What Is a Stablecoin? The Classes, the Exemplars, the Map

The definition, unpacked

A stablecoin is built to hold a steady value against a target. The target is most often one US dollar. The token itself is an ordinary blockchain asset. The machinery behind the token is what makes it a stablecoin. A reserve. A collateral pool. Or a rule set meant to pull the price back when it drifts.

The machinery is the classification. This site sorts tokens by what stands behind them. The backing decides what documents exist. It decides what can be verified. It decides how the design fails.

The four classes

The fiat-backed class holds conventional money assets. Tokens issue against them. USDT and USDC are the majors. Both carry recurring third-party reports on their reserves. The class page fiat-backed stablecoins walks the mechanics and the documents.

The crypto-backed class locks cryptocurrency as collateral. The collateral is worth more than the debt it backs. The verified exemplars are the Sky dollar, DAI’s successor, plus LUSD and BOLD from Liquity’s designs ^[2]. The class page crypto-backed stablecoins makes the overcollateral rule explicit.

The gold-backed class ties each token to a quantity of metal. PAXG assigns one fine troy ounce of allocated vault gold per token ^[3]. Tether Gold states its holdings on its issuer site. The gold-backed page carries both. It also carries the wider commodity class.

The algorithmic class held its peg by rules alone. Supply expanded. Supply contracted. No reserve stood anywhere. The class is history now. The canonical case, Terra’s UST, collapsed in May 2022. Its price ended near one cent ^[4]. The algorithmic page tells that story. It also carries the corrections the collapse forced.

The exemplar list, corrected

Older copy names Tether, USDC, DAI, and BUSD as the popular exemplars. Three of four stand. BUSD does not. Paxos states it on its own page. It no longer mints new BUSD. Customers can still redeem for dollars or convert to USDP ^[1]. A list carrying a dead-minted token is a list that has not been re-read.

The current set on this site: USDT and USDC as the fiat majors. The Sky dollar as the crypto-backed flagship. PAXG and Tether Gold as the gold pair. Each has a token page with figures and sources. Each figure carries its date.

One more name belongs on the corrected list. The old copy filed DAI under the popular set without noting what it is. DAI is the crypto-backed class’s original token, launched in 2017, and it still runs today beside its successor. The rename story, and the supply lessons that came with it, live on the Sky dollar’s token page.

What is not in the taxonomy

Government digital currency is not a fifth class here. A central bank digital currency is state money in token form. That is a different asset class, with its own pages. Older copy carried a country-backed stablecoin type. The correction is structural. A state issuer moves the instrument out of this taxonomy entirely. The distinction is not pedantry. A stablecoin is a liability of an issuer. You can read the issuer’s documents. A central bank instrument is the currency itself. Different questions attach.

Bitcoin is not in the taxonomy either. It targets nothing. Its value floats against everything, by design. The two share transfer rails and nothing else. That is why this site keeps them in separate trees.

How the peg is defended

Every class answers one engineering question. What pulls the price back when it drifts? The fiat answer is redemption. Arbitrage against the issuer’s dollar path does the work. The crypto-backed answer is collateral plus liquidation. Excess locked value absorbs the moves. The commodity answer is the fiat answer with metal in the reserve. The algorithmic answer was supply rules. That answer’s record is the section above.

One failure shape recurs. The secondary-market price is a market fact. It can leave the peg for hours or days, whatever the design. The documented cases live in this library’s depeg records. Feeds and pairs are named in each. The risks page turns them into the history check.

How this site covers the classes

The series runs four pages deep from here. One per class. Each class page links the token pages behind its exemplars. The token pages carry the figures. Supplies. Reserve compositions. Report dates. Auditor signatures. Each with its source and its date. The figures move. The pages move with them. The reviewed date at the foot says when it last happened.

Nothing on those pages ranks one token against another. The method is simpler and stranger. Say what a document says. Name the document. Date the read. Let the reader decide.

Where the map leads

Every class page above links back here and down to its token pages. The stablecoins hub is the pillar root, with USDT and USDC carrying the two majors figure by figure, and the cryptocurrency hub is this page’s home root. When any page here names a number, the number has a source and a date. That is the habit the whole library runs on.