Stablecoin Blacklisting 101

What blacklisting is

Most large stablecoins, including Tether's USDT and Circle's USDC, are not "yours" the way Bitcoin or Ether are. They're tokens issued by a company, and that company writes a privilege into the token's smart contract: the power to blacklist (freeze) any address that holds the token.

Only the issuer can do it. When an address is blacklisted, the issuer flips a flag on the contract for that address. From that moment the address can no longer send the stablecoin. The balance is still visible on-chain, it's just frozen in place.

Why this makes stablecoins different from BTC and ETH

Bitcoin and Ether are native assets. No person or company can freeze them; there is no privileged party in the protocol who can stop you from moving your coins. The only thing that controls native crypto is the private key.

Issuer-controlled stablecoins are the opposite. Because USDT and USDC are claims on a company's reserves, that company keeps a kill switch over any address holding the token. That's the core trade-off of a centralized stablecoin: you get a dollar-pegged asset backed by reserves, but the issuer can freeze individual holders at will.

Why it's used, and when

Issuers generally freeze addresses in response to outside pressure or clear abuse, including:

• Law-enforcement and court orders: a request or order to immobilize specific funds.

• Sanctions compliance: e.g. addresses tied to sanctioned entities or jurisdictions.

• Theft, hacks and fraud: freezing stolen funds to stop them being cashed out, often within minutes of an exploit.

Freezes aren't always announced, and the on-chain action can lag the underlying request - which is exactly the kind of activity this site tracks.

What a freeze actually prevents

A blacklist blocks outgoing transfers from the frozen address. The holder can no longer move the tokens out. On USDT it does not block incoming transfers: funds can still be sent to a frozen address.

A frozen USDT address is a one-way valve: nothing leaves, but money can still flow in - so a blacklisted balance can keep growing.

(USDC is slightly stricter here - see below.)

Unblacklisting

Freezes aren't necessarily permanent. The issuer can later unblacklist (thaw) an address, restoring its ability to send - for example when a freeze was applied in error, a dispute is resolved, or an investigation concludes. Unblacklistings are far less common than freezes, but they do happen, and they're recorded on-chain just like the original freeze.

USDT vs USDC: two different toolkits

Both issuers can freeze, but they diverge sharply in how they handle the frozen funds, and in how much of that is visible on-chain.

USDT (Tether): freeze and destroy on-chain

Tether's contracts include a destroyBlackFunds function. After freezing an address, Tether can permanently burn the frozen balance directly on the blockchain - the tokens are removed from circulation entirely. Each destruction is a single, visible on-chain event.

USDC (Circle): freeze on-chain, remove off-chain

Circle's USDC contract can blacklist and un-blacklist, but it has no on-chain function to destroy a specific holder's balance. Circle can't burn an individual address's USDC on-chain. Instead, removing value is handled off-chain through Circle's own reserve and redemption processes: the frozen tokens simply sit immobilized on-chain. USDC's contract is also stricter on transfers - it blocks sends to a blacklisted address as well as from one.

The practical upshot: on this site you'll see destroyed-funds events for USDT but never for USDC. That difference isn't an oversight in our data, it reflects how the two tokens are actually built.

Why we track this

Blacklisting is one of the most consequential, and least visible, powers in crypto. blocklist.fyi observes these freezes, thaws and destructions across every chain where USDT and USDC are issued, so the activity is a matter of public record rather than something you only hear about after the fact.