Comparison

Z21 vs Shelly BLE Debug

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 BLE Debug

Configure and manage Shelly Bluetooth Low Energy devices. Update firmware, pair your phone, and control beacon and buzzer functions. Easily locate your devices with this utility.

Highlights
  • Update device firmware
  • Pair device with phone
  • Turn beacon on/off
  • Control buzzer (if available)
  • Locate device (if available)
Features
Read full description

With this app you can setup the Shelly BLE Devices: • update the device firmware; • pair the device with the phone; • turn the beacon on/off; • turn the buzzer on/of (if available); • locate the device (if available);

Screenshots

Z214 screens
Shelly BLE Debug3 screens

Verdict

The call

The clearest difference is rating: Z21 at 3.8 against Shelly BLE Debug's 3.0. Z21 also leads on update cadence (every 3 weeks vs every 2 months) and ratings volume (13 vs 2). Shelly BLE Debug's advantage is in-app purchases (none vs 1). On price, review sentiment, 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 BLE Debug asks for nothing beyond the download.

ReceptionRating · Positive reviews · Number of ratings

Z21 holds the better App Store score, 3.8 against 3.0. That said, the two scores are not equally well evidenced: Z21 has 13 ratings behind it against 2, so its average is the more settled of the two. Written reviews complicate that: 38% of Z21's written reviews are positive against 42% of Shelly BLE Debug'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 BLE Debug every 2 months. The most recent releases landed on October 14, 2026 and October 9, 2026 respectively.

Scorecard6 real differences · 4 level
Z21 versus Shelly BLE Debug: the parameters behind the verdict, then further details
ParameterZ21Shelly BLE Debug
PriceFreeFree
Rating3.8 (13 ratings) — better3.0 (2 ratings)
Positive reviews38.3% of reviews41.7% of reviews — better
Number of ratings13 — better2
Update frequencyEvery 3 weeks — betterEvery 2 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree with in-app purchasesFree — better
DevicesiPhone, iPad, iPodiPhone, iPad, iPod
Requires iOS12.0 — better15.0
Further details — not scored
Size232 MB6 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 BLE Debug

All ratings2 ratings
Positive50.0%
Neutral0.0%
Negative50.0%
Written reviews12 reviews
Positive41.7%
Neutral0.0%
Negative58.3%

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 BLE Debug

Not enough reviews yet to summarise bugs or requests.

In-app purchases

1 purchases

Z21

One-time1
  • Z21 Full Version$17.99
None

Shelly BLE Debug

No in-app purchases

Questions

Is Z21 free?
Z21 is free to download, with in-app purchases available.
Is Shelly BLE Debug free?
Shelly BLE Debug is free to download, with no in-app purchases.
Which has better reviews, Z21 or Shelly BLE Debug?
Z21 is rated higher. Z21 averages 3.8 out of 5 from 13 ratings, while Shelly BLE Debug averages 3.0 from 2 ratings.
Do Z21 or Shelly BLE Debug have ads?
Neither Z21 nor Shelly BLE Debug shows ads.
Which is updated more often, Z21 or Shelly BLE Debug?
Z21 ships an update every 3 weeks, and Shelly BLE Debug every 2 months. Most recently, Z21 was updated on October 14, 2026 and Shelly BLE Debug on October 9, 2026.

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