Sidechain · settles to Bitcoin
Stacks ticker STX
Summary
Proof of Transfer. For each Bitcoin block, miners send BTC in block-commit transactions and a verifiable random sortition, weighted by the BTC each committed, picks one miner for a tenure. Since the Nakamoto upgrade (Q4 2024) that miner proposes Stacks blocks roughly every 10 seconds, and each block needs signatures carrying at least 70% of signer weight, where weight comes from STX locked by stakers. Under PoX-5, activated 30 July 2026 at Bitcoin block 960,230, committed BTC goes into a reward pool that is converted to sBTC, instead of being paid straight to stakers' Bitcoin addresses, and none is burned. At each following Bitcoin block the Stacks state as of the start of the prior tenure is written to Bitcoin. Bitcoin does not check whether Stacks transactions are valid; Stacks nodes and signers do. 234567827
Design
- System
- SidechainStacks calls itself a Bitcoin L2, and its docs admit it does not fit neatly into existing categories. It is filed here as a sidechain because it has its own block producers (BTC-bidding miners) and its own block approvers (signers weighted by staked STX), Bitcoin cannot check Stacks transactions or force withdrawals, and BTC enters and leaves through the sBTC peg held by a signer set. It is not a rollup. Its leader election, ordering and anchoring follow Bitcoin blocks. STX is the native gas and reward token.
- Settles to
- BitcoinLeader election, tenure ordering and state anchoring use Bitcoin blocks, and a Bitcoin reorganization reorganizes Stacks. Bitcoin does not validate Stacks transactions or enforce withdrawals: BTC moves in and out through the sBTC signer set, and sBTC withdrawals wait for six Bitcoin confirmations.
- Settlement family
- Bitcoin family
- Scarce resource
- Other
- State model
- Accounts
- Finality
- Checkpointed
- Who makes blocks
- One miner per tenure, chosen by BTC-weighted sortition; the mining docs say Stacks has at least 4-5 miners with open membership. Signers approve every block; a signer-manager needs 50,000 STX staked to it in aggregate to join the signer set.
- Fork choice
- Tenures follow Bitcoin's canonical chain: after a Bitcoin reorganization, signers restart from the last shared sortition and dropped Stacks transactions return to the mempool. Within a tenure there is no open weight-based choice; blocks need a 70% signer threshold, and the chain halts while signers disagree.
Qualifications
- System class · Contested. Stacks' docs call it a Bitcoin L2 that settles with Bitcoin finality and argue it differs from sidechains because consensus runs on Bitcoin and hashes are published there. This profile treats it as a sidechain because it has its own producers and approvers and a signer-held BTC peg, and Bitcoin cannot check its transactions. Both readings agree it is not a rollup.
- Scarce resource · Partial. Stacks calls its design Proof of Transfer. Two resources are involved: miners spend BTC to win sortitions (under PoX-5 it funds staker rewards) and stakers lock STX that weights signer approval. Neither is plain proof of work or proof of stake.
- Finality · Partial. Confidence is staged: a signer-approved block arrives within seconds; the tenure's starting state is written to Bitcoin at the next Bitcoin block; after that, reversal needs a Bitcoin reorganization, which stays probabilistic. Transactions that depend on Bitcoin events, such as sBTC deposits, become invalid if those events are reorganized away.
- Slashing · Not applicable. Proof of Transfer has no slashing: locked STX is never destroyed or seized, and a signer that fails to perform forfeits rewards only.
Tradeoffs
- Emphasizes
- Security and Scalability Contested
- Gives up
- Decentralized block production and custody: a small group of miners competes for each tenure, blocks stop if signers holding 70% of weight cannot agree, and BTC moved into Stacks as sBTC is held by a selected signer set rather than secured by Bitcoin consensus.The security corner reflects Stacks' own framing that reversing an anchored transaction requires reorganizing Bitcoin. Bitcoin does not validate Stacks state, signers are not slashed for misbehaviour, and transactions that depend on Bitcoin events can be invalidated by Bitcoin reorganizations, so this reading is contested. Scalability here means fast blocks and contract execution kept off Bitcoin, not a measured throughput.
