# EF vs Observe.

The clearest difference is update cadence: Observe. at every 8 months against EF's every 48 months. EF's advantage is device support (4 vs 2). On price, ads, in-app purchases and iOS requirement there is nothing between them.

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

EF ships an update every 48 months, Observe. every 8 months. The most recent releases landed on October 1, 2026 and October 2, 2026 respectively.

## The numbers

| Metric | EF | Observe. |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 48 months | **Every 8 months** |
| Size | 22 MB | 29 MB |
| Requires iOS | **12.0** | 13.0 |
| Devices | **iPhone, iPad, iPod, Apple Watch** | iPhone, iPod |
| Age rating | 17+ | 4+ |
| Developer | [Keiji Matsui](https://appshunter.io/developer/365287272) | [SELECT ICT Systems SAE](https://appshunter.io/developer/1780577476) |

## What reviewers say

### EF

[App page](https://appshunter.io/ios/app/ef-ejection-fraction/id1342185936)

**Features:** macOS Compatibility

**In-app purchases:** none


### Observe.

[App page](https://appshunter.io/ios/app/observe/id6738393422)

**In-app purchases:** none


## Frequently asked questions

### Is EF free?

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

### Is Observe. free?

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

### Do EF or Observe. have ads?

Neither EF nor Observe. shows ads.

### Which is updated more often, EF or Observe.?

EF ships an update every 48 months, and Observe. every 8 months. Most recently, EF was updated on October 1, 2026 and Observe. 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.*