# Substation Digital vs Underlayer

The clearest difference is in-app purchases: Substation Digital at none against Underlayer's 1. Substation Digital also leads on ads (none vs shown) and update cadence (every 5 weeks vs every 5 months). On price and device support there is nothing between them.

Both are free to download. Underlayer sells 1 in-app purchase, starting at $2.99 per 7 days. Substation Digital asks for nothing beyond the download.

Substation Digital ships an update every 5 weeks, Underlayer every 5 months. The most recent releases landed on September 13, 2026 and September 12, 2026 respectively.

## The numbers

| Metric | Substation Digital | Underlayer |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | **No** | Yes |
| Ads | **No** | Yes |
| Update frequency | **Every 5 weeks** | Every 5 months |
| Size | 42 MB | 169 MB |
| Requires iOS | **13.4** | 15.1 |
| Devices | iPhone, iPod | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [International Organization for Substations Digital Development POWER VIEW](https://appshunter.io/developer/1760809328) | [Mihail Rukavishnikov](https://appshunter.io/developer/1648782212) |

## What reviewers say

### Substation Digital

[App page](https://appshunter.io/ios/app/substation-digital/id6599860006)

**Features:** macOS Compatibility

**In-app purchases:** none


### Underlayer

[App page](https://appshunter.io/ios/app/underlayer/id6753363956)

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Premium | $2.99 | per 7 days |


## Frequently asked questions

### Is Substation Digital free?

Substation Digital is free to download, with no in-app purchases.

### Is Underlayer free?

Underlayer is free to download, with in-app purchases available.

### Do Substation Digital or Underlayer have ads?

Underlayer shows ads; Substation Digital does not.

### Which is updated more often, Substation Digital or Underlayer?

Substation Digital ships an update every 5 weeks, and Underlayer every 5 months. Most recently, Substation Digital was updated on September 13, 2026 and Underlayer on September 12, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*