# 21 BTC

> Bitcoin-only information platform: live market and network data (price, ETF flows, on-chain metrics, holders, Lightning, nodes), beginner guides and short explainer videos, a Bitcoin wiki, museum and blog. The whole site is available in English and Russian (add ?lang=ru). Home, Learn, Calendar and Price are also translated into Thai, Spanish, Chinese and Arabic (add ?lang=th, es, zh or ar); other pages in those languages show English. Nothing on the site is investment advice.

## Languages
- English (default): https://21btc.cc/
- Русский (Russian): https://21btc.cc/?lang=ru
- ไทย (Thai): [ข้อมูล Bitcoin: ราคา กระแสเงิน ETF ออนเชน เครือข่าย](https://21btc.cc/?lang=th)
- ไทย (Thai): [เรียนรู้ Bitcoin จากศูนย์: คู่มือ อภิธานศัพท์ คำถามที่พบบ่อย ความปลอดภัย](https://21btc.cc/learn?lang=th)
- ไทย (Thai): [ปฏิทิน Bitcoin: วันสำคัญ นับถอยหลังฮาล์วิง งานประชุม](https://21btc.cc/calendar?lang=th)
- ไทย (Thai): [ราคา Bitcoin ใน 20 สกุลเงิน: USD, EUR, CAD, INR, KRW และอื่น ๆ](https://21btc.cc/price?lang=th)
- Español (Spanish): [Datos de Bitcoin: precio, flujos de ETF, on-chain y red](https://21btc.cc/?lang=es)
- Español (Spanish): [Aprende Bitcoin desde cero: guías, glosario, preguntas y seguridad](https://21btc.cc/learn?lang=es)
- Español (Spanish): [Calendario de Bitcoin: fechas clave, cuenta atrás del halving, conferencias](https://21btc.cc/calendar?lang=es)
- Español (Spanish): [Precio de Bitcoin en 20 divisas: USD, EUR, CAD, INR, KRW y más](https://21btc.cc/price?lang=es)
- 中文 (Chinese): [Bitcoin 比特币数据：价格、ETF 资金流、链上、网络](https://21btc.cc/?lang=zh)
- 中文 (Chinese): [从零学习 Bitcoin 比特币：指南、术语表、常见问题、安全](https://21btc.cc/learn?lang=zh)
- 中文 (Chinese): [Bitcoin 比特币日历：重要日期、减半倒计时、会议](https://21btc.cc/calendar?lang=zh)
- 中文 (Chinese): [Bitcoin 比特币价格（20 种货币）：USD、EUR、CAD、INR、KRW 等](https://21btc.cc/price?lang=zh)
- العربية (Arabic): [بيانات Bitcoin: السعر وتدفقات ETF وبيانات السلسلة والشبكة](https://21btc.cc/?lang=ar)
- العربية (Arabic): [تعلّم Bitcoin من الصفر: أدلة ومسرد وأسئلة شائعة وأمان](https://21btc.cc/learn?lang=ar)
- العربية (Arabic): [تقويم Bitcoin: التواريخ المهمة والعدّ التنازلي للتنصيف والمؤتمرات](https://21btc.cc/calendar?lang=ar)
- العربية (Arabic): [سعر Bitcoin بـ 20 عملة: USD وEUR وCAD وINR وKRW وغيرها](https://21btc.cc/price?lang=ar)

## Key sections
- [Bitcoin network live: hashrate, difficulty, fees, halving](https://21btc.cc/network): Live bitcoin block height, hashrate chart, next difficulty adjustment, fee rates, mempool size and countdown to the 2028 halving.
- [Learn bitcoin from zero: guides, glossary, FAQ, security](https://21btc.cc/learn): Bitcoin from zero, a glossary and FAQ, plus security guides: seed backups, multisig, inheritance, verifying wallets and running your own node.
- [Bitcoin Rainbow Chart and 4-year halving cycles](https://21btc.cc/cycles): Rainbow chart on real price history, halvings, cycle tops and bottoms, drawdowns and all cycles side by side. Educational, not advice.
- [US spot bitcoin ETF flows today: IBIT, FBTC, GBTC and more](https://21btc.cc/etf): Daily net flows for every US spot bitcoin ETF, cumulative inflows since January 2024 and how much BTC the funds hold.
