Muster

Privacy Policy

Version 2026-10-13

the operator of Muster runs Muster and is the data controller for your personal data under UK data protection law (the UK GDPR and the Data Protection Act 2018). Contact: safety@musterchat.com.

The short version

Your messages and files are end-to-end encrypted. We can't read them.
We can see account details and the "envelope" around messages: who is in which conversation, when messages were sent and how big files are.
When someone reports a message to us, we get a readable copy of what they reported.
We don't sell your data, show ads, or use your data to train AI.

What we collect and why

Data	Why	Lawful basis
Username, display name, email address, password (stored only as a salted hash), date of birth	To run your account, confirm your email, sign you in, keep under-16s off Muster and protect 16–17 year olds	Contract; legal obligation (Online Safety Act)
Profile picture, about me, banner colour, status	To show your profile to others	Contract
Encrypted messages and files	To deliver them. We hold them only in scrambled form and can't read them	Contract
Message metadata: which conversations and servers you're in, when messages were sent and edited, file sizes, reactions, poll votes, replies, server roles, blocks and notes	Needed to run chat, servers and moderation	Contract; legitimate interests (keeping Muster safe)
Encryption public keys for your devices	So others can encrypt messages to you	Contract
IP addresses and times when you sign up, log in or open Muster	Security, stopping abuse, and because the National Crime Agency asks for them in child-safety reports	Legitimate interests; legal obligation
Reports you send, and reports about you, including the reported messages and files	To deal with illegal and harmful content and meet our Online Safety Act duties	Legal obligation; legitimate interests
Moderation records (what we did and why)	Accountability, appeals and our legal duties	Legal obligation; legitimate interests

Voice and video calls go directly between devices, encrypted. We don't record or store them.

Cookies and storage on your device

We use one cookie: a session cookie that keeps you signed in. It's strictly necessary, so we don't ask for consent. Muster also keeps small settings in your browser (for example, your recently used emoji, and the encryption key for that browser, which never leaves it). No advertising or tracking cookies.

Who we share data with

Hosting: Render (servers in Frankfurt, Germany) stores Muster's data for us.
Email: our email provider sends verification codes and safety alerts.
Google: only if you choose "Continue with Google", to confirm your email address.
Password check: when you choose a password, we check it against known breached passwords using Have I Been Pwned's range search, which only ever sees the first 5 characters of a hash of it.
GIFs and YouTube: GIF searches go through our server, but the GIF images load from KLIPY, and a YouTube video loads from YouTube (privacy-enhanced mode) only when you press play. Those services see your IP address when that happens.
Calls: to connect calls, your device contacts a Google "STUN" server, which sees your IP address. The other people in a call can also see it, as with any direct connection.
Authorities: we report child sexual exploitation and abuse content to the National Crime Agency as UK law requires, and may share information with the police or other authorities where the law requires or allows it (for example, to protect someone's life).

Render stores data in the EU, which the UK recognises as giving adequate protection. If any provider moves data elsewhere, we rely on the UK's approved safeguards.

How long we keep things

Data	How long
Your account and messages	Until you or we delete them
Sign-in IP addresses	90 days
Reports and the content in them (closed reports)	1 year after the report is closed
Reports referred to the National Crime Agency	Content and related data for 1 year after the referral; the NCA's reference number for 5 years (both required by the Online Safety (CSEA Content Reporting) Regulations 2026)
Backups	Rolling copies, overwritten within a few days

Your rights

You can ask us for a copy of your data, to correct it, to delete it, to restrict or object to how we use it, or to move it elsewhere. Email safety@musterchat.com. We'll reply within one month. Some data we must keep for legal reasons (for example, in an open child-safety referral). You can also complain to the Information Commissioner's Office at ico.org.uk.

Children

Muster is for people aged 16 and over. We ask for a date of birth at sign-up. 16 and 17 year olds can only get new direct messages from adults they share a server with. If we learn that someone under 16 has an account, we close it.

Changes

We'll update this page when things change, and ask you to accept important changes in the app.