How Bitcoin Works

What Is Bitcoin?

Bitcoin is a cryptocurrency, a digital token first launched in 2009 when an anonymous individual or group going by the user name Satoshi Nakamoto posted a whitepaper on a discussion board.

Bitcoin operates without a financial system or government authorities. It can be used as an alternative to fiat currencies or as an investment, utilizing peer-to-peer transfers on a digital network that records and secures all transactions. This network is powered by a blockchain, an open-source program that chains transaction histories to prevent manipulation.

Learn what's happening behind the scenes in the Bitcoin network to help you further your understanding of this digital phenomenon.

The Bitcoin Blockchain

The Bitcoin blockchain is a database of transactions secured by encryption and validated by peers—here's how it works. The blockchain is not stored in one place; it is distributed across multiple computers and systems within the network. These systems are called nodes. Every node has a copy of the blockchain, and every copy is updated whenever there is a validated change to the blockchain.

The blockchain consists of blocks, which store data about transactions, previous blocks, addresses, and the code that executes the transactions and runs the blockchain. So, to understand the blockchain, it's important first to understand blocks.

Blocks

When a block on the blockchain is opened, the blockchain creates the block hash, a 256-bit number that encodes the following information:

• The current software version: The Bitcoin client version
• The previous block's hash: The hash of the block before the current one
• The coinbase transaction: The first transaction in the block, where the bitcoin reward for opening the block was issued
• The block height number: How far away numerically the block is from the first block
• Merkelroot: A 256-bit number that stores the information about all previous blocks
• Timestamp: The time and date the block was opened
• The target in bits: The network target
• The nonce: A 32-bit number that is added to the block hash

Queued transactions are entered into the block, the block is closed, and the blockchain creates the hash. Each block contains information from the previous blocks, so the blockchain cannot be altered because each block is "chained" to the one before. Blocks are validated and opened by a process called mining.

Bitcoin Mining

Mining is the process of validating transactions and creating a new block on the blockchain. Mining is conducted by software applications that run on computers or machines designed specifically for mining called Application Specific Integrated Circuits.

The hash is the focus of the mining programs and machines. They are working to generate a number that matches the block hash. The programs generate a hash and try to create a number equal to or less than the network target, using the nonce as the variable number. The nonce is increased by a value of one every time a guess is made. The number of hashes a miner can produce per second is its hash rate.

Mining programs across the network generate these hashes, competing to see which one will solve the hash first—the one that does receives the bitcoin reward, a new block is created, and the process repeats for the next group of transactions.

Bitcoin's mining difficulty adjustments will require a longer or shorter string of zeroes, depending on the number of miners on the network. The difficulty is adjusted every 2,016 blocks to hit a rate of about one new block every 10 minutes. The difficulty—or the average number of tries per second to solve the cryptographic puzzle—has been increasing since Bitcoin was introduced, reaching tens of trillions of average attempts to solve the hash.

Mining is intensive, requiring expensive equipment and a lot of electricity to power tit all. There's no telling what nonce will work, so the goal is to plow through them as quickly as possible with as many machines working on the hash as possible to get the reward. This is why mining farms and mining pools were created.

Halving

Halving is an important concept in Bitcoin mining. At first, the mining reward was 50 BTC for solving the hash. About every four years, or 210,000 blocks, the reward is cut in half. So, rewards were cut to 25 in 2012, 12.5 in 2016, and 6.25 in 2020. The last halving occurred on April 19, 2024, reducing the reward to 3.125. The next halving will happen in 2028, further reducing it to 1.5625.

The last bitcoin is expected to be mined somewhere around 2140. All 21 million bitcoins will have been mined at that time, and miners will depend solely on fees to maintain the network.

Bitcoin Keys and Wallets

A common question from those new to Bitcoin is, "I've purchased a bitcoin, now where is it?" The easiest way to understand this is to think about the Bitcoin blockchain as a community bank that stores everyone's funds. You view your balance using Bitcoin wallets, which are like your bank's mobile application.

If you're like many people today, you don't use cash very often and never physically see the money in your checking account. Instead, you use credit and debit cards with security numbers, which act as tools to access and use your money. You access your bitcoin using a wallet and the keys you're given when you receive it.

