What is Bitcoin?
Bitcoin is a distributed peer-to-peer digital currency that can be transferred instantly and securely between any two people in the world. It's like electronic cash that you can use to pay friends or merchants.

What are bitcoins?
Bitcoins are the unit of currency of the Bitcoin system. A commonly used shorthand for this is “BTC” to refer to a price or amount (e.g. “100 BTC”). There are such things as physical bitcoins, but ultimately, a bitcoin is just a number associated with a Bitcoin Address. A physical bitcoin is simply an object, such as a coin, with the number carefully embedded inside. See also an easy intro to Bitcoin.

How can I get bitcoins?
There are a variety of ways to acquire bitcoins:

  • Accept bitcoins as payment for goods or services.
  • You can buy bitcoins from Bitit Coinbase, Cubits, CoinCorner, BIPS.gif BIPS Market, Circle, or Celery.
  • The most common way to buy bitcoins are the Bitcoin Exchanges
  • There are several services where you can trade them for traditional currency.
  • You can also buy bitcoins using Bitcoin ATMs that are locally in your area.
  • Find someone to trade cash for bitcoins in-person through a local directory.
  • Participate in a mining pool.
  • If you have a lot of mining hardware, you can solo mine and attempt to create a new block (currently yields 25 bitcoins plus transaction fees).
  • Visit sites that provide free samples and offers.

Does Bitcoin guarantee an influx of free money?
Since Bitcoin is a new technology, what it is and how it works may be initially unclear. Bitcoin is sometimes presented as being one of three things:

  • Some sort of online 'get-rich-quick' scam.
  • A loophole in the market economy, the installation of which guarantees a steady influx of cash.
  • A sure investment that will almost certainly yield a profit.
In fact, none of the above are true. Let's look at them independently.

Is Bitcoin a 'get-rich-quick' scheme?
If you've spent much time on the Internet, you've probably seen ads for many 'get-rich-quick' schemes. These ads usually promise huge profits for a small amounts of easy work. Such schemes are usually pyramid/matrix-style schemes that make money from their own employees and offer nothing of any real value. Most convince one to buy packages that will make them earn hundreds a day, which in fact have the buyer distribute more such ads, and make minute profits.

Bitcoin is in no way similar to these schemes. Bitcoin doesn't promise windfall profits. There is no way for the developers to make money from your involvement or to take money from you. That bitcoins are nearly impossible to acquire without the owner's consent represents one of its greatest strengths. Bitcoin is an experimental, virtual currency that may succeed or may fail. None of its developers expect to get rich off of it.

A more detailed answer to this question can be found here.

Will I make money by installing the client?

Most people who use Bitcoin don't earn anything by doing so, and the default client has no built-in way to earn Bitcoins. A small minority of people with dedicated, high-performance hardware do earn some Bitcoins by "mining" (generating new bitcoins, see What is mining?) with special software, but joining Bitcoin shouldn't be construed as being the road to riches. Most Bitcoin users get involved because they find the project conceptually interesting and don't earn anything by doing so. This is also why you won't find much speculation about the political or economic repercussions of Bitcoin anywhere on this site: Bitcoin developers owe their dedication to the project's intellectual yieldings more than to those of a monetary nature. Bitcoin is still taking its first baby steps; it may go on to do great things but right now it only has something to offer those chasing conceptually interesting projects or bleeding edge technology.

As an investment, is Bitcoin a sure thing?

Bitcoin is a new and interesting electronic currency, the value of which is not backed by any single government or organization. Like other currencies, it is worth something partly because people are willing to trade it for goods and services. Its exchange rate fluctuates continuously, and sometimes wildly. It lacks wide acceptance and is vulnerable to manipulation by parties with modest funding. Security incidents such as website and account compromise may trigger major sell-offs. Other fluctuations can build into positive feedback loops and cause much larger exchange rate fluctuations. Anyone who puts money into Bitcoin should understand the risk they are taking and consider it a high-risk currency. Later, as Bitcoin becomes better known and more widely accepted, it may stabilize, but for the time being it is unpredictable. Any investment in Bitcoin should be done carefully and with a clear plan to manage the risk.

Can I buy bitcoins with Paypal?

It is possible to buy physical bitcoins with PayPal but it is otherwise difficult and/or expensive to do so for non-physical bitcoins, because of significant risk to the seller.

While it is possible to find an individual who wishes to sell Bitcoin to you via Paypal, (perhaps via #bitcoin-otc ) most exchanges do not allow funding through PayPal. This is due to repeated cases where someone pays for bitcoins with Paypal, receives their bitcoins, and then fraudulently complains to Paypal that they never received their purchase. PayPal often sides with the fraudulent buyer in this case, which means any seller needs to cover that risk with higher fees or refuse to accept PayPal altogether.

