The Asset variant of B20 — designed for assets of all kinds. Everything in B20/README.md applies; this page covers the deltas only. See IB20Asset for the full Solidity interface.
Each account's stored balance is the raw balance. A uniform on-chain multiplier scales that raw balance into a derived scaled view that consumers display. The multiplier applies to all accounts equally, which lets issuers rebase every balance at once — without rewriting individual balances — the shape is similar to wstETH wrapping stETH, where the stored unit is the unwrapped quantity and the derived unit is the rebased view.
Read the current multiplier with multiplier(); the value is in WAD precision (1e18, exposed as WAD_PRECISION()). toScaledBalance(rawBalance) converts a raw amount to its scaled view, toRawBalance(scaledBalance) is the reverse converter (integer-floored, so the round-trip can lose up to one ULP), and scaledBalanceOf(account) is a convenience over ERC-20's balanceOf that returns the same account's raw balance in its scaled form.
updateMultiplier(newMultiplier) updates the multiplier and should be wrapped in an announcement (see Announcements).
Announcements are publicly viewable notifications posted by a token operator. They can represent anything the operator wants to create a record of and can be coupled with actual state changes on the token (updating the multiplier, batched mints, and so on).
An announcement is delimited by a paired Announcement(msg.sender, id, description, uri) event (opens the bracket) and EndAnnouncement(id) event (closes it). Every state-changing call dispatched inside the bracket belongs to that announcement. A recursion guard prevents nesting, and each id is enforced unique forever (AnnouncementIdAlreadyUsed) so indexers can correlate brackets across transactions.
Indexers should treat every Announcement log as the start of exactly one bracket; effects between Announcement and EndAnnouncement belong to the announced action; effects emitted without a surrounding bracket are direct invocations and should be flagged as emergency overrides.
Wrap a set of operations in a single announcement by calling announce(internalCalls, id, description, uri). The function (gated by OPERATOR_ROLE) emits Announcement, dispatches each internal call via self-delegatecall (which preserves msg.sender so the inner role checks see the operator), then emits EndAnnouncement. Inner reverts are wrapped in InternalCallFailed rather than bubbled — replay the call directly to debug. Nested calls to announce revert with AnnouncementInProgress; calls shorter than 4 bytes revert with InternalCallMalformed.
// Disclose and apply a community-ratified rebase atomically.
bytes[] memory internalCalls = new bytes[](1);
internalCalls[0] = abi.encodeCall(IB20Asset.updateMultiplier, (newMultiplier));
IB20Asset(token).announce({
internalCalls: internalCalls,
id: "2026-Q3-rebase",
description: "Community governance proposal #42: ratified rebase",
uri: "https://disclosures.example.com/..."
});batchMint(recipients, amounts) mints to many accounts in one call, gated by MINT_ROLE. It should be wrapped in announce(), which additionally requires the operator to hold OPERATOR_ROLE (typically granted as a single bundle).
Each Asset token can carry an arbitrary set of named metadata entries — a general-purpose key/value store the issuer is free to use however they want (e.g. "category" → "electronics", "region" → "north-america", "reference" → "REF-2024-001"). Read with extraMetadata(key); the value is a string. All entries are optional and added post-creation — the factory does not seed any entry at token creation.
updateExtraMetadata(key, value) adds, updates, or removes an entry, gated by METADATA_ROLE (the same role that gates updateName / updateSymbol). It does NOT require OPERATOR_ROLE and can be invoked directly without an announce() wrapper. Passing an empty value removes the entry. An empty key reverts with InvalidMetadataKey.
Gates the updateMultiplier and the announce. These are metadata-like operations — they post disclosures and rescale the displayed balance rather than moving raw balances directly — but a compromised operator carries materially higher severity than ordinary metadata edits, so the capability is elevated into its own independent role instead of being folded into METADATA_ROLE. Held separately from DEFAULT_ADMIN_ROLE so operators don't need full admin authority.
decimals() is chosen at creation via B20AssetCreateParams.decimals and immutable thereafter. The factory enforces the inclusive range [6, 18] (exposed as B20Constants.MIN_ASSET_DECIMALS and MAX_ASSET_DECIMALS); out-of-range values revert InvalidDecimals(decimals). 6 is the smallest unit any asset should use and 18 is a reasonable ceiling that encompasses the supermajority of assets.