- Full node at home
- Practical at home 16Stacks docs list 2 vCPU, 8 GB RAM and a 2 TB disk for a Stacks node, or 16 GB RAM when also running the Bitcoin node it needs, which takes about 1 TB more disk. Uncompressed chainstate is about 1.2 TB and keeps growing; pruned snapshots of about 120 GB are called experimental. Because a Stacks node must follow both chains, the Bitcoin node's needs add to its own.
- Throughput claims
- No classified figure recorded
Scaling layers
- Stacks Subnets (formerly Hyperchains) · Sidechain, status unknown 2829
Subnet blocks are issued by a fully trusted pool of miners using a two-phase commit, and those miners control withdrawals back to Stacks; users can validate but cannot force an exit. Not a rollup. The last commit on the repository's default branch is dated 18 July 2023, and current Stacks docs do not cover subnets, so no live deployment was verified.
Capabilities
| Capability | How it is provided | Notes and sources |
|---|---|---|
| Account abstraction | Structured assessment pending | Not yet assessed for any chain. |
| Atomic swaps | Unknown | Not yet assessed under the current definitions; Clarity contracts can check a Merkle proof that a specific Bitcoin transaction was mined and release Stacks assets in response, a building block for contract-enforced swaps between BTC and Stacks assets. No built-in swap mechanism, and no live swap tool built on these contracts, was reviewed; Bitcoin reorganizations can invalidate such transactions. 71315 |
| Authenticated data publication | Unknown | Not yet assessed under this row's current definition. |
| Light clients | Unknown | Not yet assessed under the current definitions; no light-client or compact verification path for Stacks itself was found in current docs. Clarity's ability to verify Bitcoin transaction proofs verifies Bitcoin inside Stacks, not Stacks. 15 |
| Native staking or delegation | Structured assessment pending | Not yet assessed for any chain. |
| On-chain governance | Structured assessment pending | Not yet assessed for any chain. |
| Parallel execution | Structured assessment pending | Not yet assessed for any chain. |
| Payment or state channels | Unknown | No payment or state channel layer anchored to Stacks was verified. |
| Programmable spending | Native (protocol or core-team software) Earlier definition | Clarity contracts are interpreted and decidable, can read Bitcoin data, and transactions can carry post-conditions that abort if more assets move than the user allowed. Clarity contracts execute on Stacks nodes. 1314 |
| Protocol-verified messaging | Structured assessment pending | Not yet assessed for any chain. |
| Reversible transfers or recovery | Unknown | Not yet assessed under the current definitions; the earlier review found no protocol feature in the reviewed docs for cancelling, delaying or recovering Stacks payments. The sBTC deposit format lets a depositor reclaim BTC through a timelocked path if signers do not act; that is a safety path for peg deposits, not a feature for Stacks transfers. 20 |
| Rollups | Unknown | No rollup anchored to Stacks was verified. Stacks Subnets rely on a fully trusted miner pool that controls withdrawals, so they are not rollups, and their code appears dormant. 2829 |
| Shielded transfers | Structured assessment pending | Not yet assessed for any chain. |
| Signed partial offers | Unknown | Not yet assessed under this row's current definition. |
Reading these values
- How this feature is provided
- Built into the protocol, core-team software or independent software says where a feature lives and who can change it. These are implementation layers, not quality: core-team software is not closer to the protocol than independent software.
- Structured assessment pending
- The shared review has not assessed this feature for any chain yet (Account abstraction, Native staking or delegation, On-chain governance, Parallel execution, Protocol-verified messaging and Shielded transfers). That does not mean it is absent, and a chain’s profile may already describe it.
- Unknown
- The review has not established this for this chain under the current definition; the note beside it says why. Unknown is not absent and not a low score. A feature reads “Not present” only when a source shows it is absent.
- Earlier definition
- Payment or state channels, Programmable spending and Rollups keep the earlier definition until the next fact-check. There, “Native” does not separate the protocol from core-team software, “Ecosystem software” does not say who publishes it, and “Partial” does not say which layer.
- Reading across rows
- The list of capabilities is incomplete. Do not read these rows as a chain leading or lagging overall.
