# XSpecApp vs Physics Constants Library

The clearest difference is ads: XSpecApp at none against Physics Constants Library's shown. XSpecApp also leads on update cadence (every 2 days vs every 7 months) and device support (3 vs 1). On price and in-app purchases there is nothing between them.

Both are free to download. XSpecApp sells 1 one-off in-app purchase and Physics Constants Library sells 1 one-off in-app purchase. Whichever you choose, the download price is not the number that matters.

XSpecApp ships an update every 2 days, Physics Constants Library every 7 months. The most recent releases landed on September 27, 2026 and September 20, 2026 respectively.

## The numbers

| Metric | XSpecApp | Physics Constants Library |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[3.5 (2 ratings)](https://appshunter.io/ios/app/xspecapp/id1666746288/reviews)** | — |
| Number of ratings | **2** | — |
| In-app purchases | Yes | Yes |
| Ads | **No** | Yes |
| Update frequency | **Every 2 days** | Every 7 months |
| Monetization | Free with in-app purchases | — |
| Size | 48 MB | 10 MB |
| Requires iOS | **8.0** | 18.4 |
| Devices | **iPhone, iPad, iPod** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Brian Cross, XRF Consulting, LLC](https://appshunter.io/developer/1666746290) | [ChatStick Company Limited](https://appshunter.io/developer/1165816085) |

## What reviewers say

### XSpecApp

[App page](https://appshunter.io/ios/app/xspecapp/id1666746288)

This application displays EDXRF spectra, allowing users to manually identify elements, calculate ROIs, and add annotations. It supports saving, loading, and printing spectra with detailed information. The app can also acquire spectra using a digital pulse processor via USB, Serial, or wireless connections.

**Highlights:** Manual element identification, ROI calculation for peaks, Spectrum annotations, Spectrum printing with ROIs, Save and load spectra, Acquire spectra via digital pulse processor

**Features:** macOS Compatibility

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| XSpecApp | $24.99 | one-time |


### Physics Constants Library

[App page](https://appshunter.io/ios/app/physics-constants-library/id6751224343)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Unlock All Features | $2.99 | one-time |


## Frequently asked questions

### Is XSpecApp free?

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

### Is Physics Constants Library free?

Physics Constants Library is free to download, with in-app purchases available.

### Do XSpecApp or Physics Constants Library have ads?

Physics Constants Library shows ads; XSpecApp does not.

### Which is updated more often, XSpecApp or Physics Constants Library?

XSpecApp ships an update every 2 days, and Physics Constants Library every 7 months. Most recently, XSpecApp was updated on September 27, 2026 and Physics Constants Library on September 20, 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.*