- [Compare US spot bitcoin ETFs: fees, holdings, flows](https://21btc.cc/etf/compare): Every pair of 12 US spot bitcoin ETFs side by side: yearly fee, BTC held, 20-day flows and custodian, updated daily from Farside. Not investment advice.
- [Bitcoin on-chain indicators: MVRV, NUPL, SOPR, power law, S2F](https://21btc.cc/onchain): MVRV, realized price, NUPL, SOPR, LTH/STH, power law, stock-to-flow, Mayer multiple, 200-week MA and Puell multiple, explained simply.
- [Who holds bitcoin: companies, ETFs, governments, exchanges](https://21btc.cc/holders): Bitcoin held by public and private companies, ETFs and funds, governments and exchanges, with the largest holders and 7-day changes.
- [Bitcoin Lightning Network: how it works, live stats, wallets, nodes](https://21btc.cc/lightning): Everything about the Bitcoin Lightning Network: channels, HTLCs, invoices (BOLT11, BOLT12, LNURL, Lightning Address), live capacity and fees, top nodes, LND/CLN/Eclair/LDK, wallets, LSPs, L402 for AI agents, zaps, risks and guides.
- [Bitcoin nodes online: live count, countries, Core vs Knots, solar node](https://21btc.cc/nodes): How many Bitcoin nodes are reachable right now: trend, Tor/IPv4/I2P share, countries, Bitcoin Core and Knots versions, OP_RETURN policy and BIP-110 signalling, hosting concentration, Lightning nodes. How to run your own node, even on solar power.
- [Bitcoin mining pools: list, share, fees, payouts (2026)](https://21btc.cc/pools): Every major Bitcoin mining pool in one table: live hashrate share, payout scheme (FPPS, PPLNS, solo), fee, Stratum V2 and official site. Plus how to choose a pool.
- [Bitcoin calculator: sats to BTC, USD, EUR, RUB, CNY converter, live](https://21btc.cc/calculator): Sats to BTC and BTC to sats converter: turn satoshis, BTC and mBTC into dollars, euros, rubles and yuan at the live bitcoin price. ECB and Bank of Russia rates.
- [Bitcoin Museum: timeline from the whitepaper to today](https://21btc.cc/museum): Interactive Bitcoin history: whitepaper, genesis block, Pizza Day, halvings, SegWit, Taproot, ETFs. Famous blocks and transactions, Satoshi quotes and early prices, all with sources.
- [Bitcoin is Dead: every time Bitcoin was declared dead, with sources](https://21btc.cc/bitcoin-is-dead): A verified timeline of media and expert claims that Bitcoin is dead, doomed or a scam: date, who said it, the exact quote, source link, archive copy and the BTC price that day versus today. Media history, not a forecast.
- [Bitcoin holders by balance: shrimp to humpback, with sources](https://21btc.cc/bitcoin-holders): Bitcoin addresses by balance: how many hold 1, 10, 100, 1,000 BTC and how coins split from shrimp to humpback. Addresses, not people. Data as of 16 Oct 2026.
- [Bitcoin Law Around the World: regulation by country, with sources](https://21btc.cc/bitcoin-regulation): A sourced guide to the laws that touch Bitcoin directly or indirectly in 42 countries and territories, the EU and offshore centres: legal status, tax, ETFs, state reserves, mining, bans, with a detailed United States section (CLARITY, GENIUS, executive orders, SEC, IRS, FinCEN). Status as of 16 Oct 2026. Not legal advice.
- [Bitcoin Wiki: protocol, mining, people, ETFs and memes explained](https://21btc.cc/wiki): An encyclopedia of Bitcoin in plain words: 150+ interlinked articles on the protocol, mining, Lightning, wallets, people, companies, ETFs, history and memes, with sources and live network data.
- [Early Bitcoiners: cypherpunks, Satoshi and early developers](https://21btc.cc/wiki/people): Who built Bitcoin: sourced profiles of cypherpunks, Satoshi Nakamoto, early developers and Core contributors, with key facts and primary sources.
- [Bitcoin blog: news explained simply, with sources](https://21btc.cc/blog): Short articles on what matters in Bitcoin: protocol debates, security incidents, companies, conferences and history. Every fact is sourced; expectations are labelled.