Ecosystem & custody
| Product type | Status | Notes and sources |
|---|---|---|
| Automated market makers | Established in the ecosystemALEX, Bitflow | ALEX documents an AMM on Stacks whose pool curve ranges from constant product to constant sum; Bitflow documents a Stacks DEX with an aggregator across pools. Liquidity depth was not measured and other venues were not reviewed. 3031 |
| Issuer-native stablecoins | First-partyUSDCx (issued through Circle xReserve) | USDCx is a Stacks token backed 1:1 by USDC held in a Circle-deployed xReserve contract. Circle describes it as issued by Stacks, not as Circle-issued USDC, and Circle's native USDC address list does not include Stacks. Stacks docs say Circle's xReserve attests deposits and minting, while Circle's transfer services handle movement between chains. 22232425 |
| Algorithmic stablecoins | None found | No algorithmic stablecoin with material usage was verified. Other dollar tokens issued on Stacks exist: Arkadiko's USDA is minted against locked collateral with liquidation and redemption, and Hermetica's USDh is backed by BTC paired with a short perpetual futures hedge. Neither is algorithmic in the narrow sense, and their usage was not measured. 3233 |
| Bridges | First-partysBTC peg (BTC to and from Stacks), USDCx via Circle xReserve | sBTC is a Stacks token redeemable 1:1 for BTC held in one Taproot address controlled by the sBTC signers; deposits complete within a few Bitcoin blocks and withdrawals wait for six Bitcoin confirmations. USDCx moves between Stacks and other chains through Circle xReserve attestations. Other bridges were not reviewed. Risk: sBTC holders trust the signer set: signatures from 70% of signers move the peg's BTC. The docs describe 15 initial signers while the signer page names 11 organizations, and they do not say what happens if a threshold colludes or loses keys. Deposits have a timelocked reclaim path; withdrawals depend on signers acting. USDCx depends on Circle's attestation service and the Stacks token contract. 17181920212224 |
| Block explorers | Established in the ecosystemStacks Explorer by Hiro | Stacks docs list the Hiro-built explorer for mainnet and testnet. STXER, a developer-oriented Stacks explorer, was also found, but its operator was not identified, so it is not counted here. Explorer data is provider-indexed, not consensus. 123435 |
| Hardware wallets | Established in the ecosystemLedger | See custody rows: Ledger announced STX send and receive in its own app in 2023, and Leather and Xverse, which both handle Stacks accounts, advertise Ledger support on their own sites. Trezor states it does not support Stacks. 36383940 |
Hardware-wallet custody
| Device maker | Status | What users can and cannot do |
|---|---|---|
| Ledger | Native supportSame as native: Unknown | Can: Create a Stacks account in Ledger's desktop and mobile app and send and receive STX with keys kept on the device (Ledger's 2023 announcement) Can: Delegate STX for stacking by signing on the device through a paired third-party wallet, as Ledger's staking guide describes Can: Use a Ledger device with third-party wallets such as Leather or Xverse, which advertise Ledger support; which Stacks and sBTC actions work with a Ledger account there was not checkedLedger's Stacks coin page returned 404 in this review and its staking guide still names the older Hiro wallet, so current coverage in Ledger's app, including stacking and sBTC, was not re-verified. 36373940 |
| Trezor | None foundSame as native: No | Cannot: Manage Stacks (STX) accounts with a Trezor device; Trezor's own page says it does not support Stacks 38 |
Public data
iKnow Blockchain has no public-data lookups for Stacks yet. This is a limit of the service, not a statement about the network.
| Lookup | Status | What it covers and its limits |
|---|---|---|
| Address or account | Not available yet | Public-data lookups for this chain are not built yet. |
| Tokens and assets | Not available yet | Public-data lookups for this chain are not built yet. |
| NFTs | Not available yet | Public-data lookups for this chain are not built yet. |
| Transactions | Not available yet | Public-data lookups for this chain are not built yet. |
Sourced developments
Developments: Review overdue Reviewed Sep 27, 2026; next review was due Oct 7, 2026, 12:00 UTC.
Publication date · newest first
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stacks-core 4.0.4 release ships inactive Clarity 7 code for a future Epoch 4.1
A maintenance release of the Stacks node and signer software that works with existing 4.0.x chainstate. It fixes signer block-validation, reorg and tenure-extension handling, removes the transaction-replay settings from signer and miner configuration, and adds Bitcoin signet support. It also ships Clarity 7 and other contract rules that apply only from Epoch 4.1; the notes give no height, date or SIP for that epoch.
