not says cleaning didn't suffer over its two weeks. Either way, make clearing the brush part of your routine, especially with pets or long hair.
The mop is a damp wipe
Teszt Plussz describes the fixed cloth as damp wiping rather than mopping: fine for fine dust, not for stains. It was frugal with water, with 65% left after a run on the middle setting, and Can Buy or Not had more than 70% left on the lowest. Can Buy or Not warns that without carpet detection it will wet rugs, so lift them or set carpet rules in the app, as Teszt Plussz suggests.
Teszt Plussz reviewed in Hungarian; its findings are summarised here in English. Can Buy or Not tested the Singapore model. This page covers the S40, not the S40C or S40 Pro.
Our take
Should you buy the Robot Vacuum S40?
Best for: Homes wanting everyday pet hair pickup on a small budget. Skip it if: You want the robot to empty its own dust bin.
Buy the S40 if you want a first robot that keeps dust and pet hair down on a small budget, and you're happy to pick up cables and do a little upkeep. If you want a proper mop, the S40 Pro is the better Xiaomi. If you'd rather not empty a bin, look at a self-emptying model like the Tapo RV30 Max Plus.
The S40 is the middle of Xiaomi's charge-only S40 range: more suction and a bigger battery than the S40C, but none of the spinning pads or extending arms of the S40 Pro. It maps your home with a spinning laser, cleans room by room, and drags a damp cloth behind it if you fit the water tank.
Everything else is manual. The base only charges, so you empty the bin, refill the tank and wash the cloth. It doesn't lift the cloth for rugs either, so you tell it where they are in the app.
The names are easy to mix up. The S40C looks almost identical but has half the suction and a much smaller battery, and the S40 Pro is a different robot with spinning pads. Reviews of those two don't apply here, and each has its own page.
Before you buy
The questions people ask about this one
Can it keep the mop off rugs?
Not by itself. Can Buy or Not found it has no carpet detection, so it will wet rugs when mopping. Teszt Plussz points to app settings that let you mark carpets and choose to avoid them. Set that up, or roll rugs away, before a mopping run.
Will it avoid cables and pet mess?
No. Can Buy or Not had a USB cable chewed and broken, and Teszt Plussz says it doesn't detect cables, small toys or glasses. It has no camera, so treat pet mess the same way and clear the floor first.
How often do I have to empty or refill anything?
The 520ml bin lasted three or four days for Teszt Plussz and about a week for Can Buy or Not, but check it after each run and empty as needed. The water tank holds 270ml, per the specifications. Wash and dry the cloth after mopping, refill as needed and check the brush for the hair tangles both reviewers reported.
Can it cross rugs and raised thresholds between rooms?
Doorway thresholds up to 2cm are claimed, per the specifications, and Teszt Plussz had no trouble with 2cm thresholds. Can Buy or Not saw it climb out of a bathroom 2cm lower than the rest of the flat. Teszt Plussz found carpet vacuuming good too.
Is it loud?
Not really. Teszt Plussz found it very quiet, and not unpleasant even in Turbo, though the body rattles slightly over tile grout lines. Neither test gives a measured noise figure.
Alternatives
Other robot vacuums to compare.
Q7 M5 / M5+
Why consider it: Another low-cost mapping robot that vacuums and lifts pet hair far better than its price suggests.
The compromise: It bumps into clutter too, and its charge-only dock means you empty the bin yourself.
RV30 Max Plus
Why consider it: A low-cost robot with laser mapping and a compact dock that empties the bin.
The compromise: Fine grit and sticky spills beat it, and mopping is only a clip-on pad.
D10 Plus Gen 2
Why consider it: A cheap mapping robot that empties itself into a bag for up to three months and is very good on hard floors.
The compromise: It's weak on thick carpet and runs over cables and socks.
Specs
Full specifications
Each specification names its source. Manufacturer claims are not independent test results; unconfirmed figures are labelled.
Owner reviews
Do you own the Robot Vacuum S40?
Tell people how it’s held up: cleaning, maintenance, faults and support. Owner accounts are shown separately from independent reviews.
Sources
Where this page’s findings come from
Editorial reviews
- Can Buy or Not: Xiaomi Robot Vacuum S40 review: Clean job ↗Hands-on, 2 weeks at home · Tested on the Singapore-market S40
- Teszt Plussz: Xiaomi Robot Vacuum S40 teszt ↗Hands-on
Sources
Videos
- Tothepoint Tutorials2: Xiaomi Robot Vacuum S40 Review IMPORTANT Things To Know ↗
- Family Pop TV: Xiaomi Robot Vacuum S40 Performance Analysis: Suction, Navigation, and Surface Limits ↗
- Search YouTube for Xiaomi Robot Vacuum S40 ↗Search results may include company demonstrations or similar models. Check the source and model name; a demonstration is not an independent performance test.