Frequently Asked Questions
Everything you need to know about Holos

school Basic Concepts

What is the Fediverse?
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The Fediverse is a decentralized social network made up of thousands of independent servers (Mastodon, Pleroma, Misskey, etc.) that communicate with each other via the ActivityPub protocol. You can follow and interact with users on any compatible server, just like you can send emails from Gmail to Outlook.
What is Holos?
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Holos is a unique Fediverse client where your device is your own ActivityPub server. Unlike traditional apps that connect to a remote server (like Mastodon), Holos stores your data, cryptographic keys, and followers directly on your device. However, your identity remains tied to the relay's domain (@you@holos.social), unless you configure your own domain via a CNAME record.
What is the relay for?
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The relay solves a fundamental problem: personal devices don't have stable internet addresses. The relay provides a permanent identity (@you@holos.social) and forwards requests to your device when it's online. It also caches your profile and public posts so they remain accessible even when you're offline.
How is Holos different from other fediverse apps?
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With a traditional fediverse client, your data lives on a remote server managed by someone else. They have permanent access to all your data and can delete your account or shut down the server.

With Holos, your device IS the server. Your data, keys, and followers stay on your device. The relay only acts as a mailbox and cache. You can switch relays, use your own domain, and nobody can access your private data.

The trade-off: you need the app installed (no web interface), and you rely on a relay for reachability when offline.

Is Holos free?
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Yes, Holos is completely free and open source (AGPL-3.0). There are no ads, no premium plans, and no data monetization. The relay at holos.social is provided at no cost. If you want full independence, you can self-host your own relay.

touch_app Daily Usage

What happens when I'm offline?
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When you're offline, the relay temporarily stores activities meant for you. Each activity type has a different retention time (TTL):

  • Follow requests: 365 days
  • Direct messages: 30 days
  • Mentions: 14 days
  • Posts and others: 7 days

You can reduce these durations in the app settings (between 0 and the server maximum). As soon as you come back online, activities are synced to your device. They expire automatically from the relay when their TTL is reached.

How do I follow someone on another instance?
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Simply search for their full identifier (e.g., @user@mastodon.social) in the search screen. Holos will resolve the address and you can follow them like any other user. The Fediverse allows communication between all ActivityPub-compatible instances.
Does Holos drain my battery?
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When you close the app, the connection is cut and the relay queues incoming activities. Nothing runs on your device until you come back.

When you reopen the app, it syncs the queued activities. You can also enable push notifications to wake the app on important events (DMs, follows, mentions) without keeping a permanent connection.

In short: your device is only active when you use it or when a push notification wakes it briefly. No background server running 24/7.

Does it use a lot of mobile data?
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Holos is designed to be data-efficient. Text activities are tiny (a few KB). Media (images, videos) are loaded on demand and cached. The relay handles delivery fan-out to your followers, so your device doesn't need to contact each one individually.
Is there a web interface?
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No. Since your device is the server, you need the app installed to use Holos. There is no web client. Your public profile and posts are visible on the web (anyone can see them via your relay URL), but posting and interacting requires the app.
How do I discover new people to follow?
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Several ways:

  • Search: Search by handle (@user@instance.social), hashtag, or keyword
  • Holos Discover: A dedicated fediverse search engine at discover.holos.social
  • Hashtags: Follow hashtags to see all public posts using them
  • Profiles: Browse someone's followers/following lists to find interesting accounts
How can I moderate my experience?
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Holos offers several tools to control your experience:

Account actions:

  • Block: The user will no longer be able to see your content or interact with you. This action is federated (visible to other servers).
  • Mute: You will no longer see this user's posts, but they can still follow you and see your content. This action remains local.
  • Report: Sends a report to moderators. Choose a category (spam, rule violation, other) and add a comment if needed.

Timeline filters:

  • Hide boosts
  • Hide replies
  • Filter by language
  • Filter by keywords or phrases (hide posts containing certain terms)
  • Automatically show/hide sensitive content and warnings

What happens when you report someone?

  • User on a remote server: The report is sent to their instance's moderators via ActivityPub. We have no control over how it's handled.
  • User on this relay: The report arrives in our moderation panel. Our moderators can investigate, issue a warning, remove content, or ban the account (temporarily or permanently). They can also block an entire domain if necessary.

build Limitations & Troubleshooting

What are the content limits?
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Holos is more permissive than most Fediverse instances:

  • Text: No character limit (Mastodon limits to 500)
  • Media: No strict limit (a warning appears beyond 4 for compatibility)
  • Polls: No option limit (warning beyond 4)
  • Polls with media: Supported (not supported on Mastodon)
  • File size: No strict limit. Media under 10 MB are cached by the relay. Larger files are served directly from your device.

Compatibility warnings inform you that some content may not display correctly on other instances, but you can ignore them.

Can I use the same account on multiple devices?
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Yes. Holos supports multi-device: you can connect several phones, tablets, or desktops to the same account. All devices receive the same activities and stay in sync.

Adding a new device:

  • QR code transfer: The new device displays a QR code, scan it from your existing device to securely transfer your keys, followers, and posts (end-to-end encrypted via X25519 + AES-256-GCM).
  • Recovery restore: Enter your recovery passphrase to restore your identity from the encrypted backup stored on the relay.

All outgoing actions are routed through the relay proxy to keep devices in sync and prevent duplicate actions across the fediverse.

