# SDI TDI ERDI PFI vs Catalyst Timer

The clearest difference is in-app purchases: SDI TDI ERDI PFI at none against Catalyst Timer's 1. On price, update cadence, ads and device support there is nothing between them.

Both are free to download. Catalyst Timer sells 1 one-off in-app purchase. SDI TDI ERDI PFI asks for nothing beyond the download.

Both ship on a similar rhythm, roughly every 2 months. The most recent releases landed on November 3, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | SDI TDI ERDI PFI | Catalyst Timer |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.3 (151 ratings)](https://appshunter.io/ios/app/sdi-tdi-erdi-pfi/id1608231239/reviews)** | — |
| Number of ratings | **151** | — |
| Positive reviews | 40.0% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 2 months | Every 2 months |
| Monetization | Free | — |
| Size | 58 MB | 53 MB |
| Requires iOS | **15.1** | 16.4 |
| Devices | iPhone, iPod | iPhone, iPad |
| Age rating | 4+ | 4+ |
| Developer | [ITI Holdings, LLC.](https://appshunter.io/developer/1608231241) | [CODELLA EMIL DZIUBA KRZYSZTOF GROWINSKI SPOLKA JAWNA](https://appshunter.io/developer/1685654907) |

## What reviewers say

### SDI TDI ERDI PFI

[App page](https://appshunter.io/ios/app/sdi-tdi-erdi-pfi/id1608231239)

This app serves as a comprehensive diving companion, allowing users to log dives, manage digital certifications, update personal profiles, and find dive centers and instructors globally. It also provides access to exclusive content from multiple diving agencies.

**Highlights:** Dive log with offline support, Digital certification access and sharing, Personalized profile management, Global dive center and instructor search, Access to diving blogs and videos

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

**In-app purchases:** none

**What reviewers like**

- 👍 Access to eCards
- 👍 Great resource for professionals
- 👍 Good for documenting dive information
- 👍 Informative publications
- 👍 User-friendly certification agency app

**What reviewers complain about**

- 🐛 Crashing after update
- 🐛 Very glitchy
- 🐛 Laggy, especially selecting dive sites
- 🐛 Buttons unintuitive
- 🐛 Slow manual dive loading

**Reported bugs**

- Cannot log out
- Dive logs not found after download
- App crashing after update
- Very glitchy
- Laggy, especially when selecting dive sites

**Requested features**

- iPad OS integration
- Import dive logs via spreadsheet/Google Sheets
- See dive notes in log details
- Autofill for consecutive dives/same site
- Input courses and buddies not in SDI database


### Catalyst Timer

[App page](https://appshunter.io/ios/app/catalyst-timer/id6749471956)

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

**In-app purchases (1)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Lifetime Pro Access | $9.99 | one-time |


## Frequently asked questions

### Is SDI TDI ERDI PFI free?

SDI TDI ERDI PFI is free to download, with no in-app purchases.

### Is Catalyst Timer free?

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

### Do SDI TDI ERDI PFI or Catalyst Timer have ads?

Neither SDI TDI ERDI PFI nor Catalyst Timer shows ads.

### Which is updated more often, SDI TDI ERDI PFI or Catalyst Timer?

SDI TDI ERDI PFI ships an update every 2 months, and Catalyst Timer every 2 months. Most recently, SDI TDI ERDI PFI was updated on November 3, 2026 and Catalyst Timer on October 25, 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.*