# ISF Watchkeeper 4 vs OPSM

The clearest difference is update cadence: ISF Watchkeeper 4 at every 10 days against OPSM's every 2 months. OPSM's advantage is iOS requirement (13.0 vs 15.0). On price, ads, in-app purchases and device support there is nothing between them.

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

ISF Watchkeeper 4 ships an update every 10 days, OPSM every 2 months. The most recent releases landed on October 24, 2026 and October 27, 2026 respectively.

## The numbers

| Metric | ISF Watchkeeper 4 | OPSM |
| --- | --- | --- |
| Price | Free | Free |
| Positive reviews | 50.0% of reviews | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 10 days** | Every 2 months |
| Monetization | Free | — |
| Size | 39 MB | 72 MB |
| Requires iOS | 15.0 | **13.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 4+ |
| Developer | [IT Energy](https://appshunter.io/developer/1406834686) | [MIMOS Berhad](https://appshunter.io/developer/875191495) |

## What reviewers say

### ISF Watchkeeper 4

[App page](https://appshunter.io/ios/app/isf-watchkeeper-4/id1517644023)

This app helps seafarers track and manage their work and rest hours, ensuring compliance with international maritime regulations. It automatically tests timesheets against STCW and MLC 2006, providing real-time alerts for non-conformities and offering a cloud-based solution for easy access and team collaboration.

**Highlights:** Automatic compliance testing, Predictive calculation engine, Real-time alerts and notifications, Live compliance status monitoring, Electronic timesheet signing, Cloud-based collaboration, Offline functionality

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

**In-app purchases:** none


### OPSM

[App page](https://appshunter.io/ios/app/opsm/id1620847697)

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

**In-app purchases:** none


## Frequently asked questions

### Is ISF Watchkeeper 4 free?

ISF Watchkeeper 4 is free to download, with no in-app purchases.

### Is OPSM free?

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

### Do ISF Watchkeeper 4 or OPSM have ads?

Neither ISF Watchkeeper 4 nor OPSM shows ads.

### Which is updated more often, ISF Watchkeeper 4 or OPSM?

ISF Watchkeeper 4 ships an update every 10 days, and OPSM every 2 months. Most recently, ISF Watchkeeper 4 was updated on October 24, 2026 and OPSM on October 27, 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.*