The public chain
Sees
- Two shielded transactions, shaped like 86.5% of Ironwood traffic
Never sees
- Amounts, sender, receiver
- That a tab existed, or that 400 payments happened
Pay-per-use on Zcash · shielded · off-chain
Pay for exactly what you use.
Nobody holds your money.
Open a tab with one private payment. Your browser, your agent or your app then pays by the second or by the request, off-chain and instantly, in amounts smaller than Zcash's own fee. When you're done, one transaction pays the service and sends the rest back to you.
Live on Zcash mainnet. Every recorded transaction can be checked from this page.
Example tab · streamingTESTNET
0payments
- Paid so far
- 0 zat
- Network fees
- 0 zat
- On chain
- 1 transaction
1 zat every 6 seconds of VPN · 1,000 zat per answer · any price per API call
How a tab works
Two transactions, any number of payments.
- 1OpenYour device and the service make a joint key neither can spend alone. The service also seals its half to a future time, your refund time, and your device checks that seal before you pay.
- 2UseEvery payment is a signed running total: a note that lets the service take this much. It costs milliseconds and nothing goes on chain.
- 3CloseOne transaction pays the service what you used and returns the rest. If the service vanishes, the seal opens at the refund time and you take everything back alone.
Who sees what
One tab, seen from every side.
The same tab of 400 payments, from the point of view of everyone who touches it. Nothing below is a promise: each line follows from what that party's own software receives.
The service
Sees
- This tab's payments and their times
- Your IP address, as any VPN does
Never sees
- Who you are, your wallet balance, your other addresses
- Your key, so it can't take more than you signed
The Zcash server
Sees
- Our relay asking for whole block ranges
Never sees
- Your IP address
- Which notes are yours: your device decrypts them
You
Hold
- Your half of the key and 24 backup words
- A refund you can sign alone at the refund time
Never need
- An account, an email or a card
- To trust the service with your money
Live today
One tab, anything metered.
A VPN, paid by the second
The standard WireGuard app on any phone or laptop. Keep it paid 1, 8 or 24 hours ahead and lock your phone; pause it, resume it, close it. No account, no card.
Try it on mainnet →Any API, paid per request
Point the proxy at an existing HTTP API and give paths a price. Unpaid calls get 402 Payment Required in the x402 v2 format. Live: an unmodified OpenAI-compatible model API.
AI agents with a hard budget
An agent funds its own tab once and pays APIs as it works, from the command line or as an MCP tool. The tab's size and a per-request cap are limits no prompt can raise.
Agent guide →Why a tab
A minute of VPN is worth 10 zat. One Zcash payment costs 10,000 zat in fees.
Paying per minute or per call with ordinary transactions costs more in fees than the thing itself. A tab pays the fee twice, once to open and once to close, however many payments happen in between.
Why you can trust it
Checked, attacked, and on chain.
–recorded tabs on this network, every transaction re-checkable at /check
486Mmalformed messages fuzzed across 8 decoders, 0 crashes
2−60chance a service passes the sealed-key check while cheating
0accounts, cards or custodians: unused value always comes back to you
For developers
Put a price on an API you already run.
proxyagent
# any existing HTTP API, no code change
TIDVAR_UPSTREAM=http://127.0.0.1:3000 \
TIDVAR_ROUTES='/api/search=3000,/api/*=500' \
tidvar-kit-demo
# an agent pays it from its own tab
tidvar-agent open --service https://tidvar.site --amount 0.0005 --return <your address>
tidvar-agent fetch https://…/api/search --data '{"q":"zcash"}'
tidvar-agent close # the rest returns to youPrivate Zcash · off-chain · by the second
Pay by the second.
Keep the rest.
A VPN and an AI chat you pay for in private Zcash, as you use them. Each payment is smaller than Zcash's own fee, and we never hold your money: what you don't use comes back to you.
- 1Open a tabOne shielded payment into a lock that needs your key and ours.
- 2Use itYour browser pays every 10 seconds, off-chain, exactly for what you use.
- 3Close itOne transaction. The rest comes back to you, or to you alone at the refund time.
No keys needed
Check it yourself
Every tab we recorded, re-checked now. This page fetches each transaction from the public Zcash server through our relay and recomputes its id from the raw bytes. The same check runs from a terminal with tidvar verify.
For judges
Judge access
Paste the judge code from the submission. It opens a real mainnet tab that already holds ZEC, so you need no wallet and no account. The code stays in this browser.
Step 2 of 3
Fund your tab
Download backup
Keep this encrypted file and your backup words before paying.
We haven't seen your payment yet. It shows up after one block (about a minute).
Your tab
Streaming payments
- Used
- 0 zat
- Paid
- 0 zat
- Covered until
- Waiting for the first payment
- Tab value
- Waiting for your payment
- On chain
- 1 transaction so far
VPN: 1 zat every 6 seconds, paid off-chain every 10 seconds while this page is open. Stop paying and the VPN cuts off within seconds.
The page always keeps this much VPN time paid in advance, so you can close it or lock your phone and the VPN keeps running. Time you don't use comes back to you when you close the tab.
Connect WireGuard
On this phone, download the file and import it in WireGuard with + → Import from file or archive. Scan the QR only from another device. This file holds your VPN key: keep it private.
Download WireGuard fileShow QR for another device
Top up this tab
Pay more into the same tab address from your wallet. It counts after one block and you can spend that much more, with no new tab and no new keys. A tab takes up to three top-ups; what you don't use still comes back when you close.
Renew this tab
One transaction closes this tab, pays the service what you used, and moves everything else into a new tab with a fresh refund time. No new payment from your wallet. The new tab has its own keys and its own backup words.
Save these 24 words for the new tab. Never send them to anyone or show them in a recording.
1,000 zat per answer
Tidvar Chat
Paid from this tab, about one cent an answer. The model (Qwen2.5 1.5B Instruct, Apache-2.0) runs on this service's own server; your message is not stored and history stays in this browser. A message the model can't answer is not charged.
Developer kit
Any service can charge per request from a tab with tidvar-402. This call costs 2,000 zat.
Tools
Timings stay on this device. The download holds sync and signing durations, timer gaps and close receipts; no backup words or VPN keys.