- [Historic Bitcoin videos: the empty-room talk, Senate hearings, famous explainers](https://21btc.cc/videos): A video hall of 30+ historic Bitcoin videos: Andreas Antonopoulos's 2013 talk to an almost empty room, Senate hearings, Mt. Gox, Buffett's “rat poison squared”, Saylor, El Salvador, 3Blue1Brown. Why each matters, views, date and BTC price then vs now.
- [Bitcoin forum: discuss charts, data and articles](https://21btc.cc/forum): Community discussion for every block on the site: ETF flows, on-chain metrics, network data, guides and articles. Read freely, sign in with X to post.
- [Bitcoin ASIC miners: profitability, prices and issuance by year](https://21btc.cc/shop): Bitcoin ASIC miner catalogue with live profitability, hashprice, break-even, mining pools compared (fees, payout schemes, stratum URLs) and bitcoin issuance by year.
- [Bitcoin for AI: how AI agents pay with Bitcoin (L402, NWC, Cashu, x402)](https://21btc.cc/ai): Why AI agents need Bitcoin, explained with honest caveats: a catalog of agent payment protocols (L402, HTTP 402, Lightning Agent Tools, NWC, Alby MCP, BOLT12, Cashu, Fedimint, Routstr, PPQ.ai, Fewsats, x402) with code, live Lightning data and a card vs Lightning fee calculator.
- [Bitcoin derivatives: open interest, funding rate and liquidations (live)](https://21btc.cc/derivatives): BTC perpetual futures open interest and funding rate on Binance, Bybit, OKX and Deribit, a 30-day history and recent liquidations, from public keyless exchange APIs. Source and time on every block. Not advice.
- [21btc MCP server: read-only Bitcoin data for AI agents (Streamable HTTP)](https://21btc.cc/mcp): A free Model Context Protocol server for Bitcoin data: price, ETF flows, risk, fees, network stats, derivatives, glossary search and events. No keys, read-only tools, 60 requests per minute. Server card included.
- [21btc changelog: what changed on the site, with dates and RSS](https://21btc.cc/changelog): Real shipped changes to 21btc.cc: new pages, data, fixes and speed work, with dates, links and an RSS feed.
- [Bitcoin whitepaper (PDF): Satoshi's 2008 paper, section by section](https://21btc.cc/wiki/bitcoin-whitepaper): Satoshi Nakamoto's 9-page paper of 31 Oct 2008: the PDF link, then all 12 sections in plain words.

## People
- [Bitcoin developers, X influencers and YouTube channels](https://21btc.cc/people): Bitcoin Core maintainers and contributors, Bitcoin-only voices on X and Bitcoin YouTube channels, each verified, with follow buttons.
- [Satoshi Nakamoto: who created Bitcoin, timeline, quotes, coins](https://21btc.cc/wiki/satoshi-nakamoto): The 2008 whitepaper, the genesis block and The Times headline, the first transaction to Hal Finney, verified quotes, the Patoshi estimate of ~1.1M BTC at today's price, the genesis address and identity claims with their status.
- [Michael Saylor: Strategy's bitcoin holdings (live), bio and quotes](https://21btc.cc/wiki/michael-saylor): Strategy (MSTR) bitcoin holdings with average cost and every purchase since 2020, his story, latest posts, verbatim quotes with sources and the stories behind Saylor memes.
- [Randi Hipper: Bitcoin YouTube host of The Daily Zest](https://21btc.cc/wiki/randi-hipper): Randi Hipper (Miss Teen Crypto) hosts The Daily Zest, a daily live Bitcoin and crypto show on YouTube. Her Bitcoin Amsterdam 2026 talks, interviews and links.

## Plan ₿ Forum 2026 speakers (Bitcoin Wiki profiles)
- [Plan ₿ Forum 2026 speakers](https://21btc.cc/wiki/people#planb-2026): 43 speaker profiles from the official Lugano agenda (23–24 Oct 2026): role per the organiser, all sessions with Lugano and London time, official links.
- [Paolo Ardoino](https://21btc.cc/wiki/paolo-ardoino): CEO at Tether. 2 sessions at Plan ₿ Forum 2026.
