Logitech K400 Plus Review: The Couch Keyboard That Still Makes Sense for a TV-Connected PC

Logitech lists the keyboard at 354.3 mm long, 139.9 mm deep and 23.0 mm high, with a weight of 380 g (Logitech technical specifications). The packaging diagram on the United States retail listing rounds those numbers to 35 cm by 14 cm and gives the weight as 390 g. The gap is small, but it is two Logitech sources disagreeing. This review uses the specification figure, because that article is the more precise document.

The shell is plastic throughout, built for a sofa cushion rather than a bag. Two details help. Logitech rates the design as spill resistant and, unusually, publishes the test condition: a maximum of 60 ml of liquid, with no immersion. An on and off switch cuts power when the keyboard vanishes behind a cushion for a week.

Logitech publishes no rigidity or durability figure for the shell, so this section carries no score.

The top row carries icons rather than plain F-key labels, and Logitech documents what every one of them does. Running from the left: back, home, switch application, menu, search, show or hide the desktop, maximize window, switch screen, media, previous track, play and pause, and next track (Logitech FAQ). Mute, volume down and volume up sit as three separate keys above the touchpad, so volume never needs a modifier.

The FN layer fills the gaps left by a board with no number pad and no navigation cluster. FN with the arrow keys gives home, end, page up and page down. FN with Insert sleeps the PC, FN with Backspace takes a screenshot, and FN with Caps Lock toggles scroll lock.

Two limits matter. The top row acts as shortcuts by default, and switching it to standard F1 to F12 behavior requires the Logitech Options application. Customization then reaches only F1 to F9 and the Insert key, so letters and modifiers cannot be remapped in Logitech's software. Options can also disable Caps Lock, Scroll Lock, Insert and the Windows key, which is a small but useful touch for a keyboard that gets handed around a room.

The touchpad is the reason this keyboard exists. Logitech gives it a 3.5 inch diagonal (Logitech technical specifications), and the retail listing puts the pad at 76 mm by 47 mm. The two figures agree with each other, because a rectangle of 76 mm by 47 mm has a diagonal of about 89 mm, which is 3.5 inches.

It does more than move a pointer. Two fingers scroll vertically and horizontally by default, and holding FN while sliding one finger scrolls in any direction. One tap clicks, two taps double click, and a two finger tap produces a right click. Tap to click can be switched off by pressing FN together with the left mouse button.

Below the yellow line at the bottom of the pad sit two physical click zones, left and right. A second left click button sits at the top left corner of the keyboard. That is the detail that makes two handed use work, because the right hand can drive the pointer while the left thumb clicks.

Logitech Options adjusts pointer speed, scroll direction, smooth scrolling and the two scroll axes. No laboratory has published tracking accuracy or pointer latency measurements for this pad, so this review does not rate its precision and no claim is made about how it compares with a laptop trackpad.

The K400 Plus is light enough to sit on a lap without becoming a weight, and its 354 mm width is close to a laptop keyboard, so both hands reach the home row while the device rests on your knees. The touchpad sitting to the right of the letters, rather than below them, is what keeps the footprint down.

The missing feature is light. There is no backlighting of any kind, which Logitech's specification article confirms with a plain entry. In a dark living room, unlit ABS legends are guesswork for anyone who does not touch type. Logitech's own retail listing points buyers who want illuminated keys toward the K830 instead.

The layout also drops the number pad. For typing a search term into a streaming app that costs nothing. For entering numbers in a spreadsheet it will grate.

Setup is a USB port and nothing else. The Unifying receiver ships in the box, and Logitech's specification lists the link as its own 2.4 GHz protocol running over USB 2.0 at full speed. There is no pairing screen, no account and no application needed before you start typing.

The dongle is the Logitech Unifying type, which Logitech designs to carry up to six compatible Logitech devices on one receiver. That helps if a Logitech mouse already occupies a port on the same machine.

The cost of that simplicity is real. There is no Bluetooth, so the keyboard cannot talk to a smart TV, a tablet or a phone on its own, and it cannot hold more than one host at a time. A free USB-A port is mandatory. Our comparison of Bluetooth and 2.4 GHz keyboard connections sets out which link suits which setup.

Logitech claims a range of up to 33 feet, which it also gives as 10 meters, and attaches the caveat that range varies with the user, the environment and the computer (Logitech product page). No independent range test for this model was found during research, so treat that number as a manufacturer figure rather than a result.

Two AA cells power the keyboard, and Logitech claims up to 18 months from them with the caveat that the figure depends on use and computing conditions (Logitech technical specifications). The cells are not rechargeable. Logitech supplies two of them in the box along with the receiver, so the keyboard works as soon as it arrives.

That choice divides buyers. A rechargeable keyboard never needs a trip to the battery drawer, and a keyboard that runs for a year and a half on two cells never needs a cable. For a device that lives beside a television and gets picked up twice a day, the second pattern is the easier one to live with. The on and off switch stretches the interval further.

Logitech also publishes a carbon figure for the product, 4.9 kg CO2e, and states that the keyboard is made with recycled plastic.

On value, the K400 Plus does one job, it needs no subscription and no account, and current buying options appear in the table on this page.