- Implementation:released; Epoch 4.1 and Clarity 7 code included but inactive
- Release:stable release 4.0.4; recommended for node and signer operators
- Activation:no network activation; Epoch 4.1 activation height not stated
Sources: Stacks core contributors (GitHub) — stacks-core release 4.0.4 (external site) · Stacks core contributors (GitHub) — stacks-core releases (Atom feed) (external site)
-
First Bitcoin bond period (Genesis Bond) opened
Stacks Labs reported that the first institutional bond period closed with 250 BTC locked by standard Bitcoin scripts alongside STX, with four named institutions taking part and a second bonding period opening with limited capacity.
- Implementation:first bond period filled
- Release:live for allowlisted participants
- Activation:second bonding period registration open with limited capacity
Source: Stacks Labs — The Genesis Bond Is Live: Institutions Begin Bitcoin Staking on Stacks (external site)
-
stacks-core 4.0.2 node and signer release
A maintenance release of the Stacks node and signer software that works with existing 4.0.x chainstate. Miners must now name an existing Bitcoin Core wallet in their configuration, a change the notes tie to Bitcoin Core 31 and later. It also cuts Clarity memory use, makes signers reject unknown configuration fields, and carries two contract-rule fixes that apply only from a later Epoch 4.1.
- Implementation:Released
- Release:stable release 4.0.2; optional but recommended
- Activation:no network activation; its Epoch 4.1-gated fixes wait for an activation height the notes do not give
Sources: Stacks core contributors (GitHub) — stacks-core release 4.0.2 (external site) · Stacks core contributors (GitHub) — stacks-core releases (Atom feed) (external site)
-
PoX-5 hard fork activated at Bitcoin block 960,230
Stacks activated Epoch 4.0, bringing PoX-5 (SIP-045) and Clarity 6 (SIP-044). The change added Bitcoin bonds that pair BTC with locked STX, removed most staking cooldown cycles, sent miner BTC into a reward pool converted to sBTC instead of paying stakers' Bitcoin addresses directly, and restored the 1,000 STX coinbase.
- Proposal:SIP-044 and SIP-045 approved by community vote (reported 21 July 2026)
- Implementation:implemented in stacks-core 4.0.1
- Release:stacks-core 4.0.1 released 15 July 2026 as a mandatory upgrade
- Activation:active from Bitcoin block 960,230, reached 30 July 2026
Sources: Stacks Labs — The Stacks PoX-5 Hardfork Is Live: What Comes Next (external site) · Stacks Labs — SIP-044 and SIP-045 Approved: Bitcoin Staking Is Ratified (external site) · Stacks Improvement Proposals (stacksgov) — SIP-045: PoX-5 Bitcoin Staking (external site) · Stacks core contributors (GitHub) — stacks-core release 4.0.1 (external site) · Stacks Foundation — Stacks 4.0.1 Network Upgrade - Clarity 6 & Bitcoin Staking (Hard Fork) (external site) · Stacks Documentation — Epoch 4.0 Consensus Changes (external site)
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USDCx launched on Stacks through Circle xReserve
A USDC-backed dollar token, USDCx, went live on Stacks, issued through Circle's xReserve and moving between Ethereum and Stacks at launch. Circle describes it as issued by Stacks, not as Circle-issued USDC.
- Implementation:Deployed
- Release:live on mainnet
- Activation:Ethereum route live at launch; other chains were on the roadmap
Sources: Stacks Labs — USDCx Launches on Stacks (external site) · Circle — USDCx on Stacks now available via Circle xReserve (external site) · Circle — xReserve (external site)
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Clarity 4 activated on Stacks mainnet
SIP-033 and SIP-034 activated at Bitcoin block 923,222, bringing Clarity 4 with functions for checking another contract's code hash, restricting a contract's own asset movements, reading block time and verifying secp256r1 signatures, plus finer-grained tenure budget extensions.