- [Elizabeth Stark](https://21btc.cc/wiki/elizabeth-stark): CEO & Co-Founder at Lightning Labs. 1 session at Plan ₿ Forum 2026.
- [Adam Back](https://21btc.cc/wiki/adam-back): CEO at Blockstream. 1 session at Plan ₿ Forum 2026.
- [Saifedean Ammous](https://21btc.cc/wiki/saifedean-ammous): Economist, Author and Bitcoin Educator. 2 sessions at Plan ₿ Forum 2026.
- [Roy Sheinfeld](https://21btc.cc/wiki/roy-sheinfeld): CEO at Breez. 3 sessions at Plan ₿ Forum 2026.
- [Samson Mow](https://21btc.cc/wiki/samson-mow): CEO at JAN3. 4 sessions at Plan ₿ Forum 2026.
- [Stephan Livera](https://21btc.cc/wiki/stephan-livera): Bitcoin Podcaster. 5 sessions at Plan ₿ Forum 2026.
- [BTC Sessions](https://21btc.cc/wiki/btc-sessions): Bitcoin Educator/Youtuber. 6 sessions at Plan ₿ Forum 2026.
- [Jimmy Song](https://21btc.cc/wiki/jimmy-song): Bitcoin Educator | Open-Source-Programmer | Author. 4 sessions at Plan ₿ Forum 2026.
- [Joe Nakamoto](https://21btc.cc/wiki/joe-nakamoto): Independent Bitcoin journalist | content creator | MC. 7 sessions at Plan ₿ Forum 2026.
- [Nico Moran](https://21btc.cc/wiki/nico-moran): Host of Simply Bitcoin. 5 sessions at Plan ₿ Forum 2026.
- [Michele Foletti](https://21btc.cc/wiki/michele-foletti): Mayor of City of Lugano. 1 session at Plan ₿ Forum 2026.
- [Mathias Buus](https://21btc.cc/wiki/mathias-buus): CEO at Holepunch. 1 session at Plan ₿ Forum 2026.
- [Giacomo Zucco](https://21btc.cc/wiki/giacomo-zucco): VP Plan B Foundation. 2 sessions at Plan ₿ Forum 2026.
- [Jaromil](https://21btc.cc/wiki/jaromil): Scientific Director, Plan ₿ Foundation. 3 sessions at Plan ₿ Forum 2026.
- [Aaron van Wirdum](https://21btc.cc/wiki/aaron-van-wirdum): OG at Bitcoin Magazine, Author of The Genesis Book. 2 sessions at Plan ₿ Forum 2026.
- [John Carvalho](https://21btc.cc/wiki/john-carvalho): CEO Synonym. 2 sessions at Plan ₿ Forum 2026.
- [Jonas Nick](https://21btc.cc/wiki/jonas-nick): Director of Research at Blockstream. 1 session at Plan ₿ Forum 2026.
- [Robin Linus](https://21btc.cc/wiki/robin-linus): Stanford University. 1 session at Plan ₿ Forum 2026.
- [Mike Schmidt](https://21btc.cc/wiki/mike-schmidt): Executive Director, Brink. 2 sessions at Plan ₿ Forum 2026.
- [Mark Moss](https://21btc.cc/wiki/mark-moss): Host of The Mark Moss Show | Entrepreneur | Investor. 5 sessions at Plan ₿ Forum 2026.
- [Knut Svanholm](https://21btc.cc/wiki/knut-svanholm): Author & Host Bitcoin Infinity Show. 6 sessions at Plan ₿ Forum 2026.
- [Rob Hamilton](https://21btc.cc/wiki/rob-hamilton): Co-Founder AnchorWatch. 2 sessions at Plan ₿ Forum 2026.
- [Kevin Loaec](https://21btc.cc/wiki/kevin-loaec): CEO at Wizardsardine. 2 sessions at Plan ₿ Forum 2026.
- [Rahim Taghizadegan](https://21btc.cc/wiki/rahim-taghizadegan): CEO, deedsats.com. 3 sessions at Plan ₿ Forum 2026.
- [NiftyNei](https://21btc.cc/wiki/niftynei): Founder bitcoin++ & Executive Director Base58 School of Engineering. 3 sessions at Plan ₿ Forum 2026.
