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https://californiabitcoin.org/api/agent/v1/coveragehttps://californiabitcoin.org/api/agent/v1/sourceshttps://californiabitcoin.org/openapi.jsonAdoption
2 maintained conceptsEl Salvador and BitcoinEl Salvador made Bitcoin legal tender in 2021, becoming the first nation to adopt Bitcoin at the national legal-tender level.Merchant Bitcoin paymentsBusinesses can accept Bitcoin on-chain or over Lightning, with choices around custody, conversion, accounting, and payment tooling.
Cryptography
6 maintained conceptsCryptographic hash functionsA cryptographic hash maps arbitrary data to a fixed-size digest and is designed to resist collisions and reversal.Digital signaturesDigital signatures let a private-key holder authorize data in a way others can verify with the corresponding public key.Merkle treesMerkle trees summarize many pieces of data into one root hash while allowing efficient proofs that an item is included.MuSig2MuSig2 is an interactive multisignature protocol that lets multiple signers jointly produce one BIP340-compatible Schnorr signature for an aggregated public key.Public-key cryptographyPublic-key cryptography lets people publish a key for verification or encryption while keeping a paired private key secret.Schnorr signaturesBIP340 defines Bitcoin's Schnorr signature scheme for Taproot key-path spending, using secp256k1 with a linear signature construction that also supports advanced key-aggregation protocols.
Custody
13 maintained conceptsBitcoin custodiansA custodian holds private keys or controls withdrawal authority on behalf of users, simplifying operations while introducing counterparty dependence.Bitcoin walletsA Bitcoin wallet manages keys, addresses, transaction construction, and often coin selection; bitcoin itself remains recorded on the network.Cold storageCold storage keeps Bitcoin signing keys on systems designed to remain isolated from internet-connected environments.Extended public keysAn extended public key can derive a branch of public keys and addresses without exposing the corresponding private spending keys.Hardware walletsHardware wallets are dedicated signing devices designed to keep private keys isolated while allowing users to authorize transactions.HD walletsHierarchical deterministic wallets derive many keys and addresses from a single seed using standardized derivation paths.Lost bitcoinBitcoin whose private keys are permanently lost may remain visible on-chain but become economically unspendable, reducing effective circulating supply.MultisignatureMultisignature spending conditions require more than one key to authorize spending, enabling redundancy and shared control.Private keysA private key is secret cryptographic material used to authorize spending from Bitcoin outputs controlled by the corresponding key conditions.Public keysA public key is derived from a private key and can be used to verify digital signatures without revealing the private key.Seed phrasesA seed phrase is a human-readable backup encoding used by many hierarchical deterministic wallets to recreate a wallet’s key material.Self-custodySelf-custody means controlling the private keys required to authorize spending rather than relying on a custodian.Watch-only walletsA watch-only wallet tracks addresses and balances without possessing the private keys needed to spend.
Cypherpunk era
2 maintained conceptsCrypto-anarchyCrypto-anarchist thinking argued that strong cryptography could enable private, censorship-resistant communication and exchange beyond traditional gatekeepers.CypherpunksCypherpunks were technologists and activists who believed privacy-enhancing cryptography should be built and deployed rather than merely discussed.
Development
2 maintained conceptsBitcoin testnetBitcoin testnet is a public network for testing Bitcoin software with coins intended to have no economic value; its chain and conditions can differ substantially from mainnet.SignetSignet is a Bitcoin test network whose blocks require an additional challenge solution, providing a more predictable testing environment than permissionless testnet while using valueless test coins.
Foundations
1 maintained conceptFundamentals
5 maintained conceptsBitcoinBitcoin is a peer-to-peer digital monetary network with a fixed issuance schedule, independent validation, and no central issuer.Censorship resistanceBitcoin is designed so valid transactions can be broadcast and settled without requiring approval from a central payment administrator.DecentralizationBitcoin decentralization comes from distributing validation, ownership, mining, development, and economic choice rather than assigning protocol control to one institution.Permissionless accessBitcoin allows anyone who can communicate with the network to run software, receive bitcoin, verify history, or attempt to mine without membership approval.SatoshisA satoshi, or sat, is the smallest native unit commonly represented in Bitcoin: one hundred millionth of a bitcoin.
