Read the Bitcoin WhitepaperView on GitHub Study modeFoundationsExpand all01What is Bitcoin?02Who invented Bitcoin and when?03What problem does Bitcoin solve?04What is a Bitcoin "node"?05What is a "miner"?06What is a wallet?07Where do new bitcoins come from?08What's the maximum supply?09What is a "satoshi"?HashesExpand all01What is a cryptographic hash function?02Which hash function does Bitcoin use most?03What is the avalanche effect?04Why double-SHA256?05What is HASH160?Keys & ECDSAExpand all01What curve does Bitcoin use?02What is a private key?03What is a public key?04What is the discrete log problem?05What is ECDSA in one sentence?06What is RFC 6979?07What happens if a nonce kkk is reused across two ECDSA signatures?08What is "low-s" malleability?09What is DER encoding?AddressesExpand all01What is a P2PKH address?02How is a P2PKH address derived from a pubkey?03What is Base58Check?04Why Base58, not hex or Base64?05What does the version byte do?Transactions & UTXOExpand all01What is a UTXO?02What is a transaction input?03What is a transaction output?04How does a transaction transfer ownership?05What is a coinbase transaction?06What is the transaction fee?07What is coinbase maturity?08What is a txid?09What is a varint?ScriptExpand all01What is Bitcoin Script?02Why isn't Bitcoin Script Turing-complete?03What's the difference between scriptSig and scriptPubKey?04What does a P2PKH scriptPubKey look like?05What does a P2PKH scriptSig look like?06What does OP_CHECKSIG do?07What is P2SH?08What is multisig?09Why must OP_CHECKMULTISIG spends prepend a dummy stack element?Sighash & MalleabilityExpand all01What is the "sighash"?02What is SIGHASH_ALL?03How is the legacy SIGHASH_ALL preimage built?04What is missing from the legacy sighash preimage?05What is transaction malleability?06What is BIP-66?Blocks & MerkleExpand all01What is a Bitcoin block?02What's in a block header?03What is a merkle tree?04What is CVE-2012-2459?05Why is the block timestamp loose?Proof of WorkExpand all01What is proof-of-work?02What is the proof-of-work "target"?03What is the nonce in a block header?04How is difficulty adjusted?05Why 10 minutes per block?06What is the current block subsidy (2026)?Blockchain & ConsensusExpand all01What is the "longest chain" rule?02What is a chain reorg?03What's the difference between a soft fork and a hard fork?04What is "undo data" that a node stores when applying a block?05What is a 51% attack?06What is "finality" in Bitcoin?Economics & MempoolExpand all01What is the mempool?02What is "feerate"?03What is "replace-by-fee" (RBF)?04What is the "security budget"?05What happens to mining incentives after 2140?06How does difficulty enforce a mining equilibrium?Monetary Policy & AdoptionExpand all01What is Bitcoin's current annual inflation rate?02How many bitcoins are estimated to be lost forever?03What's encoded in the genesis block's coinbase?04When were US spot Bitcoin ETFs approved?05What is the Cantillon effect, and why is it cited by Bitcoiners?06Why is the 21M cap credible, beyond "the code says so"?Famous IncidentsExpand all01What was the value-overflow incident (August 2010)?02What was the March 2013 fork?03What was the PS3 ECDSA hack (2010)?04What was Mt. Gox?05What was CVE-2018-17144?Modern BitcoinExpand all01What is SegWit?02What is BIP-143?03What is Taproot?04What is Schnorr signing?05What is the Lightning Network?06What is a covenant in Bitcoin?07How does quantum computing threaten Bitcoin?