# LineConstants vs PQDIF Viewer

The clearest difference is in-app purchases: PQDIF Viewer at none against LineConstants's 2. PQDIF Viewer also leads on update cadence (every 3 days vs every 2 months) and iOS requirement (15.6 vs 18.0). On price, ads and device support there is nothing between them.

Both are free to download. LineConstants sells 2 in-app purchases, starting at $9.99 per month. PQDIF Viewer asks for nothing beyond the download.

LineConstants ships an update every 2 months, PQDIF Viewer every 3 days. The most recent releases landed on September 12, 2026 and September 21, 2026 respectively.

## The numbers

| Metric | LineConstants | PQDIF Viewer |
| --- | --- | --- |
| Price | Free | Free |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | Every 2 months | **Every 3 days** |
| Size | 33 MB | 4 MB |
| Requires iOS | 18.0 | **15.6** |
| Devices | iPhone, iPad | **iPhone, iPad, iPod** |
| Age rating | 4+ | 4+ |
| Developer | [Sergey Gussev](https://appshunter.io/developer/1784439395) | [Russell Patterson](https://appshunter.io/developer/1723606459) |

## What reviewers say

### LineConstants

[App page](https://appshunter.io/ios/app/lineconstants/id6740081204)

**Features:** macOS Compatibility, Family Sharing

**In-app purchases (2)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Monthly | $9.99 | per month |
| Yearly | $19.99 | per year |


### PQDIF Viewer

[App page](https://appshunter.io/ios/app/pqdif-viewer/id6769140607)

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

**In-app purchases:** none


## Frequently asked questions

### Is LineConstants free?

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

### Is PQDIF Viewer free?

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

### Do LineConstants or PQDIF Viewer have ads?

Neither LineConstants nor PQDIF Viewer shows ads.

### Which is updated more often, LineConstants or PQDIF Viewer?

LineConstants ships an update every 2 months, and PQDIF Viewer every 3 days. Most recently, LineConstants was updated on September 12, 2026 and PQDIF Viewer on September 21, 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.*