Why Fyber
Five reasons to borrow or deposit here, each one a mechanism you can verify on-chain rather than a promise.
Every claim on this page is a mechanism, not an intention. Each one names the rule that makes it true.
1. You set the rate, and nobody can raise it
On a pooled lending market your borrowing cost is a utilisation curve. Somebody else's deposit or withdrawal reprices your loan, at any hour, without asking you. On Fyber your rate is a number you write into your position when you open it, anywhere between the tier floor and 100%.
The only thing your rate controls, besides your cost, is your position in the redemption queue: cheaper borrowers are redeemed first. That is the whole trade-off, and it is yours to make.
Guarantee
No contract function exists that can change your rate. Only you, or a delegate you have explicitly
authorised within bounds you set, can call setRate on your position.
Rules R-5.7.1, R-5.8.1
The floor moves with the market rather than with anyone's opinion: it is the larger of a fixed value — 1.5% for Tier 1, 3.0% for Tier 2 — and a multiple of a USDG borrow rate read on-chain from a reference Morpho market, clamped to the 2–6% band. If the reference goes missing, the floor falls back to the fixed value. Nobody posts it.
Rule R-5.7.2
2. Depositors are paid by borrowers, and the arithmetic is published
The Stability Pool receives 90% of every interest payment, every origination fee, every rate-change fee and every PSM fee, minted directly to it as it accrues. Every unit of it was paid by a borrower who chose the rate they pay, and the split that routes it is fixed in the constructor.
How it is calculated
current yield = 0.90 × weighted average borrower rate × total debt ÷ pool size
example: $9.1M debt × 5.0% × 0.90 ÷ $5.05M pool = 8.1%
That number is a ratio, not a level. It does not fall when the protocol grows and it does not collapse when a large depositor leaves — the pool and the debt move together. Alongside it the interface shows a realised 30-day figure computed from the share price of sfyUSD, which is history rather than projection. Both are displayed with their formula and both are labelled as computed, never as offered.
Rules R-9.4.1, R-10.2, R-10.7
3. It runs 24 hours a day, and out-of-session prices are treated as less certain
The underlying stocks trade on a schedule. Your loan does not. Borrowing, repaying, depositing, withdrawing, redeeming and swapping are available at all hours.
What changes outside the regular session is how much confidence the protocol places in the price. Out-of-session valuations are deliberately conservative, they slide back to the normal rules automatically when the official print resumes, and a downward move must be confirmed by two independent sources before it can trigger anything. See Markets never close.
4. Nothing can be changed after deployment
There is no owner, no role, no proxy, no timelock, no setter, no migration function and no selfdestruct on any of the nineteen modules. Every parameter is either fixed in the constructor, computed on-chain from a formula, or a dated step in a table written before launch. The absence is verifiable: you can check the deployed bytecode for the missing functions.
One key exists. It is a 2-of-3 Safe held by the development company, it can only freeze (for at most 72 hours at a time, 30 days cumulative per branch over its whole life) or close (irreversibly), it can never touch repayment, withdrawal, collateral claims or the PSM exit, and it stops working 365 days after deployment. Its address, its consumed budget and its countdown are on a public page.
Rules R-12.1.2, R-12.1.5, R-12.1.7, R-12.2.1
5. There is always a door out
Three of them, and none can be closed by anyone:
- Repay in fyUSD, or in USDG through
repayWithUSDG, at any hour and in any protocol state. - Swap fyUSD for USDG at the PSM for a 0.20% fee, as long as the reserve holds — never pausable, not even by the Closer.
- Redeem fyUSD against collateral at oracle price during market hours, which is what holds the floor under the price.
Guarantee
PSM.swapOut, SP.withdraw, claimCollateral, claimSurplus, close and sfyUSD.redeem are
blocked in no state, by no role, including the Closer.
Rule R-4.4.1
The honest comparison
A private bank's lombard loan gives you 50–70% loan-to-value against a securities portfolio, after a two-week file and usually above a six-figure ticket. A US broker's margin account gives you similar terms if you are a US resident. Fyber gives you 80% against tier 1 collateral, in one transaction, with published rules, wherever you are outside the restricted jurisdictions.
What it does not give you is leverage. If you want 10× on an index, a perpetual future is a better instrument and this documentation will not pretend otherwise.
Risk
Fyber is new code holding securities-backed tokens issued by a company incorporated in October 2025, on a chain whose sequencer is operated by a single party. The mechanisms above are real; they do not make the exposure small. Risk summary.
Last reviewed: 2026-09-07 · Spec v0.4
Introduction
Fyber in one page — borrow dollars against tokenized US stock exposure, at a rate you set yourself, on contracts that nobody can change.
What Fyber is, and what it is not
Which category of financial product this is — an immutable CDP, not a bank deposit, not e-money, not a broker, not a margin account — and what follows from that.