- [Rapha Zagury](https://21btc.cc/wiki/rapha-zagury): CEO Twenty One Capital & Founder Elektron. 2 sessions at Plan ₿ Forum 2026.
- [Leon Wankum](https://21btc.cc/wiki/leon-wankum): Real Estate Developer, Author & Philosopher. 2 sessions at Plan ₿ Forum 2026.
- [Hermann Vivier](https://21btc.cc/wiki/hermann-vivier): Founder Bitcoin Ekasi. 1 session at Plan ₿ Forum 2026.
- [Andrew Fenton](https://21btc.cc/wiki/andrew-fenton): Core Contributor. 1 session at Plan ₿ Forum 2026.
- [Pietro Poretti](https://21btc.cc/wiki/pietro-poretti): Head of Economic Development, City of Lugano. 2 sessions at Plan ₿ Forum 2026.
- [Marco Dal Lago](https://21btc.cc/wiki/marco-dal-lago): Chief Expansion Officer, Tether. 1 session at Plan ₿ Forum 2026.
- [Chris Seedor](https://21btc.cc/wiki/chris-seedor): CEO & Co-Founder SEEDOR / bitsurance. 3 sessions at Plan ₿ Forum 2026.
- [Guido Brera](https://21btc.cc/wiki/guido-brera): Founder and President, Be Water. 1 session at Plan ₿ Forum 2026.
- [Silvia Berzoni](https://21btc.cc/wiki/silvia-berzoni): Financial Executive Editor, Chora Media. 2 sessions at Plan ₿ Forum 2026.
- [Arsh Molu](https://21btc.cc/wiki/arsh-molu): Freedom Tech Advocate. 1 session at Plan ₿ Forum 2026.
- [Moritz Kaminski](https://21btc.cc/wiki/moritz-kaminski): Co-Founder at Alby. 1 session at Plan ₿ Forum 2026.
- [Ben Kaufman](https://21btc.cc/wiki/ben-kaufman): Software Developer at Synonym. 2 sessions at Plan ₿ Forum 2026.
- [Dario Varela](https://21btc.cc/wiki/dario-varela): Engineer, Lightning Labs. 1 session at Plan ₿ Forum 2026.
- [Samuel Kullmann](https://21btc.cc/wiki/samuel-kullmann): Member of Parliament, Canton Berne / MA political science. 1 session at Plan ₿ Forum 2026.
- [Marco Argentieri](https://21btc.cc/wiki/marco-argentieri): CEO Ark Labs. 3 sessions at Plan ₿ Forum 2026.
- [Talip](https://21btc.cc/wiki/talip): Research Engineer at LX Research Labs. 1 session at Plan ₿ Forum 2026.
- [Alexandre Laizet](https://21btc.cc/wiki/alexandre-laizet): Board Director at Capital B. 2 sessions at Plan ₿ Forum 2026.

## Bitcoin conferences (upcoming)
- [Bitcoin conferences 2026–2027: dates and cities](https://21btc.cc/events): Bitcoin-only conferences in 2026 and 2027 with dates, cities and links, plus Token2049 and Korea Blockchain Week side events.
- [Plan B Forum Lugano 2026](https://21btc.cc/events/planb-lugano-2026): 23–24 Oct 2026, Lugano, Switzerland. Dates, tickets and details with sources.
- [Bitcoin Amsterdam 2026](https://21btc.cc/events/bitcoin-amsterdam-2026): 5–6 Nov 2026, Amsterdam, Netherlands. Dates, tickets and details with sources.
- [bitcoin++ Seoul 2026](https://21btc.cc/events/btcpp-seoul-2026): 5–6 Nov 2026, Seoul, South Korea. Dates, tickets and details with sources.
- [Bitcoin Korea Conference Seoul 2026](https://21btc.cc/events/bitcoin-korea-2026): 7–8 Nov 2026, Seoul, South Korea. Dates, tickets and details with sources.
- [Bitcoin Histórico San Salvador 2026](https://21btc.cc/events/bitcoin-historico-2026): 11–12 Nov 2026, San Salvador, El Salvador. Dates, tickets and details with sources.

## Tools
- [Free Bitcoin tools and calculators: fees, mining, DCA, charts (live)](https://21btc.cc/tools): Free Bitcoin tools: fee, mining, DCA and what-if calculators, MVRV, rainbow, stock-to-flow, halving countdown. Live data, sources, no sign-up.