History
14 maintained concepts2024 U.S. spot Bitcoin ETP approvalOn January 10, 2024, the SEC approved rule changes that allowed multiple U.S. spot Bitcoin exchange-traded products to begin trading.Bitcoin Cash splitBitcoin Cash split from Bitcoin in 2017 after disagreement over block-size and scaling policy, creating a separate network with incompatible consensus rules.Bitcoin in 2017In 2017 Bitcoin saw rapid global attention, the SegWit activation, the Bitcoin Cash split, the SegWit2x dispute, and a dramatic price cycle.Bitcoin Pizza DayOn May 22, 2010, Laszlo Hanyecz’s purchase of two pizzas for 10,000 BTC became the best-known early example of Bitcoin being used for a real-world purchase.Bitcoin white paperSatoshi Nakamoto published “Bitcoin: A Peer-to-Peer Electronic Cash System” on October 31, 2008, describing a way to transfer value without a trusted central intermediary.Blocksize WarThe Blocksize War was a multi-year dispute over how Bitcoin should scale and who ultimately determines the network’s rules, culminating in the 2017 SegWit activation and failure of SegWit2x.Genesis blockBitcoin’s genesis block is block 0, mined by Satoshi on January 3, 2009 and containing the Times headline about a second bank bailout.Mt. GoxMt. Gox was an early Bitcoin exchange that collapsed in 2014 after losing access to a large amount of customer bitcoin, becoming a landmark custody failure.Satoshi NakamotoBitcoin was created by a person or group using the pseudonym Satoshi Nakamoto. Satoshi published the Bitcoin white paper in 2008, released the first Bitcoin software in 2009, mined the genesis block, and worked with early contributors before stepping away around 2010–2011. Satoshi’s real-world identity remains unknown.Satoshi’s departureSatoshi gradually withdrew from public Bitcoin development and communication around 2010–2011, leaving the project to an open community.Silk RoadSilk Road was an online marketplace that used Bitcoin and brought early attention to the network, while also shaping years of public debate about illicit-use narratives.The 2020 halvingBitcoin’s third subsidy halving occurred in May 2020, reducing the block subsidy from 12.5 BTC to 6.25 BTC.The 2024 halvingBitcoin’s fourth subsidy halving occurred in April 2024, reducing the block subsidy from 6.25 BTC to 3.125 BTC.User-activated soft forkA user-activated soft fork is a coordination strategy in which economic nodes signal or enforce upgraded rules independent of miner activation.
Lightning
6 maintained conceptsBOLT 12 OffersBOLT12 Offers define reusable Lightning payment offers with invoice negotiation, route blinding, and flexible payment flows beyond one-time BOLT11 invoices.Lightning onion routingLightning uses layered onion-encrypted routing instructions so each forwarding node learns what it needs for its own hop rather than the complete route; this improves privacy but does not make all payment metadata anonymous.Lightning splicingLightning splicing uses an on-chain transaction to change channel funding while preserving channel continuity, allowing liquidity to be added to or removed from an existing channel workflow.Lightning watchtowersA Lightning watchtower monitors the chain on behalf of a client and can respond to an obsolete channel-state broadcast, helping protect users who cannot remain online continuously.Static channel backupsA static channel backup preserves enough channel information for supported Lightning implementations to attempt recovery after local data loss, but it is not a substitute for every form of channel-state backup.Submarine swapsSubmarine swaps use linked hashlocked conditions to exchange value between on-chain Bitcoin and Lightning, enabling liquidity movement while reducing the need to trust one counterparty to complete both settlement legs.
Markets
5 maintained conceptsBitcoin exchangesBitcoin exchanges match buyers and sellers or provide brokerage services, often while temporarily custodying customer bitcoin.Bitcoin market priceBitcoin’s market price is the exchange rate at which buyers and sellers currently trade bitcoin; price behavior is distinct from protocol behavior.Bitcoin volatilityBitcoin’s market price can move sharply because it trades continuously in a global market with changing liquidity, expectations, leverage, and adoption.ETF versus self-custodyA spot Bitcoin ETP offers brokerage convenience and delegated custody; self-custody offers direct key control and native access to the Bitcoin network.Spot Bitcoin ETPsU.S. spot Bitcoin exchange-traded products give investors regulated brokerage exposure to bitcoin held by custodians, without requiring direct self-custody.
