A non-collateralized stablecoin, also called an algorithmic stablecoin, is a token designed to hold a $1 peg without holding any dollars, Treasuries, or crypto in reserve. Instead of redemption against a backing asset, an algorithm expands or contracts the token supply to push price back toward $1. The best-known example, TerraUSD (UST), reached a market capitalization above $18 billion in early May 2022 before losing its peg and collapsing within a single week, per a Congressional Research Service brief.

Non-collateralized stablecoins are a narrow, high-risk slice of the broader stablecoin market. Most of what circulates today, USDT, USDC, and the rest, is fiat-backed and reserve-redeemable. This article covers the mechanism specifically: how seigniorage and rebasing models try to hold a peg with no collateral, why UST is the reference failure case regulators still cite, and what current US law says about the category. Some 2026 roundups use "algorithmic stablecoin" more broadly to include collateralized designs like DAI, crvUSD, and Ethena's USDe; see Top Algorithmic Stablecoins 2026 for that current-usage view. This piece covers the original, strictly non-collateralized meaning.

A non-collateralized stablecoin is a digital asset that targets a stable price, usually $1, using an algorithm or smart contract rather than a held reserve of fiat currency or crypto collateral. Supply expands when the price trades above the peg and contracts when it trades below, with the expectation that the resulting arbitrage restores parity. No custodian holds redeemable assets behind the token.

The Congressional Research Service describes the category plainly: algorithmic stablecoins "generally do not attempt to achieve value by holding a reserve of fiat-denominated assets," relying instead on minting, burning, rebasing, or arbitrage mechanisms to manage supply. That is the dividing line from fiat-backed stablecoins like USDC and USDT, which redeem 1:1 against dollars or Treasuries held by the issuer, and from crypto-collateralized designs that lock volatile assets in vaults. Non-collateralized models hold nothing; the peg is a promise enforced by code and market incentives, not a claim on an asset.

Non-collateralized stablecoins hold a peg through two main mechanisms: seigniorage (dual-token) models, which mint or burn a second, volatile token to absorb supply changes, and rebasing models, which directly adjust the number of tokens in every wallet. Both rely on the assumption that rational arbitrage will restore $1 parity, an assumption that has repeatedly failed under stress.

In a seigniorage design, described in detail by Kraken's algorithmic stablecoin explainer, the system uses two tokens: the stablecoin and a companion "bond" or balancer token. If the stablecoin trades above $1, the protocol mints new units and distributes them to holders of the companion token, and supply growth is meant to push price back down. If the stablecoin trades below $1, the protocol sells discounted bond tokens redeemable for $1 later, absorbing stablecoins out of circulation to shrink supply. UST used exactly this structure with its companion token, LUNA: anyone could burn $1 of LUNA to mint 1 UST, or burn 1 UST to mint $1 of LUNA, and the arbitrage was supposed to hold the peg in both directions.

Rebasing stablecoins skip the second token entirely. Ampleforth (AMPL) is the clearest example: when AMPL trades above $1, every wallet's balance increases proportionally; when it trades below $1, every balance shrinks. Holders keep the same share of total supply, but the number of tokens in their wallet changes daily based on price. The peg mechanisms and reserves overview compares this approach against reserve-backed and crypto-collateralized alternatives across the wider stablecoin market.

Both mechanisms depend on a rational arbitrageur showing up at exactly the moment the peg drifts, and depend on that arbitrageur believing the trade will actually close at a profit. That belief is the load-bearing part of the system. In calm markets, small deviations from $1 get closed quickly because the trade is low-risk and repeatable. Under stress, the same arbitrage trade carries execution risk: an arbitrageur burning UST for LUNA during a selloff is left holding a rapidly depreciating asset if LUNA's price keeps falling before they can sell it, which is exactly the dynamic that broke down in May 2022. Once arbitrageurs stop showing up, the mechanism that is supposed to defend the peg has nothing left to do the defending.

The category splits into three recognized designs: pure seigniorage (dual-token) stablecoins, single-token rebasing stablecoins, and fractional-algorithmic hybrids that combine partial collateral with an algorithmic supply mechanism. Only the first two are "pure" non-collateralized designs; the third holds some backing and is usually classified separately once it adds real collateral.

UST/LUNA is the largest example by far, but it was not the only one. Basis Cash and Empty Set Dollar (ESD) both launched with a nearly identical dual-token, mint-and-burn structure in 2020 and 2021. Neither ever regained its peg after breaking it; both now trade at a small fraction of their original target value, according to Changelly's algorithmic stablecoin overview. Iron Finance's IRON token used a related, partially collateralized seigniorage design paired with a volatile token called TITAN; when TITAN's price collapsed in June 2021, IRON traded more than a quarter below its $1 peg within a single day, per the same Congressional Research Service brief cited above.