- [Bitcoin DCA calculator: what if you bought every month (real prices)](https://21btc.cc/tools/dca-calculator): See what buying the same amount of Bitcoin every week or month would be worth today, on real daily prices since 2010. Year-by-year table, comparison with one purchase. Free, no sign-up.
- [Bitcoin transaction fee calculator: sats and USD by priority](https://21btc.cc/tools/fee-calculator): Estimate a Bitcoin transaction fee from size in vB and live mempool fee rates, for SegWit, Taproot and legacy addresses.
- [Bitcoin halving countdown: blocks left to the 2028 halving](https://21btc.cc/tools/halving-countdown): Live block-height countdown to the next Bitcoin halving, the estimated date from the current block pace, and how the halving works.
- [Bitcoin Fear & Greed Index today: what it is and how to read it](https://21btc.cc/tools/fear-greed): Today's crypto Fear & Greed Index value with history, what goes into it, how to read extreme fear and extreme greed, and its limits. Not investment advice.
- [Bitcoin MVRV ratio and realized price: how to read them](https://21btc.cc/tools/mvrv): Latest MVRV, realized price, and long- and short-term holder MVRV from on-chain data, with a plain explanation of what they measure and their limits.
- [Free Bitcoin halving countdown widget for your site](https://21btc.cc/tools/embed): Copy-paste iframe code for a free, live Bitcoin halving countdown widget. No sign-up, no tracking scripts.

## Video guides (video, transcript, FAQ)
- [What Is Bitcoin? A Simple Explanation for Beginners: video, transcript, FAQ](https://21btc.cc/learn/video/what-is-bitcoin): Who created Bitcoin, how blocks and the blockchain work, the 21 million cap and the halving.
- [What Is the Bitcoin Orange Pill? Explained Simply: video, transcript, FAQ](https://21btc.cc/learn/video/orange-pill): Where the orange pill meme comes from and what it means to orange-pill someone.
- [How to Buy Bitcoin: A Simple Beginner's Guide: video, transcript, FAQ](https://21btc.cc/learn/video/how-to-buy): Ways to buy, starting small in sats, checking fees and moving coins to your own wallet.
- [What Is Bitcoin Mining? Explained Simply: video, transcript, FAQ](https://21btc.cc/learn/video/mining): Blocks, proof of work, difficulty every 2016 blocks, ASICs and the block reward.
- [The Bitcoin Halving Explained: 50 → 3.125 BTC: video, transcript, FAQ](https://21btc.cc/learn/video/halving): Every 210,000 blocks the reward halves: 50 → 25 → 12.5 → 6.25 → 3.125 BTC, toward 21M around 2140.
- [Bitcoin Wallets Explained: Hot vs Cold, Keys and Seed Phrase: video, transcript, FAQ](https://21btc.cc/learn/video/wallets): Hot vs cold wallets, private keys and how to keep a seed phrase safe.
- [Bitcoin Scams to Avoid: Giveaways, Impersonators, Fake Apps: video, transcript, FAQ](https://21btc.cc/learn/video/scams): Fake giveaways, impersonators, fake apps, 'guaranteed returns' and romance scams, plus 3 rules.
- [Bitcoin Fees and the Mempool Explained Simply: video, transcript, FAQ](https://21btc.cc/learn/video/fees-mempool): Why transactions wait in the mempool, fees in sats per vbyte, how miners pick transactions and how to avoid overpaying.
- [What Is a Seed Phrase? Bitcoin Wallet Backup Explained: video, transcript, FAQ](https://21btc.cc/learn/video/seed-phrase): The 12 or 24 words that back up your wallet, and the rules: write it down, never photograph, type or share it.
- [Who Is Satoshi Nakamoto? The Creator of Bitcoin: video, transcript, FAQ](https://21btc.cc/learn/video/satoshi-nakamoto): The 2008 whitepaper, the 2009 genesis block, the first transaction to Hal Finney and why Bitcoin has no leader.
- [What Is a Bitcoin ETF? Explained Simply: video, transcript, FAQ](https://21btc.cc/learn/video/etf): What a spot Bitcoin ETF is, the January 2024 US approval, fund shares vs your own keys, fees and trade-offs. Not investment advice.
