# Frequently asked questions (FAQ) ## Isn't this like ...? Who knows. I didn't do a lot of research before making this. It was fun making it. ## Can I use this in my app? Will it stay free? Yes. As long as you don't abuse it, it'll be available and free of charge. I do not plan on monetizing the service. ## What are the uptime guarantees? Best effort. ## What happens if there are multiple subscribers to the same topic? As per usual with pub-sub, all subscribers receive notifications if they are subscribed to a topic. ## Will you know what topics exist, can you spy on me? If you don't trust me or your messages are sensitive, run your own server. It's <a href="https://github.com/binwiederhier/ntfy">open source</a>. That said, the logs do not contain any topic names or other details about you. Messages are cached for the duration configured in `server.yml` (12h by default) to facilitate service restarts, message polling and to overcome client network disruptions. ## Can I self-host it? Yes. The server (including this Web UI) can be self-hosted, and the Android app supports adding topics from your own server as well. Check out the [install instructions](install.md). ## Why is Firebase used? In addition to caching messages locally and delivering them to long-polling subscribers, all messages are also published to Firebase Cloud Messaging (FCM) (if `FirebaseKeyFile` is set, which it is on ntfy.sh). This is to facilitate notifications on Android. If you do not care for Firebase, I suggest you install the [F-Droid version](https://f-droid.org/en/packages/io.heckel.ntfy/) of the app and [self-host your own ntfy server](install.md). ## How much battery does the Android app use? If you use the ntfy.sh server, and you don't use the [instant delivery](subscribe/phone.md#instant-delivery) feature, the Android app uses no additional battery, since Firebase Cloud Messaging (FCM) is used. If you use your own server, or you use *instant delivery*, the app has to maintain a constant connection to the server, which consumes about 0-1% of battery in 17h of use (on my phone). There has been a ton of testing and improvement around this. I think it's pretty decent now. ## What is instant delivery? [Instant delivery](subscribe/phone.md#instant-delivery) is a feature in the Android app. If turned on, the app maintains a constant connection to the server and listens for incoming notifications. This consumes <a href="#battery-usage">additional battery</a>, but delivers notifications instantly. ## Why is there no iOS app (yet)? I don't have an iPhone or a Mac, so I didn't make an iOS app yet. It'd be awesome if <a href="https://github.com/binwiederhier/ntfy/issues/4">someone else could help out</a>.