Basis Cash's design borrowed directly from an earlier proposal called Basis (formerly Basecoin), which planned a three-token system of a stablecoin, bonds, and shares before its founders shut the project down in December 2018 and returned investor funds, citing SEC regulatory constraints, per Investopedia's account of the shutdown. Basis Cash revived the model on Ethereum without a central issuer in 2020, but the same core weakness applied: bond tokens are only worth buying if holders expect the peg to recover, and once a large enough share of the market stops expecting recovery, nobody buys the bonds and the contraction mechanism simply stops working. ESD attempted a variant using "coupons" instead of bonds, with an expiration window that added urgency to redemption, but the underlying reflexivity problem was the same.

Ampleforth remains the most cited rebasing design still active. Because balances adjust rather than price, rebasing tokens avoid the liquidation cascades seen in collateralized systems, but they introduce their own complexity for anyone integrating the token into a wallet, exchange, or accounting system, since a static balance is not actually static.

Frax launched in 2020 as a fractional-algorithmic stablecoin, partly backed by USDC and partly stabilized by its FXS governance token, with the collateral ratio adjusting based on demand. After UST's collapse, the Frax community moved the protocol toward full collateralization, effectively exiting the pure algorithmic category. Eco's algorithmic stablecoins comparison covers this newer generation of collateralized-adjacent designs (DAI, Frax v2, crvUSD, USDe), which is a distinct and more conservative category from the non-collateralized models this article covers.

This distinction matters for search intent as much as for risk. Most content ranking for general "algorithmic stablecoin" queries today, including Eco's own comparison piece, actually describes the post-UST survivors: over-collateralized CDP systems, hybrid AMO designs, and delta-neutral synthetic dollars. None of those hold the $1 peg without backing of some kind. True non-collateralized stablecoins, the seigniorage and rebasing designs covered in this article, are a narrower and considerably riskier subset that the broader "algorithmic stablecoin" label tends to obscure.

Non-collateralized stablecoins are pitched on two advantages: decentralization, since there is no custodian holding fiat reserves that can freeze funds or fail an audit, and scalability, since supply can expand instantly without waiting on a bank to receive new deposits. In practice, both advantages have proven difficult to realize without the peg breaking under stress.

On decentralization, fiat-backed stablecoins carry counterparty risk: holders trust that Circle or Tether actually holds the reserves it discloses, and that trust could fail if reserves turn out to be misstated or if a regulator freezes issuer assets. A non-collateralized design is fully onchain and auditable by anyone reading the smart contract, per Kraken's explainer, which removes that specific counterparty risk. On scalability, because there is no reserve to fund, supply can, in theory, expand to meet demand with no external capital injection at all.

The tradeoff is that both properties come from the same design choice, no backing asset, that also removes the floor under the peg. A reserve-backed stablecoin can survive a loss-of-confidence event as long as the reserve is real and redemption keeps functioning; a non-collateralized stablecoin has nothing to point to once confidence breaks, which is why every large-scale example in this category has eventually depegged. Eco's depeg warning-signs guide covers the specific signals, like sustained trading below $0.98 or widening bond-token discounts, that tend to precede a seigniorage-model collapse.

UST is the canonical failure of non-collateralized stablecoin design. Its market capitalization exceeded $18 billion in early May 2022; within roughly a week, UST fell to a low of $0.12 and the Terra blockchain was temporarily halted, an event that erased close to $45 billion in combined UST and LUNA market value.

The mechanics were straightforward on paper. UST holders could always burn 1 UST for $1 of LUNA, and burn $1 of LUNA for 1 UST, and arbitrage was supposed to hold the $1 peg in both directions, per the Congressional Research Service brief. Two structural factors amplified the failure. First, Terraform Labs' Anchor Protocol offered a reported 20% annual yield on deposited UST, pulling in demand that had little relationship to organic payment or DeFi use. When large depositors began withdrawing from Anchor in early May 2022, it foreshadowed the depeg rather than caused it outright. Second, once UST started trading below $1, the burn-for-LUNA arbitrage meant that converting UST into LUNA flooded the market with new LUNA supply, crashing LUNA's price and destroying the very mechanism meant to defend the peg, a dynamic Wikipedia's account of the collapse describes as the breakdown of the "burn and mint equilibrium."

The Luna Foundation Guard, a reserve fund that had accumulated bitcoin to help defend UST's peg, deployed part of that bitcoin during the selloff, though observers have expressed skepticism about how effective that defense actually was. On May 25, 2022, Terra's community approved a proposal to fork the chain and abandon UST entirely, and the original chain and token now trade as Terra Classic and USTC. Eco's stablecoin depeg explainer covers the broader warning signs that apply across depeg events, not just UST's.

The scale is worth sitting with. Before the collapse, UST had been the third-largest stablecoin by market capitalization, meaning its failure was not a fringe experiment but a top-three asset in the category. The Congressional Research Service brief notes that observers raised financial stability concerns at the time specifically because of UST's contagion effects on other crypto assets and its interconnectedness with parts of the traditional financial system through investors and lenders exposed to Terra-ecosystem tokens. That contagion argument is part of why UST remains the reference case in nearly every subsequent piece of US stablecoin legislation, including the GENIUS Act's endogenously collateralized carve-out discussed below.