Mining
14 maintained conceptsASIC minersASICs are specialized chips designed to perform Bitcoin’s SHA-256 proof-of-work hashing efficiently.Bitcoin energy useBitcoin mining uses energy to perform proof of work; evaluating it requires considering energy sources, grid context, security provided, and alternative uses.Bitcoin miningMining is the competitive process of constructing candidate blocks and searching for a valid proof of work.Bitcoin mining and renewablesBitcoin miners can operate where electricity is available, including renewable or curtailed energy, but the environmental profile varies by location and time.Block subsidyThe block subsidy is the newly issued bitcoin portion of a miner’s block reward; it declines through halvings over time.Coinbase transactionThe first transaction in a block is the coinbase transaction, which creates the block subsidy and collects that block’s fees for the miner.HalvingEvery 210,000 blocks, Bitcoin’s block subsidy is cut in half.HashrateHashrate estimates the amount of SHA-256 computation being performed by Bitcoin miners.Mining difficultyBitcoin adjusts proof-of-work difficulty every 2,016 blocks to target an average block interval of about ten minutes.Mining poolsMining pools coordinate hashpower from many miners and distribute rewards according to contributed work.Mining template selectionMining template selection is the process of choosing valid transactions and block fields for a candidate block; pool architecture can centralize this decision even when underlying hashpower is distributed.Proof of workProof of work requires miners to expend computation and energy to propose blocks, giving nodes an objective way to compare competing valid histories by accumulated work.Stranded energyStranded or curtailed energy is energy that cannot easily reach other buyers; portable mining loads can sometimes monetize it.Stratum V2Stratum V2 is a modern protocol suite for communication among miners and pools with encrypted transport and mechanisms designed to improve efficiency and miner participation in block-template selection.
Money
11 maintained conceptsBitcoin issuanceNew bitcoin enter circulation through the block subsidy paid to miners, according to a predetermined schedule.Bitcoin versus goldBitcoin and gold share scarcity and monetary use cases, but differ in physicality, verification, portability, issuance, custody, and settlement.Digital scarcityBitcoin creates digitally verifiable scarcity through consensus rules that prevent arbitrary issuance and double spending.Fiat moneyFiat money is currency whose monetary status depends primarily on government designation, institutions, and monetary policy rather than commodity convertibility.Fixed supplyBitcoin’s issuance rules converge on a terminal supply of roughly 21 million bitcoin.InflationInflation can refer to increases in the general price level or to expansion of a money supply; careful Bitcoin analysis should distinguish the meanings.Medium of exchangeA medium of exchange is something people commonly accept in trade, reducing the need for direct barter.Monetary premiumA monetary premium is the portion of an asset’s value attributable to its perceived usefulness for storing or transferring value rather than direct consumption.Store of valueA store of value is an asset people use to preserve purchasing power across time, though no asset can guarantee stable value over every horizon.Unit of accountA unit of account is the standard in which prices, debts, and economic calculations are expressed.Why 21 million?Bitcoin’s issuance parameters produce a supply that converges near 21 million BTC; the exact figure results from the initial subsidy, halving interval, and integer-denominated rewards.
Network
3 maintained conceptsBIP324 encrypted P2P transportBIP324 defines an encrypted version-2 transport for Bitcoin peer connections, protecting protocol messages from passive observation and making some forms of network manipulation more difficult without hiding peer IP addresses.Compact block relayBIP152 compact block relay reduces bandwidth and latency when propagating new blocks by sending short transaction identifiers and reconstructing most block contents from transactions peers already know.Package relayPackage relay is Bitcoin Core work for evaluating and relaying related groups of transactions together, improving fee-bumping and contract reliability when a transaction's economics depend on descendants or ancestors.
Nodes
1 maintained conceptPeople
1 maintained conceptPolicy
2 maintained conceptsKYCKnow-your-customer rules require many regulated financial businesses to collect and verify customer identity information.U.S. Strategic Bitcoin ReserveIn March 2025, the U.S. government established a Strategic Bitcoin Reserve for government-held bitcoin, marking a major shift in official treatment of the asset.
Pre-Bitcoin
6 maintained conceptsb-moneyWei Dai’s b-money proposal described an anonymous distributed electronic cash system and helped articulate ideas later echoed in Bitcoin.Bit GoldNick Szabo’s Bit Gold proposal described costly digital objects created through proof of work and linked records, anticipating several ideas later found in Bitcoin.David ChaumDavid Chaum pioneered privacy-preserving digital cash and blind signatures, showing that electronic money could be both cryptographic and privacy-aware.DigiCash and eCashDigiCash commercialized Chaumian digital cash, proving that cryptographic money could work technically even though the company itself did not become a lasting monetary network.HashcashHashcash is Adam Back’s proof-of-work system originally designed to deter email spam by requiring computational work.Reusable Proofs of WorkHal Finney’s RPOW system let proof-of-work tokens be transferred and reused through trusted computing hardware.
