# ECHO vs SudokuOS

ECHO and SudokuOS are too close to call on the numbers: across 7 compared parameters — price, update cadence, ads and in-app purchases among them — neither pulls far enough ahead to decide it. What separates them is feature set and interface, not measurable difference.

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

ECHO ships an update every 3 days, SudokuOS every 4 days. The most recent releases landed on October 31, 2026 and November 8, 2026 respectively.

## The numbers

| Metric | ECHO | SudokuOS |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.0 (4 ratings)](https://appshunter.io/ios/app/echo-time-loop-puzzle/id6791749935/reviews)** | — |
| Number of ratings | **4** | — |
| Positive reviews | — | 71.4% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | **Every 3 days** | Every 4 days |
| Monetization | Free | Free |
| Size | 3 MB | 10 MB |
| Requires iOS | **17.0** | 18.0 |
| Devices | iPhone | **iPhone, iPad** |
| Age rating | 4+ | 4+ |
| Developer | [Lucas Hesseldieck](https://appshunter.io/developer/6788079537) | [Seidelapps](https://appshunter.io/developer/6819037694) |

## What reviewers say

### ECHO

[App page](https://appshunter.io/ios/app/echo-time-loop-puzzle/id6791749935)

This puzzle game challenges you to cooperate with recordings of your past actions. Solve intricate levels by coordinating with your "echoes" to overcome obstacles and complete complex sequences.

**Highlights:** Time-loop gameplay, 100 campaign levels, Daily puzzles, Endless Zen mode, Time challenge mode, Offline play, Live synthesized music

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

**In-app purchases:** none


### SudokuOS

[App page](https://appshunter.io/ios/app/sudokuos/id6819037692)

Solve Sudoku puzzles with five difficulty levels on your iPhone or iPad. Utilize notes, candidates, hints, and an erase function. Track your progress with ratings and charts, and enjoy automatic saving for uninterrupted gameplay.

**Highlights:** Five difficulty levels, Notes and candidate filling, Hint and erase functions, Progress tracking and rating, Automatic game saving, Customizable accent colors and haptics

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

**In-app purchases:** none


## Frequently asked questions

### Is ECHO free?

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

### Is SudokuOS free?

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

### Do ECHO or SudokuOS have ads?

Neither ECHO nor SudokuOS shows ads.

### Which is updated more often, ECHO or SudokuOS?

ECHO ships an update every 3 days, and SudokuOS every 4 days. Most recently, ECHO was updated on October 31, 2026 and SudokuOS on November 8, 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.*