# Castel SIP vs M1 Messenger

The clearest difference is review sentiment: Castel SIP at 60% against M1 Messenger's 0%. M1 Messenger's advantage is update cadence (every 3 weeks vs every 4 months) and iOS requirement (9.0 vs 15.5). On price, ads, in-app purchases and monetization model there is nothing between them.

Both are free to download. Neither carries in-app purchases, so what you see is what you pay.

Castel SIP ships an update every 4 months, M1 Messenger every 3 weeks. The most recent releases landed on November 1, 2026 and November 4, 2026 respectively.

## The numbers

| Metric | Castel SIP | M1 Messenger |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[1.0 (1 ratings)](https://appshunter.io/ios/app/m1-messenger/id1315569851/reviews)** |
| Number of ratings | — | **1** |
| Positive reviews | **60.0% of reviews** | 0.0% of reviews |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 4 months | **Every 3 weeks** |
| Monetization | Free | Free |
| Size | 84 MB | 79 MB |
| Requires iOS | 15.5 | **9.0** |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 4+ | 17+ |
| Developer | [Castel](https://appshunter.io/developer/566301834) | [Melliton](https://appshunter.io/developer/953108739) |

## What reviewers say

### Castel SIP

[App page](https://appshunter.io/ios/app/castel-sip/id566301831)

This application functions as a SIP intercom softphone, enabling users to make and receive audio and video calls from IP intercom stations on their mobile devices. It allows for communication and remote door opening, working through Wi-Fi and cellular data networks.

**Highlights:** Audio and video calls, IP intercom station integration, Remote door opening, Address book with favorites, Call history, Remote commands during calls

**Features:** macOS Compatibility

**In-app purchases:** none


### M1 Messenger

[App page](https://appshunter.io/ios/app/m1-messenger/id1315569851)

This app offers a versatile communication platform, combining SIP calling, walkie-talkie functionality, and location sharing. Connect with users nearby, track family locations, and integrate with IP PBX systems for broader calling capabilities.

**Highlights:** SIP client with push notifications, Walkie-Talkie mode (Push-To-Talk), Users Nearby discovery, Family Locator, PSTN/GSM calling, IP PBX integration

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is Castel SIP free?

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

### Is M1 Messenger free?

M1 Messenger is free to download, with no in-app purchases.

### Do Castel SIP or M1 Messenger have ads?

Neither Castel SIP nor M1 Messenger shows ads.

### Which is updated more often, Castel SIP or M1 Messenger?

Castel SIP ships an update every 4 months, and M1 Messenger every 3 weeks. Most recently, Castel SIP was updated on November 1, 2026 and M1 Messenger on November 4, 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.*