Non-collateralized stablecoins fail because their peg defense depends entirely on continued market confidence rather than a redeemable asset. Without a reserve to fall back on, any sustained loss of confidence triggers a "death spiral": holders sell, the defense mechanism dilutes supply further, and the sell pressure compounds instead of resolving. The result is a run-like collapse with no floor.

The Congressional Research Service brief frames this as a classic run scenario: a large number of holders exit simultaneously, triggering negative feedback loops that cascade through connected markets. Unlike a bank run, there is no deposit insurance or lender-of-last-resort backstop in these systems. UST's $18 billion collapse and Iron's single-day TITAN-driven crash both fit this pattern, just at very different scales. TRON's USDD, launched in 2022 partly in response to the post-UST vacuum, has faced its own repeated depeg episodes, which Eco's USDD depeg history covers in more detail. Every documented failure in the category shares the same structural gap: no asset anyone can redeem against when confidence breaks.

US law does not ban non-collateralized stablecoins outright, but the GENIUS Act, signed in 2025, excludes them from its "payment stablecoin" framework and the 1:1 reserve requirements that framework imposes. The Act instead directs the Treasury Secretary to study what it calls "endogenously collateralized stablecoins" and report to Congress within one year, rather than immediately regulating or banning the category.

Under the GENIUS Act, a payment stablecoin must be redeemable for a fixed amount of national currency and backed 1:1 by reserves, a definition that by design excludes tokens pegged to another digital asset's value through algorithmic means, per Morgan Lewis's summary of the Act. The competing STABLE Act proposal in the House would have imposed a two-year moratorium on endogenously collateralized stablecoins outright; the GENIUS Act took the lighter path of a mandated study instead. In practice, this means non-collateralized and seigniorage-style stablecoins currently operate outside the federal reserve, disclosure, and custody rules that apply to issuers like Circle and Tether. Eco's history of stablecoins traces how that regulatory line hardened after UST's collapse.

The gap is deliberate rather than an oversight. Lawmakers debating both the GENIUS Act and the STABLE Act were aware of UST when drafting the endogenously collateralized carve-out; the concern Morgan Lewis highlights is that an issuer could otherwise structure a stablecoin pegged to another digital asset specifically to sidestep the reserve and audit requirements that apply to true payment stablecoins. Until the Treasury's mandated study lands, roughly one year after the Act's 2025 enactment, non-collateralized stablecoin issuers face no federal reserve requirement, no mandated monthly attestation, and no first-priority claim protection in insolvency, all of which GENIUS Act-compliant issuers must provide.

The primary risk is total loss with no recourse: because there is no reserve, no redemption right, and often no custodian, a broken peg can go to near zero with nothing to recover against. Secondary risks include reflexive collapse dynamics unique to dual-token designs, thin liquidity outside a failure's early hours, and regulatory uncertainty since the category sits outside frameworks like the GENIUS Act.

Beyond the collapse risk itself, non-collateralized designs carry integration risk for anyone building on top of them. Rebasing tokens like AMPL change wallet balances on a schedule, which breaks naive accounting assumptions. Dual-token seigniorage systems create correlated exposure between the stablecoin and its companion token, so a holder in "just the stablecoin" is still exposed to the companion token's liquidity and price action during stress, exactly what happened to LUNA holders in May 2022. Eco's stablecoin issuer reserves explainer covers what reserve-backed alternatives disclose that non-collateralized designs structurally cannot.

Liquidity risk compounds these problems during a stress event. In normal conditions, seigniorage and rebasing tokens can trade close to peg on modest volume. Once a depeg starts, order books thin out fast, since market makers who would normally arbitrage the gap have no reserve asset to hedge against and typically withdraw rather than lean into a falling token. That thin-liquidity dynamic is part of why UST fell from roughly $1.00 to $0.12 within days rather than finding a stable discount, per the CRS brief cited earlier in this article.

Anyone evaluating a non-collateralized stablecoin for treasury, payments, or DeFi collateral use should start from the opposite assumption of a reserve-backed asset: rather than asking what backs the token, the right question is what mechanism is supposed to defend the peg, and what specifically happens to that mechanism when a large holder decides to exit all at once. For UST, the answer was that exiting flooded the market with LUNA. For Basis Cash and ESD, the answer was that bond buyers simply stopped showing up. Every non-collateralized design has some version of that same failure mode, because none of them have an asset sitting in reserve that can absorb the exit instead.

Eco's infrastructure is built around reserve-backed and crypto-collateralized stablecoins moving across chains, the category that dominates real payment and settlement volume today. Non-collateralized designs like UST are relevant mainly as a risk case study: they explain why most serious payment infrastructure, including the routing and reference-rate tooling Eco documents in its reference rate guide, is built around assets with an actual redeemable reserve rather than an algorithm alone.