- Proposal:SIP-033 and SIP-034 approved
- Implementation:Released
- Release:Activated
- Activation:active from Bitcoin block 923,222
Sources: Stacks Labs — Clarity 4 is Now LIVE (external site) · Stacks Documentation — Latest Updates (external site)
Topics your AI can explain
Your AI can explain these topics for Stacks through the connection, with sources.
Known gaps
What this profile's review did not establish:
- No throughput figure is listed; no primary-source rate was classified for this profile.
- Whether Stacks is a Bitcoin layer 2 or a sidechain is contested; this profile files it as a sidechain for the reasons in its class note.
- The size, independence and uptime of the active block-signer set were not measured; miner concentration is known only from the docs' statement of at least 4-5 miners.
- Stacks docs disagree on the sBTC signer count: 15 initial signers on the overview and security pages, 11 organizations named on the signer page.
- The docs do not describe what happens to sBTC holders if a signer threshold colludes, loses keys or stops operating.
- Ledger's Stacks coin page returned 404; Ledger support rests on a 2023 announcement and a staking guide naming the older Hiro wallet, so current app coverage, stacking and sBTC support were not re-verified.
- Third-party bridges such as Allbridge-bridged USDC or ALEX's Brotocol, and venues other than ALEX and Bitflow, were not reviewed; liquidity depth was not measured.
- No light-client or compact verification path for Stacks itself was found.
- No payment channel, state channel or rollup anchored to Stacks was verified; the last commit on the Stacks Subnets default branch is dated July 2023.
- The stxscan.co domain redirected to an unrelated site during this review, so it was not counted as an explorer; STXER's operator was not identified.
- Whether a pruned or remote Bitcoin node is enough for a Stacks follower node was not confirmed.
- The older Gaia storage system is absent from current docs and was not reviewed for the data-publication capability.
- The PoX-5 overview in the Stacks docs says its material was being merged into older pages throughout August 2026; some reviewed pages may describe earlier rules.
- Node software released in September 2026 carries code for a later network upgrade and a new contract-language version whose activation height was not confirmed.
- Total STX supply and long-run emission beyond the current 1,000 STX per Bitcoin block coinbase were not verified.
Sources
Oldest dated source check: Source checked Sep 27, 2026 Next check due Oct 27, 2026.
- What Is Stacks? (external site)
- The Bitcoin Connection (external site)
- Proof of Transfer (external site)
- How Are Blocks Mined? (external site)
- Signing: Verifying Block Validity (external site)
- Bitcoin Finality (external site)
- Bitcoin Reorgs (external site)
- What was the Nakamoto Upgrade? (external site)
- Staking: How STX Holders Contribute (external site)
- Technical Specifications (external site)
- Wallets & Accounts (external site)
- Mainnet and Testnets (external site)
- Clarity (external site)
- Post Conditions (external site)
- Verifying Bitcoin Transactions in Clarity (external site)
- Run a Node (external site)
- sBTC (external site)
- Security Model of sBTC (external site)
- The sBTC Signers (external site)
- Pegging in sBTC (external site)
- Pegging out sBTC (external site)
- USDCx (external site)
- USDCx on Stacks now available via Circle xReserve (external site)
- xReserve (external site)
- USDC Contract Addresses (external site)
- SIP-045: PoX-5 Bitcoin Staking (external site)
- The Genesis Bond Is Live: Institutions Begin Bitcoin Staking on Stacks (external site)
- stacks-subnets (external site)
- stacks-subnets commits on develop (external site)
- Trading Pool (external site)
- Bitflow documentation (external site)
- Arkadiko protocol overview (external site)
- How it Works (USDh) (external site)
- Stacks Explorer by Hiro (external site)
- Stacks Explorer for devs (STXER) (external site)
- Stacks (STX) Joins Ledger Live (external site)
- Stacks staking with Ledger (external site)
- Stacks support (external site)
- Leather wallet (external site)
- Xverse wallet (external site)
Report an error
Found something wrong or out of date? Reporting is free, and every chain goes through the same process. Published corrections appear in the public log.
Funding disclosure
Funding disclosures appear here when an upkeep arrangement exists, in the form “Upkeep funded by [name]; verdicts unaffected.” The funder ledger has not been published yet. Neutrality & funding