Privacy
8 maintained conceptsAddress reuseReusing Bitcoin addresses can make separate payments easier to link and generally weakens privacy.Bitcoin privacyBitcoin is pseudonymous rather than inherently anonymous; transaction history is public, making address reuse, metadata, custody, and network behavior important privacy considerations.Coin controlCoin control lets wallet users choose which UTXOs to spend, which can affect fees, privacy, and future wallet structure.CoinJoinCoinJoin is a collaborative transaction technique in which multiple users combine inputs and outputs to make straightforward ownership heuristics less reliable.Compact block filtersBIP157 and BIP158 define compact block-filter protocols that let lightweight clients identify potentially relevant blocks without revealing a precise list of wallet addresses to a remote server.Network privacyNetwork-level privacy concerns how transaction broadcasts, IP metadata, and node connectivity can reveal information beyond the blockchain itself.PayjoinBIP78 Payjoin is an interactive payment construction in which the receiver contributes an input, breaking common-input ownership assumptions and improving transaction privacy without requiring a large coordinated CoinJoin round.Silent PaymentsBIP352 defines reusable non-interactive payment addresses that let senders derive unique Taproot outputs, reducing address reuse without requiring the recipient to run an interactive payment server.
Protocol
21 maintained conceptsBitcoin blocksBlocks package transactions together with metadata and proof of work, extending Bitcoin’s shared transaction history.Bitcoin CoreBitcoin Core is the most widely used Bitcoin full-node implementation and descends from Satoshi’s original open-source software.Bitcoin covenantsA Bitcoin covenant constrains some property of future spending rather than only specifying who can authorize the current spend; proposed covenant mechanisms differ significantly in scope, complexity, and consensus tradeoffs.Bitcoin forksA fork can mean a temporary chain split, a software divergence, or a persistent network split caused by incompatible rules; the context matters.Bitcoin Improvement ProposalsBIPs are design documents for proposing, documenting, and coordinating Bitcoin standards and protocol changes.Bitcoin nodesFull nodes independently verify blocks and transactions against the consensus rules they choose to enforce.Bitcoin ScriptBitcoin Script is Bitcoin’s limited scripting system for specifying the conditions under which transaction outputs can be spent.Block heightBlock height is the number of a block in Bitcoin’s chain, counting upward from the genesis block.BlockchainBitcoin’s blockchain is an ordered history of proof-of-work-secured blocks, each committing to transactions and the previous block.Chain reorganizationsA reorganization occurs when a node switches from one valid chain tip to another chain with more accumulated proof of work.Consensus rulesConsensus rules define which blocks and transactions a Bitcoin node will accept as valid.Consensus versus policyConsensus rules determine validity; relay and mempool policies guide what nodes relay or temporarily store without redefining validity.Discreet Log ContractsDiscreet Log Contracts use adaptor-signature techniques and oracle attestations so parties can settle a Bitcoin contract based on an external outcome without placing the full contract logic on-chain.Hard forksA hard fork changes rules in a way that can make blocks valid under the new rules invalid to nodes following the old rules.MiniscriptMiniscript is a structured language for a useful subset of Bitcoin Script that makes complex spending policies easier for software to analyze, compose, satisfy, and estimate.Open-source developmentBitcoin software is open source, allowing anyone to inspect, propose changes, build alternatives, and choose what software to run.Ordinals and inscriptionsOrdinals theory numbers individual satoshis and enabled inscriptions of arbitrary data into Bitcoin witness data, creating new uses and block-space demand.RunesRunes is a fungible-token protocol implemented using Bitcoin transactions and launched around the 2024 halving.Segregated WitnessSegWit separated signature data from the legacy transaction serialization, fixing transaction malleability and enabling more efficient block-space accounting.Soft forksA soft fork tightens Bitcoin’s validity rules in a way that can remain compatible with older nodes that continue to enforce the previous broader rules.TaprootTaproot upgraded Bitcoin with Schnorr signatures and a more private and efficient way to express complex spending conditions.
Scaling
8 maintained conceptsBitcoin layer twoLayer-two systems seek to add capabilities above Bitcoin’s base layer while using Bitcoin for settlement, security anchoring, or asset backing to varying degrees.Bitcoin sidechainsSidechains are separate blockchains connected to Bitcoin through some form of peg or federation, enabling different tradeoffs and functionality.FederationsA federation is a defined set of entities that jointly operate a system or custody arrangement, used in some Bitcoin-adjacent protocols and sidechains.HTLCsHash time-locked contracts enable conditional payments that can be securely routed across multiple Lightning channels.Lightning liquidityLightning payments depend on usable inbound and outbound channel capacity along a route, so liquidity management is central to reliable payments.Lightning NetworkLightning uses bidirectional payment channels and routed off-chain payments to enable fast, low-value transactions that ultimately settle to Bitcoin.On-chain versus LightningOn-chain transactions settle directly in Bitcoin blocks; Lightning transactions occur through payment channels and can later settle on-chain.Payment channelsA payment channel lets participants update balances off-chain while retaining the ability to settle the latest valid state on Bitcoin.