Keys

A bitcoin, at its core, is a token representing value. The token is digital (or virtual), and your public key is used to assign it to you. Ownership is transferred when transactions are made to another person's public key. You use your wallet, the mobile application, to send or receive bitcoin.

When bitcoin is assigned to an owner via a transaction on the blockchain, that owner receives a number, their private key. Your wallet has a public address—called your public key—that is used when someone sends you a bitcoin, similar to the way they enter your email address in an email.

Wallets

A wallet is a software application used to view your balance and send or receive bitcoin. The wallet interfaces with the blockchain network and locates your bitcoin for you. The blockchain is a ledger with portions of bitcoin stored on it. Because bitcoins are data inputs and outputs, they are scattered all over the blockchain in pieces because they have been used in previous transactions. Your wallet application finds them all, totals the amount, and displays it.

There are two types of Bitcoin wallets: custodial and noncustodial. A custodial wallet is one where a trusted entity, like an exchange, holds your keys for you. For example, when you sign up for a Coinbase exchange account, you can elect to have them store your keys for you as custodians.

Noncustodial wallets are Bitcoin wallets where the user takes responsibility for securing the keys, such as in your wallet application on your mobile phone. Storing keys in an application connected to the internet is called hot storage. Hot storage is the vulnerability most often exploited by hackers and thieves.

To remedy this, the cryptocurrency community has developed methods for storing your keys offline. Most commonly, you'll hear about hot storage, cold storage, and deep cold storage. Hot storage is any wallet that stores your keys and has an active connection to the internet; this is the most vulnerable method. An example of a hot wallet is the wallet application on your mobile device.

Cold storage is any method that is not connected to the internet. This could be a removable USB drive or a piece of paper with your keys written on it (this is called a paper wallet). Deep cold storage is any cold storage method that is secured somewhere that requires additional steps to access the keys beyond removing a USB drive from your desk drawer and plugging it in. Examples might be a personal safe or storage deposit box—anything that takes extra effort to retrieve your keys.

Bitcoin Transactions

A bitcoin transaction occurs when you send or receive a bitcoin. To send a coin, you enter the recipient's address in your wallet application, enter your private key, and agree to the transaction fee. Then, press whichever button corresponds to "send." The receiver must wait for the transaction to be verified by the mining network, which can take some time (occasionally several hours) because transactions wait in a mining queue called the mempool.

The mempool is where transactions waiting to be verified go. The network, on average, confirms a block of transactions about every ten minutes, but not all new transactions go into the new block that is created. This is because blocks only hold a certain amount of information, and each transaction comes with a mining fee.

Transactions must meet the minimum transaction fee threshold to be processed, and the transactions with the highest fees are processed first. This is why you may hear about the problem of rising fees. Bitcoin is so popular that demand for transactions has increased, allowing (or requiring) miners to charge higher fees.

Once the fee is met, the transaction is transferred to a block, where it is processed. Then, the transaction information within the block is validated by miners, the block is closed, and all receivers collect their bitcoin. Both wallets display their appropriate balances, and the next transactions are processed.

Bitcoin Security

The Bitcoin blockchain and network have many parts, but it is not necessary to understand them all to use this new currency technology. You only need to know that you use a wallet to send, receive, and store your Bitcoin keys; you also should use a cold storage method for security because wallets are software, and software can be hacked.

Exchanges that store customers' keys can also be hacked, but many who offer this service take measures to reduce the chances that hackers can get into the storage systems. Most are turning to the enterprise-level cold storage techniques businesses use to store essential data for extended timeframes.

For good reason, many people are concerned about Bitcoin's level of security, especially since it involves exchanging money for encrypted data ownership. However, it's important to note that the Bitcoin blockchain has never been hacked because of the community consensus mechanisms used.

Wallets are the weak spot, so if you're looking to get involved in Bitcoin, it's essential to understand how to utilize cold storage methods and keep your keys out of your hot wallet.

The Bottom Line

Bitcoin is a digital currency that can be used instead of fiat currencies or physical cash. It uses a blockchain to secure transaction information out of the reach of centralized third parties who traditionally facilitate and regulate transactions.

The comments, opinions, and analyses expressed on Investopedia are for informational purposes online. Read our warranty and liability disclaimer for more info. As of the date this article was written, the author does not own bitcoin.