Why don't some followers see my posts?
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ActivityPub works by distribution (push), not by fetching (pull). When you post, your app sends the post directly to each follower's inbox listed locally.

Possible causes if a follower is missing:

  • You reinstalled the app without restoring your data
  • The "Follow" activity was lost or improperly processed

Solution: Ask the person to unfollow and re-follow you.

How do I report a bug or suggest an improvement?
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Go to https://codeberg.org/tom79/Holos-App/issues. First check if the issue has already been reported. If not, create a ticket with a clear title, steps to reproduce the bug, expected vs observed behavior, and your device information (model, Android/iOS version).
How can I contribute to translations?
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Translations are managed via Weblate: https://weblate.holos.social/projects/holos-app/. Create a free account and submit translations in your language. Do not edit translation files directly in the code, Weblate changes are automatically synced with the repository.

security Security & Backup

Is my data secure?
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Your private keys never leave your device. All outgoing activities are cryptographically signed, so nobody can post on your behalf.

The relay stores your public profile, cached posts, and a temporary queue of incoming activities (until your device picks them up). DMs between Holos users are end-to-end encrypted (Signal Protocol) so the relay cannot read them. However, DMs from non-Holos users are standard ActivityPub direct messages and are readable by the relay while queued.

For maximum privacy, enable E2EE, use the app regularly so queued messages are picked up quickly, and use short retention TTLs.

Are my direct messages encrypted?
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Yes, when both parties use Holos. Direct messages are end-to-end encrypted using the Signal Protocol (the same used by Signal and WhatsApp). Messages are encrypted on your device before being sent; the relay only sees opaque ciphertext.

You can verify your contact's identity via Safety Numbers in the conversation menu. If the other person uses a different fediverse app that doesn't support the Signal Protocol, messages are sent as standard (unencrypted) DMs and Holos warns you before sending.

How do backups work?
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Holos offers several layers of backup:

  • Recovery backup: After defining a passphrase, your identity (including your RSA private key), followers, and following list are encrypted locally (PBKDF2 + AES-256-GCM) then stored on the relay. Posts are saved as incremental deltas. The relay cannot decrypt any of it (zero-knowledge). This lets you restore your account on a new device.
  • Cloud backup: Configure S3-compatible or WebDAV/Nextcloud storage for full database backups (also encrypted). Schedule automatic daily, weekly, or monthly backups.
  • Local backup: Manually export your database to your device.
What happens if the relay shuts down?
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Your data is safe: everything is stored on your device, not on the relay. If a relay shuts down, you lose your @user@relay.domain address, but not your data.

With a custom domain: Simply point your DNS to another relay. Your identity and followers are preserved automatically.

Without a custom domain: Use the standard ActivityPub Move protocol to redirect your followers to a new account on another relay (or any fediverse instance). Your posts and keys remain on your device.

This is why custom domains are recommended: they make you completely independent from any single relay.

What happens if I lose my phone?
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If you have another device connected to your account, you can use QR code transfer to set up a replacement device instantly.

If the lost phone was your only device, enter your recovery passphrase on the new device to restore your identity, followers, and posts from the encrypted backup on the relay.

If you also have a cloud backup (S3 or WebDAV), you can restore your full database including message history.

Without any recovery or backup configured, you will need to create a new account.

What does the relay actually see?
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Transparency matters. Here's exactly what the relay can access:

  • Your public profile and posts (cached for availability)
  • Incoming activities in queue: until your device picks them up, including non-E2EE DMs (readable while queued)
  • Metadata: who follows you, who you follow, timestamps, activity sizes
  • Your IP address (for session management and anti-abuse)

What the relay cannot see:

  • Your private keys (never leave your device)
  • E2EE messages between Holos users (opaque ciphertext)
  • Your recovery backup content (encrypted with your passphrase, zero-knowledge)
  • Your local database (posts drafts, message history, filters, etc.)

The relay masks your IP from other fediverse instances by proxying all federation traffic.

Can I delete my account and export my data?
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Export: You can export your data at any time from the app settings. The export includes your posts, bookmarks, lists, filters, and followed hashtags in a portable JSON format. You can also do a full database backup (local file, S3, or WebDAV).

Deletion: You can permanently delete your account from the app. This sends a Delete notification to all your followers (ActivityPub standard), removes all your data from the relay (profile, cache, pending activities), and clears your local database. This action is irreversible.

arrow_circle_right Going Further

Can I migrate to or from another instance?
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Yes. Holos supports the ActivityPub migration protocol (Move). You can import your subscriptions from another instance, and if you leave Holos, you can redirect your followers to your new account.

Migration between relays with your own domain: If you use your own domain via CNAME, you can change relays without performing an ActivityPub migration. Simply register your account on another relay and redirect your CNAME to that new relay. This option requires technical skills (DNS management).

Why isn't Holos on the App Store or Play Store?
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Holos is currently available on F-Droid (Android), AltStore (iOS), and TestFlight (iOS beta). The App Store and Play Store releases are planned once the project reaches full stability. In the meantime, direct APK and IPA downloads are also available on the download page.
Can I self-host my own relay?
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Yes. The relay server is open source (AGPL-3.0) and designed to be self-hostable. You need Node.js, PostgreSQL, and Redis. See the source code and documentation on Codeberg.
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