# Số Lạ vs PrefixBlock

The clearest difference is in-app purchases: Số Lạ at none against PrefixBlock's 3. Số Lạ also leads on iOS requirement (15.1 vs 17.6). PrefixBlock's advantage is update cadence (every 3 days vs every 6 weeks). On price, ads and device support there is nothing between them.

Both are free to download. PrefixBlock sells 3 in-app purchases, starting at $0.99 per month. Số Lạ asks for nothing beyond the download.

Số Lạ ships an update every 6 weeks, PrefixBlock every 3 days. The most recent releases landed on October 24, 2026 and October 25, 2026 respectively.

## The numbers

| Metric | Số Lạ | PrefixBlock |
| --- | --- | --- |
| Price | Free | Free |
| Rating | **[4.9 (18 ratings)](https://appshunter.io/ios/app/so-la/id6462660717/reviews)** | — |
| Number of ratings | **18** | — |
| Positive reviews | 71.4% of reviews | — |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 6 weeks | **Every 3 days** |
| Monetization | Free | — |
| Size | 36 MB | 4 MB |
| Requires iOS | **15.1** | 17.6 |
| Devices | **iPhone, iPod** | iPhone |
| Age rating | 4+ | 4+ |
| Developer | [Tuan Anh Vu](https://appshunter.io/developer/398453365) | [Phung Doanh](https://appshunter.io/developer/965062916) |

## What reviewers say

### Số Lạ

[App page](https://appshunter.io/ios/app/so-la/id6462660717)

This app identifies spam calls and displays caller ID, featuring a large blacklist of unwanted callers. It also provides a comprehensive directory of Vietnamese businesses and individuals, and allows reporting of fraudulent bank accounts. Enhanced features are available for newer iOS versions.

**Highlights:** Spam call identification, Caller ID display, Extensive blacklist, Vietnamese business directory, Fraudulent bank account reporting, Live Caller ID Lookup (iOS 18+)

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

**In-app purchases:** none


### PrefixBlock

[App page](https://appshunter.io/ios/app/prefixblock-spam-call-filter/id6800204952)

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

**In-app purchases (3)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Chặn đầu số pro tháng | $0.99 | per month |
| Chặn đầu số pro năm | $4.99 | per year |
| Chặn đầu số trọn đời | $9.99 | one-time |


## Frequently asked questions

### Is Số Lạ free?

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

### Is PrefixBlock free?

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

### Do Số Lạ or PrefixBlock have ads?

Neither Số Lạ nor PrefixBlock shows ads.

### Which is updated more often, Số Lạ or PrefixBlock?

Số Lạ ships an update every 6 weeks, and PrefixBlock every 3 days. Most recently, Số Lạ was updated on October 24, 2026 and PrefixBlock 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.*