Buying Bitcoins from individuals this way is still possible, but requires the seller to have some trust that the buyer will not file a claim with PayPal to reverse the payment.

Also bitbuy.in allows you to buy Bitcoins with PayPal.

Where can I find a forum to discuss Bitcoin?
Please visit the Community Portal for links to Bitcoin-related forums.

How are new bitcoins created?
New bitcoins are generated by the network through the process of "mining". In a process that is similar to a continuous raffle draw, mining nodes on the network are awarded bitcoins each time they find the solution to a certain mathematical problem (and thereby create a new block). Creating a block is a proof of work with a difficulty that varies with the overall strength of the network. The reward for solving a block is automatically adjusted so that, ideally, every four years of operation of the Bitcoin network, half the amount of bitcoins created in the prior 4 years are created. A maximum of 10,499,889.80231183 bitcoins were created in the first 4 (approx.) years from January 2009 to November 2012. Every four years thereafter this amount halves, so it should be 5,250,000 over years 4-8, 2,625,000 over years 8-12, and so on. Thus the total number of bitcoins in existence can never exceed 20,999,839.77085749 and counting. See Controlled Currency Supply.

Blocks are mined every 10 minutes, on average and for the first four years (210,000 blocks) each block included 50 new bitcoins. As the amount of processing power directed at mining changes, the difficulty of creating new bitcoins changes. This difficulty factor is calculated every 2016 blocks and is based upon the time taken to generate the previous 2016 blocks. See Mining.

What's the current total number of bitcoins in existence?
Current count. Also see Total bitcoins in circulation chart

The number of blocks times the coin value of a block is the number of coins in existence. The coin value of a block is 50 BTC for each of the first 210,000 blocks, 25 BTC for the next 210,000 blocks, then 12.5 BTC, 6.25 BTC and so on.

How divisible are bitcoins?
A bitcoin can be divided down to 8 decimal places. Therefore, 0.00000001 BTC is the smallest amount that can be handled in a transaction. If necessary, the protocol and related software can be modified to handle even smaller amounts.

What do I call the various denominations of bitcoin?
Unlike most currencies, Bitcoin amounts are highly divisible. This has led to a desire to create names for smaller denominations of bitcoin amounts, especially since transactions involving whole bitcoins are no longer quite so common. Bitcoin is decentralized, so there is no organization that can set official names for units. Therefore, there are many different units with varying degrees of popularity. As of 2014, the most common units are bitcoins, bits, and satoshi: 1 bitcoin = 1,000,000.00 bits = 100,000,000 satoshi.

The bitcoin (abbreviated BTC or XBT) is the unit that was used in the original Bitcoin wallet software created by Satoshi Nakamoto. There is nothing particularly special about this unit, but it is by far the most common unit due to tradition.

The smallest value that the Bitcoin network supports sending is the satoshi (sometimes abbreviated sat), one hundred-millionth (0.000 000 01) of a bitcoin. In other words, the network does not support sending fractions of a satoshi. Since it is a hard limit, it seems natural to use it as a unit, though it currently has very little value. The unit was named in honor of Bitcoin's creator after he left -- he was not so vain as to name a unit after himself. The plural of satoshi is satoshi: "Send me 100 satoshi".

Another common unit is the bit, one millionth (0.000,001) of a bitcoin. This unit is the same as a microbitcoin (μBTC). Bits are seen by some as especially logical because they have two-decimal precision like most fiat currencies. You can send 1.23 bits, but not 1.234 bits due to the network's limited precision.

It is also fairly common to use SI prefixes:

  • 0.01 BTC = 1 cBTC = 1 centibitcoin (also referred to as bitcent)
  • 0.001 BTC = 1 mBTC = 1 millibitcoin (also referred to as mbit (pronounced em-bit) or millibit or even bitmill)
  • 0.000,001 BTC = 1 μBTC = 1 microbitcoin (also referred to as ubit (pronounced yu-bit) or microbit)

For an overview of all proposed units of Bitcoin (including less common and niche units), see Units.

How does the halving work when the number gets really small?
Eventually the reward will go from 0.00000001 BTC to zero and no more bitcoins will be created.

The block reward calculation is done as a right bitwise shift of a 64-bit signed integer, which means it is divided by two and rounded down. The integer is equal to the value in BTC * 100,000,000 since internally in the reference client software, all Bitcoin balances and values are stored as unsigned integers.

With an initial block reward of 50 BTC, it will take many 4-year periods for the block reward to reach zero.

How long will it take to generate all the coins?
The last block that will generate coins will be block #6,929,999 which should be generated at or near the year 2140. The total number of coins in circulation will then remain static at 20,999,999.9769 BTC.