Script
2 maintained conceptsCHECKLOCKTIMEVERIFYBIP65 CHECKLOCKTIMEVERIFY lets Bitcoin Script require an output to remain unspendable until an absolute block height or time condition is satisfied.CHECKSEQUENCEVERIFYBIP112 CHECKSEQUENCEVERIFY works with relative locktime semantics to let scripts require a spend to wait for a relative number of blocks or time after the spent output confirms.
Security
2 maintained concepts51% attacksA miner or coalition with majority hashpower can potentially reorganize recent blocks or censor transactions, but cannot arbitrarily create bitcoin or spend coins without valid signatures.Quantum computing and BitcoinLarge fault-tolerant quantum computers could threaten some public-key cryptography, but practical attacks on Bitcoin at scale are not currently available and migration paths can be considered if the threat matures.
Transactions
16 maintained conceptsBech32 addressesBech32 is a human-readable address encoding used for native SegWit outputs; Bech32m is used for Taproot and later witness versions.Bitcoin addressesBitcoin addresses are human-facing encodings of spending destinations or script commitments, not permanent account identifiers.Child pays for parentChild-pays-for-parent fee bumping uses a high-fee child transaction to raise the combined package feerate of an unconfirmed parent and child so miners have more incentive to confirm both.ConfirmationsA transaction gains confirmations as blocks are added after the block containing it, increasing the work an attacker would need to reorganize that history.Double spendingA double spend is an attempt to spend the same bitcoin output more than once. Bitcoin’s validation rules and proof-of-work ordering resolve conflicting spends.Dust outputsDust is a policy concept for outputs whose value is uneconomical relative to the cost of spending them under relay policy; dust thresholds are not a consensus rule defining a minimum Bitcoin amount.Fee bumpingFee bumping increases the incentive for miners to confirm an unconfirmed payment, commonly through replace-by-fee or child-pays-for-parent depending on who can construct the relevant replacement or child transaction.Inputs and outputsBitcoin transactions consume previous outputs as inputs and create new outputs assigning spendable value to new conditions.MempoolA node’s mempool is its local collection of valid unconfirmed transactions waiting to be mined.nLockTimeA transaction's nLockTime field can delay its finality until a specified block height or timestamp, subject to transaction sequence semantics and node policy.Replace-by-feeBIP125 opt-in replace-by-fee allows an unconfirmed transaction that signals replaceability to be replaced by a conflicting transaction paying a higher effective fee under node policy rules.Signature hash typesBitcoin signature hash modes determine which transaction fields a signature commits to, enabling different transaction-coordination patterns while requiring careful wallet and protocol handling.Transaction feesBitcoin transaction fees are bids for scarce block space and are primarily determined by transaction size in virtual bytes and current demand.Transaction malleabilityTransaction malleability is the ability for some transaction data to be changed without invalidating its economic effect; SegWit fixed important third-party txid malleability for SegWit spends and enabled more reliable payment-channel designs.Transaction sequenceBitcoin transaction input sequence values participate in relative locktime and replacement semantics, including BIP68 relative timelocks and replaceability signaling under BIP125 policy.UTXOBitcoin tracks spendable transaction outputs rather than account balances. Wallets spend existing outputs and create new ones.
Wallets & custody
7 maintained conceptsBIP39 passphraseA BIP39 passphrase is optional input combined with mnemonic words during seed derivation; every passphrase produces a valid-looking but different seed, so loss or error can make the intended wallet unrecoverable.Bitcoin vaultsBitcoin vaults are custody designs that use preplanned paths, delays, key separation, or covenant-like restrictions to create time or policy barriers around withdrawals and improve recovery options after compromise.Coin selectionCoin selection is the wallet process of choosing which UTXOs to spend, balancing fees, change, future spend cost, and privacy implications such as unnecessary ownership linkage.Output descriptorsBitcoin output descriptors are a standardized language for describing sets of scripts and keys a wallet can watch or spend, improving wallet interoperability and backup clarity.Partially Signed Bitcoin TransactionsBIP174 PSBT is a standard container for passing unsigned or partially signed transaction data among coordinators, wallets, hardware signers, and other tools without requiring every participant to construct or broadcast the transaction.PSBT version 2BIP370 PSBTv2 reorganizes transaction-construction fields so participants can modify transaction inputs and outputs without embedding a complete unsigned transaction in the global map.Wallet fingerprintsWallet and master-key fingerprints are short identifiers used by wallet standards and PSBT workflows to help identify key origins; they are identifiers, not secret authentication factors.