Sync relay guide

Updated July 15, 2026 · Simply Finance

Run sync on your own terms.

Simply Finance already includes a built-in sync relay, so most people never need to touch this. This page is for anyone who wants the relay to run in an account they control.

  • ✓Local-first by default
  • ✓End-to-end encrypted sync
  • ✓Bring your own sync relay when needed
What relays seeEncrypted blobs only

Relays move data between devices, but they do not get readable transaction data.

Best fitPeople who want control

The browser setup is guided; no server administration is required.

Want the protocol-level details?

Simply Finance syncs over SimplySync, our local-first sync engine. The SimplySync developer guide has the deployment and relay implementation references.

What a sync relay does

A sync relay is the small network service that helps your devices exchange encrypted changes. Think of it as a mailbox for sync updates, not as a database operator reading your finances.

Simply Finance stays local-first. Your device keeps the working copy of the database. The relay only helps devices discover and exchange encrypted updates so the same owner can restore and sync across your iPhone and Android devices.

  • Your data is encrypted before it leaves the device.
  • Relays cannot read balances, transactions, budgets, or notes.
  • Adding a custom relay changes the transport path, not the ownership model.

Who should use this

Most users should keep the built-in setup. It is the managed default for ongoing sync, and it keeps restore working out of the box.

Bring your own relay when you want tighter infrastructure control: self-hosting, a provider you trust, a regional endpoint, or a second relay for resilience.

Good rule of thumb

If you do not already know why you want a custom relay, you probably do not need one yet.

Built-in relay availability

We plan to keep the built-in relay available for as long as capacity allows. If demand grows beyond what we can sustainably provide, it may be retired later. Your own relay gives you an independent sync path.

How it works in Simply Finance

Open Settings > Sync Relays to inspect current relays, check their status, or add a new one. When you add a compatible relay URL, Simply Finance starts using it for the same encrypted owner data.

  • The built-in relay remains enabled by default for normal, ongoing sync. It is not only a testing relay.
  • You can verify a relay is healthy from the Connected status badge.
  • You can remove custom relays later without affecting local data already on the device.
Important

The recommended Cloudflare setup is browser-based and does not require server administration. Docker and VPS hosting remain available for technical users.

Host your own relay

The easiest path runs the relay in your own Cloudflare account. Cloudflare creates the storage and gives you a public HTTPS URL; no server, domain, or networking setup is required.

Recommended: deploy in your browser

Using ChatGPT or Claude Code?

Open the SimplySync Relay repository and tell the agent: “Host my own SimplySync relay.”The agent handles tooling, Cloudflare setup, deployment, and verification. You only take over for login, MFA, CAPTCHA, billing details, or terms.

Your relay URL does not need to be secret. The relay only stores ciphertext, and each owner is protected by a private write capability derived from the recovery phrase.

Deploy to Cloudflare
Step 1

Sign in

Sign in to Cloudflare and connect GitHub or GitLab if prompted.

Step 2

Deploy

Keep the suggested names. Cloudflare creates the Worker, D1 database, and R2 bucket automatically.

Step 3

Copy the URL

Copy the HTTPS address ending in workers.dev after deployment.

Step 4

Add it to the app

Open Settings → Sync Relays and paste the address.

The beginner walkthrough shows each screen and the final connection check.

Advanced: Docker on your own server

If you already manage a VPS or server, the repository includes a Docker starter. This path requires a public HTTPS domain.

git clone https://github.com/simply-hq/simplysync.git
cd simplysync
./scripts/self-host-relay.sh
Technical setup only

Put Caddy and a domain in front of the Docker relay, then follow the full repository guide for backups and production operations.

Connect and test

Keep the built-in relay enabled while the custom relay goes through a real two-device sync and restore check.

Step 1

Copy the relay URL

Use the workers.dev URL printed by Cloudflare, or the HTTPS domain in front of an advanced Docker relay.

Step 2

Add it in Sync Relays

Open Settings → Sync Relays and paste the URL. Keep the mode on Built-in + custom while you verify it.

Step 3

Confirm the connection badge

Wait for the status to switch to Connected. If it fails, double-check the URL, TLS, and relay logs.

Step 4

Test restore on another device

Before you rely on the new relay, verify another device can restore and sync the same encrypted owner data.

After verification, you can keep both relays for redundancy or choose Custom only. Adding your own relay does not require giving up the built-in relay.

FAQ

Can the sync relay read my financial data?

No. The sync relay transports encrypted sync data, but it does not have the keys needed to read your transactions.

Do I need a custom sync relay to use sync?

No. The built-in relay is the managed default and is intended for ongoing use. We plan to keep it available for as long as capacity allows, though it may be retired later if demand grows beyond what we can sustainably provide.

What happens if my custom sync relay goes down?

Your local database stays intact. Sync pauses until a healthy relay is available again.

Where do I learn the relay implementation details?

Simply Finance syncs over SimplySync, our local-first sync engine. The SimplySync developer guide is the right source for hosting, protocol expectations, and deeper implementation notes.