Even if the allowed precision is expanded from the current 8 decimals, the total BTC in circulation will always be slightly below 21 million (assuming everything else stays the same). For example, with 16 decimals of precision, the end total would be 20,999,999.999999999496 BTC.

If no more coins are going to be generated, will more blocks be created?
Absolutely! Even before the creation of coins ends, the use of transaction fees will likely make creating new blocks more valuable from the fees than the new coins being created. When coin generation ends, these fees will sustain the ability to use bitcoins and the Bitcoin network. There is no practical limit on the number of blocks that will be mined in the future.

But if no more coins are generated, what happens when Bitcoins are lost? Won't that be a problem?
Because of the law of supply and demand, when fewer bitcoins are available the ones that are left will be in higher demand, and therefore will have a higher value. So, as Bitcoins are lost, the remaining bitcoins will eventually increase in value to compensate. As the value of a bitcoin increases, the number of bitcoins required to purchase an item decreases. This is a deflationary economic model. As the average transaction size reduces, transactions will probably be denominated in sub-units of a bitcoin such as millibitcoins ("Millies") or microbitcoins ("Mikes").

The Bitcoin protocol uses a base unit of one hundred-millionth of a Bitcoin ("a Satoshi"), but unused bits are available in the protocol fields that could be used to denote even smaller subdivisions.

If every transaction is broadcast via the network, does Bitcoin scale?
The Bitcoin protocol allows lightweight clients that can use Bitcoin without downloading the entire transaction history. As traffic grows and this becomes more critical, implementations of the concept will be developed. Full network nodes will at some point become a more specialized service.

With some modifications to the software, full Bitcoin nodes could easily keep up with both VISA and MasterCard combined, using only fairly modest hardware (a single high end server by todays standards). It is worth noting that the MasterCard network is structured somewhat like Bitcoin itself - as a peer to peer broadcast network.

Frequently Asked Questions about Bitcoin

How does Bitcoin work?

From a user perspective, Bitcoin is nothing more than a mobile app or computer program that provides a personal Bitcoin wallet and enables a user to send and receive bitcoins.

Behind the scenes, the Bitcoin network is sharing a massive public ledger called the "block chain". This ledger contains every transaction ever processed which enables a user's computer to verify the validity of each transaction. The authenticity of each transaction is protected by digital signatures corresponding to the sending addresses therefore allowing all users to have full control over sending bitcoins.

Thus, there is no fraud, no chargebacks and no identifying information that could be compromised resulting in identity theft. To learn more about Bitcoin, you can consult the original Bitcoin whitepaper, read through the extremely thorough Frequently Asked Questions, listen to a Bitcoin podcast or read the latest Bitcoin news.

How does one acquire bitcoins?

As payment for goods or services. Purchase bitcoins at a Bitcoin exchange. Exchange bitcoins with someone near you. Earn bitcoins through competitive mining. While it may be possible to find individuals who wish to sell bitcoins in exchange for a credit card or PayPal payment, most exchanges do not allow funding via these payment methods. This is due to cases where someone buys bitcoins with PayPal, and then reverses their half of the transaction. This is commonly referred to as a chargeback.

Is Bitcoin legal?

To the best of our knowledge, Bitcoin has not been made illegal by legislation in most jurisdictions. However, some jurisdictions (such as Argentina and Russia) severely restrict or ban foreign currencies. Other jurisdictions (such as Thailand) may limit the licensing of certain entities such as Bitcoin exchanges.

Regulators from various jurisdictions are taking steps to provide individuals and businesses with rules on how to integrate this new technology with the formal, regulated financial system. For example, the Financial Crimes Enforcement Network (FinCEN), a bureau in the United States Treasury Department, issued non-binding guidance on how it characterizes certain activities involving virtual currencies.

Can Bitcoin be regulated?

The Bitcoin protocol itself cannot be modified without the cooperation of nearly all its users, who choose what software they use. Attempting to assign special rights to a local authority in the rules of the global Bitcoin network is not a practical possibility. Any rich organization could choose to invest in mining hardware to control half of the computing power of the network and become able to block or reverse recent transactions. However, there is no guarantee that they could retain this power since this requires to invest as much than all other miners in the world.

It is however possible to regulate the use of Bitcoin in a similar way to any other instrument. Just like the dollar, Bitcoin can be used for a wide variety of purposes, some of which can be considered legitimate or not as per each jurisdiction's laws. In this regard, Bitcoin is no different than any other tool or resource and can be subjected to different regulations in each country. Bitcoin use could also be made difficult by restrictive regulations, in which case it is hard to determine what percentage of users would keep using the technology. A government that chooses to ban Bitcoin would prevent domestic businesses and markets from developing, shifting innovation to other countries. The challenge for regulators, as always, is to develop efficient solutions while not impairing the growth of new emerging markets and businesses.