- [The Lightning Network Explained Simply: Fast, Cheap Bitcoin Payments: video, transcript, FAQ](https://21btc.cc/learn/video/lightning): A second layer for Bitcoin payments in seconds with tiny fees: payment channels, routing, invoices and wallets.
- [What Is a Blockchain? Blocks Explained Simply: video, transcript, FAQ](https://21btc.cc/learn/video/blockchain): A shared public ledger, a new block about every ten minutes, and hashes that chain blocks so history is very hard to change.
- [Why Are There Only 21 Million Bitcoin?: video, transcript, FAQ](https://21btc.cc/learn/video/21-million): The supply cap in the code, block rewards and halvings, the last fraction around 2140 and 100 million sats per coin. A fixed supply does not guarantee any price.
- [Exchange vs Your Own Wallet: Not Your Keys, Not Your Coins: video, transcript, FAQ](https://21btc.cc/learn/video/exchange-vs-wallet): Exchange balances as IOUs, who holds the keys, lessons of Mt. Gox and FTX, and self-custody with a seed phrase backup.
- [Bitcoin Rainbow Chart Explained: A Meme Model, Not a Forecast: video, transcript, FAQ](https://21btc.cc/learn/video/rainbow-chart): A long-term price chart on a log scale with a logarithmic regression curve and colored bands. A meme that only describes the past, not a forecast. Not investment advice.
- [The Next 1 Billion Bitcoin Users: AI Agents That Pay Without a Bank: video, transcript, FAQ](https://21btc.cc/learn/video/next-billion-users): Why AI agents can't use banks or cards, why Bitcoin asks only for a key, millisats on Lightning and L402 payments inside the web request, plus honest caveats. Not investment advice.
- [How Bitcoin Wallets Get Hacked, and How to Stay Safe: video, transcript, FAQ](https://21btc.cc/learn/video/wallet-hacks): Phishing, seed phrases in the cloud, malware that swaps addresses, fake support, tampered devices, SIM swaps and blind signing, plus four habits that stop most of it.
- [Hardware Wallet Implant & Weak Entropy: What To Do: video, transcript, FAQ](https://21btc.cc/learn/video/hardware-wallet-implant): What Ledger confirmed about the implant in devices sold by CryptoBilis, what is only reported, the Coldcard entropy bug, and four steps: verify firmware, add dice entropy, never type your seed online, buy from the official store. Not investment advice.
- [Your Bitcoin Key Is Only as Safe as Its Randomness (Entropy, Dice): video, transcript, FAQ](https://21btc.cc/learn/video/private-key-randomness): A private key is a very large number picked at random, and people are bad at being random. Where wallets get entropy: system noise, hardware random number chips, your own dice rolls, even radioactive decay. Faulty random number generators and brain wallets made from phrases have led to real thefts. A 12-word seed holds 128 bits of entropy, 24 words hold 256. Not investment advice.
- [Guessing a Bitcoin Key Is the World's Worst Lottery (2^256 Explained): video, transcript, FAQ](https://21btc.cc/learn/video/guess-a-private-key): A key is like 256 coin flips: almost 2^256 possible keys, a number with 78 digits. A computer checking one trillion keys per second for a billion years would cover less than one in 10^48 of them (simple arithmetic). The real risks are bad randomness, phishing, malware and stolen seed phrases, not guessing. Not investment advice.
- [Hot vs Cold Wallet: Where Should Your Keys Live?: video, transcript, FAQ](https://21btc.cc/learn/video/hot-vs-cold-wallet): A hot wallet keeps keys on an internet-connected phone or computer: handy for everyday spending. A cold wallet keeps keys offline, for example on a hardware wallet: better for savings you rarely touch. Many people use both. Not investment advice.

## Bitcointalk classics: guides to the most-read forum threads
- [Bitcoin classics: the most-read bitcointalk threads, explained](https://21btc.cc/learn/bitcointalk-classics): The most-viewed bitcointalk.org threads, from the puzzle transaction to Pizza Day and the block size war, each with a plain-language guide and FAQ.
- [The Bitcoin puzzle transaction: why keys can't be guessed](https://21btc.cc/learn/topics/bitcoin-puzzle): What the famous puzzle addresses are, why small puzzles fall and big ones stay unsolved, and what it tells you about key security.
