Differences at a glance
The MX Keys S (2023) keeps the chassis, scissor keys and battery life of the 2019 MX Keys. What changes: several function-row keys (dictation, emoji, mic mute), a Logi Bolt receiver instead of Unifying, and Smart Actions, which are software macros in Logi Options+. Letters, digits, modifiers and hinges are interchangeable; function-row keys are not.
The MX Keys S, announced by Logitech in May 2023, is a revision of the 2019 MX Keys, not a new keyboard. Same chassis, same scissor keys, same USB-C charging. The differences come down to three points, detailed below, and only one really matters for repair: the function row, where several keys carry other symbols.
Function row: which keys changed
This is the most visible difference. On the MX Keys S, several top-row keys carry new symbols: dictation, emoji, mic mute. It matters for repair: an F key taken from the other model clips on and works, but its legend no longer matches what the key does. Order it by the symbol printed on your own keyboard.
Receiver: Unifying vs Logi Bolt
The 2019 MX Keys uses a Unifying USB receiver, the MX Keys S a Logi Bolt receiver. They are not interchangeable: a Bolt keyboard will not pair with a Unifying receiver, and vice versa. Both keyboards also connect over Bluetooth, with no receiver at all. A lost receiver can be replaced: check the logo printed on it before ordering.
Smart Actions (software)
Smart Actions arrived with the MX Keys S. They are not a key but a feature of the Logi Options+ software: sequences of actions (opening apps, typing text, running a shortcut) that you set up and then trigger from the keyboard. There is no "Smart Actions" part to replace.
Which parts are interchangeable
For repair, both keyboards are handled the same way. Letters, digits, modifiers and the space bar are the same parts, with the same scissor hinge: an MX Keys key repairs an MX Keys S, and the other way round. Only the function row is ordered by model. A hinge on its own costs €6.99.
Verdict
For repair, the two keyboards are identical apart from the function row. For a purchase, the choice mostly comes down to the receiver (Logi Bolt on the S) and the function keys; prices vary between retailers and promotions.
FAQ
Is an MX Keys S key compatible with a 2019 MX Keys?
Yes for letters, digits, modifiers and the space bar: same profile, same hinge. Not identically for the function row, where several MX Keys S keys carry other symbols.
Does the MX Keys S have a Smart Actions key?
No. Smart Actions are a feature of the Logi Options+ software, triggered from the keyboard. No physical key carries that name.
Does the MX Keys S type differently?
No: it keeps the MX Keys scissor keys and hinge. That is what makes the parts interchangeable.
Do MX Keys S function keys fit an MX Keys?
They clip on and work, since the keyboard decides what each key does, but several carry symbols that do not match the MX Keys functions. Order function keys for your own model.