Comparison

Z21 vs Shelly Smart Control

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Z21

Control your model train layout and locomotives wirelessly from your iOS device. Manage your locomotive library, program digital components, and operate switches and signals with an intuitive touch interface. Enjoy a realistic train control experience with customizable driver cabs.

Highlights
  • Wireless control of locomotives and layout
  • Manage locomotive library with images
  • Program digital components
  • Intuitive graphic interface for switches and signals
  • Downloadable driver cabs for realistic control
  • Demo mode available
Features
Read full description

Use this app to connect to a Z21 Digital Center. A demo mode is available. With this app you can manage locomotive libraries, locomotives and locomotive functions, program digital components – and of course control all locomotives with DCC- or Motorola-decoder, as easy and convenient as is only possible with touch-technology. The digital switchboard Z21 connects your model train unit and your digital locomotives with your iOS device via WLAN. This way you can control the operation on your train layout easily and conveniently from your mobile device. Model train control was never this easy and convenient: With one swipe of your hand you can scroll to your model of choice in the locomotive library. A slight touch on the headlight symbol and the front and backlights go on. A second touch, this time on the speaker symbol, and the locomotive makes a sound. Drag your finger over the speed indicator and the train accelerates. The further highlights of the Z21-App • Control your entire layout with an intuitive, graphic interface and have easy access to the entire scope of functions of your digital locomotives. • Manage your entire locomotive-library in just one application, including individual locomotive images for an ideal overview. • Control the digital functions of your locomotives with intuitive function symbols instead of complicated key combinations. • Create a blueprint of your railway system and control your switches, signals and modules with a single click. • Download driver cabs and control your locomotives from a real train driver’s point of view.

About

Shelly Smart Control

Remotely monitor and control smart home devices from anywhere, either through the cloud or your local network. Manage lights, appliances, and sensors, and create custom automation scenes. Supports Wi-Fi, Bluetooth, and LAN connectivity for seamless integration.

Highlights
  • Remote device control
  • Local network control
  • Device monitoring
  • Custom scheduling
  • Scene creation
  • Energy consumption monitoring
  • Real-time alerts
Features
Read full description

This app offers the possibility to control all Shelly devices remotely. You can monitor and control your devices from anywhere (by using the cloud option) or, if you do not want the Cloud option, you will still be able to monitor and control your devices from within your local network. Shelly devices do not need to be connected to the cloud or to send data there. The Shelly Home Automation portfolio includes a variety of relay switches, sensors, plugs, bulbs, and other controllers, all connected and controlled through your Wi-Fi network. The new Shelly Plus and Shelly Pro lines of products additionally support Bluetooth connectivity for faster device inclusion and communication, and the new Shelly Pro line offers LAN and Wi-Fi usage simultaneously. The entire Shelly portfolio is available at https://shelly.cloud/ Shelly devices are suitable to control lights, garage doors, curtains, window blinds, or other appliances, trigger actions based on certain parameters from sensor devices. Devices provide near real time notification on changes of the parameters they are measuring - energy consumption, temperature other environment values. All Shelly devices have: - Embedded Web server - Wi-Fi control and connectivity - APIs for observation and control A user account is required to access, include, and control Shelly devices through the application. Once Shelly account is registered, you can: - Connect the devices to an existing W-Fi network or use their Access Point mode locally to control other Shelly devices; - Include, manage, and operate as many Shelly devices as you need; - Configure devices and manage individual settings on every device; - Configure custom scheduling for automatic actions; - Create personalized rooms for more convenient organising and control of the devices; - Define custom Groups of devices to control multiple devices with one command within the app; - Build simple and complex scenes by combining Shelly devices to trigger certain actions in your home automation; - Monitor current and past electrical power consumption of the electrical circuit(s) and loads (for Shelly devices equipped with Power-measuring capabilities); - Build complex automation solutions for improved energy and operational efficiency; - Receive real time alerts and notifications based on your preference. Shelly devices are compatible with other widely used both local and cloud-based home automation platforms like Google Home or Alexa.