- [Bitcoin supply and inflation over time](https://21btc.cc/learn/topics/bitcoin-supply-inflation): How the 21 million cap and the halving schedule set Bitcoin's yearly issuance, computed straight from the protocol rules.
- [My Bitcoin transaction is stuck: RBF and CPFP explained](https://21btc.cc/learn/topics/stuck-transaction): Why transactions wait unconfirmed, and the two safe ways to speed them up: replace-by-fee and child-pays-for-parent.
- [Lost wallet password or seed: what can be recovered](https://21btc.cc/learn/topics/lost-wallet-password): What is realistically recoverable when you forget a wallet password or lose a seed phrase, and how to avoid recovery scams.
- [Bitcoin or gold? A plain comparison](https://21btc.cc/learn/topics/bitcoin-vs-gold): How Bitcoin and gold differ on supply, portability, verification, custody and risk, without predictions.
- [Satoshi Nakamoto and Hal Finney: the first Bitcoin transaction](https://21btc.cc/learn/topics/satoshi-and-hal-finney): Who Hal Finney was, how he received the first Bitcoin transaction from Satoshi, and why runners honour him every year.
- [Bitcoin Pizza Day: 10,000 BTC for two pizzas](https://21btc.cc/learn/topics/bitcoin-pizza-day): The story of the first known Bitcoin purchase in May 2010 and what 10,000 BTC is worth at today's price.
- [History of Bitcoin hacks: why 'not your keys, not your coins'](https://21btc.cc/learn/topics/bitcoin-hacks-history): Lessons from the best-known thefts and exchange collapses, from 2011 to FTX, and how self-custody changes the risk.
- [Can you still trust hardware wallets?](https://21btc.cc/learn/topics/hardware-wallet-trust): What the 2026 implant and entropy incidents mean for hardware wallets, and the habits that keep them safe.
- [What a Bitcoin address is: vanity addresses and their risks](https://21btc.cc/learn/topics/vanity-addresses): How addresses come from keys, how vanity generators find addresses with chosen letters, and the scams around them.
- [Bitcoin privacy: UTXOs, address reuse and CoinJoin](https://21btc.cc/learn/topics/bitcoin-privacy): Why Bitcoin is pseudonymous rather than anonymous, and the basic habits that protect your privacy.
- [UTXO consolidation: when fees are low, tidy your wallet](https://21btc.cc/learn/topics/utxo-consolidation): Why many small coins make future payments expensive, and how to merge them when the mempool is quiet.
- [Can Bitcoin make banks disappear? What stops people using it](https://21btc.cc/learn/topics/bitcoin-adoption-barriers): The big-picture debates: what Bitcoin can and can't replace, and the real barriers to everyday use.
- [Can you mine Bitcoin at home? Is it worth it?](https://21btc.cc/learn/topics/mining-at-home): Why laptop mining no longer works, what decides ASIC profitability, and how to check the numbers before you buy.
- [The block size war: who decides Bitcoin's rules](https://21btc.cc/learn/topics/block-size-war): The 2015–2017 fight over bigger blocks, Bitcoin XT, SegWit and the fork, and what it taught about governance.
- [Buying Bitcoin: KYC exchanges vs P2P](https://21btc.cc/learn/topics/kyc-vs-p2p): What KYC/AML means, how peer-to-peer buying works, and the risks of each, with no service recommendations.
- ['How do I multiply my Bitcoin?' The risks explained](https://21btc.cc/learn/topics/grow-bitcoin-risks): Why 'grow your BTC' offers are the most common trap, and how yield, leverage and lending actually work. Not investment advice.
- [El Salvador and Bitcoin as legal tender](https://21btc.cc/learn/topics/el-salvador-legal-tender): What El Salvador's 2021 law did, how it changed in 2025, and what the experiment shows.

## Optional
- [Sitemap](https://21btc.cc/sitemap.xml)
- [Blog RSS](https://21btc.cc/blog/rss.xml)
- [Changelog RSS](https://21btc.cc/changelog/rss.xml)
- [MCP server card](https://21btc.cc/mcp/server-card)
- [Open API for agents](https://21btc.cc/ai/api)