# Silent Observer vs DOCS II

The clearest difference is iOS requirement: Silent Observer at 9.0 against DOCS II's 15.0. On price, update cadence, ads and in-app purchases there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Silent Observer ships an update every 34 months, DOCS II every 58 months. The most recent releases landed on September 17, 2026 and October 2, 2026 respectively.

## The numbers

| Metric | Silent Observer | DOCS II |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[5.0 (1 ratings)](https://appshunter.io/ios/app/docs-ii/id1546600318/reviews)** |
| Number of ratings | — | **1** |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 34 months** | Every 58 months |
| Monetization | — | Free |
| Size | 30 MB | 91 MB |
| Requires iOS | **9.0** | 15.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Navigate360, LLC](https://appshunter.io/developer/1562199710) | [Virtual Technology LLC](https://appshunter.io/developer/1546600320) |

## What reviewers say

### Silent Observer

[App page](https://appshunter.io/ios/app/silent-observer/id1209909707)

**Features:** macOS Compatibility

**In-app purchases:** none


### DOCS II

[App page](https://appshunter.io/ios/app/docs-ii/id1546600318)

This app automates the capture and reporting of visible emission observations for air quality compliance. It uses location data, weather, and sun angles to document opacity levels, helping users avoid costly fines. The tool generates compliance archives for regulated sources.

**Highlights:** Automated Visible Emission Observation (VEO) capture, Integration with Google Maps, compass, and inclinometers, Real-time weather and sun angle data, Opacity level documentation, Automated VEO report generation, Compliance archive creation

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Silent Observer free?

Silent Observer is free to download, with no in-app purchases.

### Is DOCS II free?

DOCS II is free to download, with no in-app purchases.

### Do Silent Observer or DOCS II have ads?

Neither Silent Observer nor DOCS II shows ads.

### Which is updated more often, Silent Observer or DOCS II?

Silent Observer ships an update every 34 months, and DOCS II every 58 months. Most recently, Silent Observer was updated on September 17, 2026 and DOCS II on October 2, 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.*