Screenshots

Z214 screens
Shelly Smart Control4 screens

Verdict

The call

The clearest difference is rating: Z21 at 3.8 against Shelly Smart Control's 3.2. Z21 also leads on iOS requirement (12.0 vs 15.0). Shelly Smart Control's advantage is in-app purchases (none vs 1) and ratings volume (87 vs 13). On price, update cadence, ads and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Both are free to download. Z21 sells 1 one-off in-app purchase. Shelly Smart Control asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Z21 holds the better App Store score, 3.8 against 3.2. That said, the two scores are not equally well evidenced: Shelly Smart Control has 87 ratings behind it against 13, so its average is the more settled of the two. Written reviews complicate that: 38% of Z21's written reviews are positive against 47% of Shelly Smart Control's, so the app with the better star average is not the one people write more warmly about.

UpkeepUpdate frequency

Z21 ships an update every 3 weeks, Shelly Smart Control every 2 weeks. The most recent releases landed on October 19, 2026 and October 20, 2026 respectively.

Scorecard6 real differences · 4 level
Z21 versus Shelly Smart Control: the parameters behind the verdict, then further details
ParameterZ21Shelly Smart Control
PriceFreeFree
Rating3.8 (13 ratings) — better3.2 (87 ratings)
Positive reviews38.3% of reviews47.3% of reviews — better
Number of ratings1387 — better
Update frequencyEvery 3 weeksEvery 2 weeks — better
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree — better
DevicesiPhone, iPad, iPodiPhone, iPad, iPod, Apple Watch — better
Requires iOS12.0 — better15.0
Further details — not scored
Size232 MB255 MB
Age rating4+4+
DeveloperModelleisenbahn GmbHSHELLY EUROPE EOOD

Customer experience

Z21

All ratings13 ratings
Positive69.2%
Neutral7.7%
Negative23.1%
Written reviews94 reviews
Positive38.3%
Neutral20.2%
Negative41.5%

Shelly Smart Control

All ratings87 ratings
Positive51.7%
Neutral9.2%
Negative39.1%
Written reviews146 reviews
Positive47.3%
Neutral13.0%
Negative39.7%

Bugs and requests

Z21

Reported bugs

17 issues
  • App crashes on startup (white screen issue)
  • Connection drops to Z21 central station
  • Throttle display shows incorrect or blank speeds
  • Function buttons not responding properly in multitraction mode
  • Route synchronization failures across multiple control station pages
Show 12 more
  • Weichen (turnout) display showing white/blank images
  • App freezes during speed adjustment
  • Export functionality crashes (PRO version)
  • Occupancy feedback not displaying (Roco 10808)
  • iOS 14+ compatibility issues
  • Slow response times and lag
  • Layout elements jumping off-screen when editing
  • Routes highlighting incorrectly or not at all
  • Password-protected bug report zip file inaccessible to users
  • Fleischmann turntable module not available
  • Bridge modules cannot be displayed diagonally
  • Data loss after app updates

Requested features

20 requests
  • Offline locomotive database access
  • Dark mode or customizable color schemes
  • Background image support for layout design
  • Turntable/rotary module support
  • Automatic event-based control (occupancy detection, crossing automation)
Show 15 more
  • Pendulum train control functionality
  • Manual route deactivation capability
  • Larger emergency stop button
  • Locomotive database sharing between layouts
  • Multi-language support (Spanish, French, Italian, Russian, Japanese)
  • Diagonal bridge module display
  • Camera locomotive integration
  • Double slip switch operation
  • Text labeling in layout designer
  • Improved signal image selection interface
  • Vehicle filtering and categorization system
  • Windows/Mac desktop application
  • Start-destination buttons for easier route control
  • Occupancy feedback module support (Roco 10808)
  • Copy and paste functionality in layout mode

Shelly Smart Control

Not enough reviews yet to summarise bugs or requests.

In-app purchases

1 purchases

Z21

One-time1
  • Z21 Full Version$17.99
None

Shelly Smart Control

No in-app purchases

Questions

Is Z21 free?
Z21 is free to download, with in-app purchases available.
Is Shelly Smart Control free?
Shelly Smart Control is free to download, with no in-app purchases.
Which has better reviews, Z21 or Shelly Smart Control?
Z21 is rated higher. Z21 averages 3.8 out of 5 from 13 ratings, while Shelly Smart Control averages 3.2 from 87 ratings.
Do Z21 or Shelly Smart Control have ads?
Neither Z21 nor Shelly Smart Control shows ads.
Which is updated more often, Z21 or Shelly Smart Control?
Z21 ships an update every 3 weeks, and Shelly Smart Control every 2 weeks. Most recently, Z21 was updated on October 19, 2026 and Shelly Smart Control on October 20, 2026.

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