What it does, and what it costs
Tidemarks is an epub reader that runs in a browser. Importing, reading, highlighting, note-taking, typesetting and exporting all happen on your own device — a book you open is never uploaded, and neither are your notes or your place in it.
An account exists for one reason: to carry those things between your devices, and to let an AI agent read them through Tidemarks' MCP server. That half runs on a server, so that half is what is paid for.
Reading — always free
No account, no charge
Import, read, highlight, take notes, change the typesetting and export what you have marked. All of it in your browser, all of it on your device. Nothing here expires and nothing here asks for an email address.
Free account
No charge
Three books sync between your devices, and a connected agent can read those three. Every other book stays where it is, on the device you imported it to.
Paid
US$20 a year
Every book syncs, with no limit on how many, and a connected agent can read all of them. Billed once a year; there is no monthly plan and no per-device charge. The price shown at checkout is what applies, and Paddle adds any sales tax, VAT or GST due where you live.
The subscription renews each year until you cancel it. You can cancel at any time from Paddle's customer portal, and within 14 days of paying you can have the payment back — see therefund policy.
If you stop paying, the server's copy of your books is kept for 24 months, and the books, notes and positions on your own devices are untouched.
Would rather not pay?
All of Tidemarks is open source, under the MIT licence — the reader, the renderer and the syncing server alike. The only part you would have to run is the server: the reader is already running in your browser, so there is nothing else to host.
The source and the deployment guide are public.
Who you are buying from
Tidemarks is supplied by Sad Coder, Inc., 5F., No. 50, Zhongyang 7th St., Xindian Dist., New Taipei City 231014, Taiwan. Payments are handled by Paddle as merchant of record; see the terms of service. Questions: contact@tidemarks.io.