# J vs ShiftRhythm

The clearest difference is in-app purchases: J at none against ShiftRhythm's 3. J also leads on iOS requirement (12.2 vs 17.0). ShiftRhythm's advantage is update cadence (every 2 days vs monthly). On price, review sentiment, ads and device support there is nothing between them.

Both are free to download. ShiftRhythm sells 3 in-app purchases, starting at $2.99 per month. J asks for nothing beyond the download.

J ships an update monthly, ShiftRhythm every 2 days. The most recent releases landed on October 10, 2026 and October 8, 2026 respectively.

## The numbers

| Metric | J | ShiftRhythm |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[5.0 (4 ratings)](https://appshunter.io/ios/app/j-trainer/id1469085063/reviews)** | — |
| Number of ratings | **4** | — |
| Positive reviews | 100.0% of reviews | 100.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Monthly | **Every 2 days** |
| Monetization | **Free** | Free with in-app purchases |
| Size | 19 MB | 16 MB |
| Requires iOS | **12.2** | 17.0 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, Apple Watch |
| Age rating | 4+ | 4+ |
| Developer | [Heather Marriott](https://appshunter.io/developer/919616194) | [Jaeyoun Kim](https://appshunter.io/developer/6772886377) |

## What reviewers say

### J

[App page](https://appshunter.io/ios/app/j-trainer/id1469085063)

This app provides tools to structure your juggling practice sessions, including warm-up, practice, and cool-down routines. It features interval training for customized workouts and a talking timer for endurance practice, offering verbal feedback without needing to check your stopwatch.

**Highlights:** Structured practice routines (warm-up, practice, cool-down), Customizable interval training workouts, Talking timer for endurance practice, Verbal feedback for endurance contests, Ad-free experience

**Features:** macOS Compatibility

**In-app purchases:** none


### ShiftRhythm

[App page](https://appshunter.io/ios/app/shiftrhythm-shift-sleep/id6776639759)

This app helps night shift workers optimize their sleep and light exposure based on their unique roster. It provides personalized guidance for sleep, naps, and light timing to align with your body clock and manage sleep debt.

**Highlights:** Personalized sleep and nap timing, Light exposure guidance, Circadian rhythm dial, Sleep score and debt tracking, Roster presets and custom schedules, Apple Watch app and widgets

**Features:** macOS Compatibility, Apple Watch app, Vision Pro support

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly | $2.99 | per month |
| Yearly | $14.99 | per year |
| Lifetime | $39.99 | one-time |


## Frequently asked questions

### Is J free?

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

### Is ShiftRhythm free?

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

### Do J or ShiftRhythm have ads?

Neither J nor ShiftRhythm shows ads.

### Which is updated more often, J or ShiftRhythm?

J ships an update monthly, and ShiftRhythm every 2 days. Most recently, J was updated on October 10, 2026 and ShiftRhythm on October 8, 2026.

---

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