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Bitcoin Basic

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:

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:
  1. Some sort of online 'get-rich-quick' scam.
  2. A loophole in the market economy, the installation of which guarantees a steady influx of cash.
  3. 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.

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.
Further discussion on this topic can be found on the forums here:

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.
Learn more about Scalability.

Economy

Where does the value of Bitcoin stem from? What backs up Bitcoin?

Bitcoins have value because they are useful and because they are scarce. As they are accepted by more merchants, their value will stabilize. See the list of Bitcoin-accepting sites.
When we say that a currency is backed up by gold, we mean that there's a promise in place that you can exchange the currency for gold. Bitcoins, like dollars and euros, are not backed up by anything except the variety of merchants that accept them.
It's a common misconception that Bitcoins gain their value from the cost of electricity required to generate them. Cost doesn't equal value – hiring 1,000 men to shovel a big hole in the ground may be costly, but not valuable. Also, even though scarcity is a critical requirement for a useful currency, it alone doesn't make anything valuable. For example, your fingerprints are scarce, but that doesn't mean they have any exchange value.
Alternatively it needs to be added that while the law of supply and demand applies it does not guarantee value of Bitcoins in the future. If confidence in Bitcoins is lost then it will not matter that the supply can no longer be increased, the demand will fall off with all holders trying to get rid of their coins. An example of this can be seen in cases of state currencies, in cases when the state in question dissolves and so no new supply of the currency is available (the central authority managing the supply is gone), however the demand for the currency falls sharply because confidence in its purchasing power disappears. Of-course Bitcoins do not have such central authority managing the supply of the coins, but it does not prevent confidence from eroding due to other situations that are not necessarily predictable.

Is Bitcoin a bubble?

Yes, in the same way as the euro and dollar are. They only have value in exchange and have no inherent value. If everyone suddenly stopped accepting your dollars, euros or bitcoins, the "bubble" would burst and their value would drop to zero. But that is unlikely to happen: even in Somalia, where the government collapsed 20 years ago, Somali shillings are still accepted as payment.

Is Bitcoin a Ponzi scheme?

In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.
A ponzi scheme is a zero sum game. Early adopters can only profit at the expense of late adopters. Bitcoin has possible win-win outcomes. Early adopters profit from the rise in value. Late adopters, and indeed, society as a whole, benefit from the usefulness of a stable, fast, inexpensive, and widely accepted p2p currency.
The fact that early adopters benefit more doesn't alone make anything a Ponzi scheme. All good investments in successful companies have this quality.

Doesn't Bitcoin unfairly benefit early adopters?

Early adopters in Bitcoin are taking a risk and invested resources in an unproven technology. By so doing, they help Bitcoin become what it is now and what it will be in the future (hopefully, a ubiquitous decentralized digital currency). It is only fair they will reap the benefits of their successful investment.
In any case, any bitcoin generated will probably change hands dozens of time as a medium of exchange, so the profit made from the initial distribution will be insignificant compared to the total commerce enabled by Bitcoin. Many of the earliest users of Bitcoin have traded their coins at valuations below $1 US, or other amounts which are small compared to contemporary prices.

Won't loss of wallets and the finite amount of Bitcoins create excessive deflation, destroying Bitcoin?

Worries about Bitcoin being destroyed by deflation are not entirely unfounded. Unlike most currencies, which experience inflation as their founding institutions create more and more units, Bitcoin will likely experience gradual deflation with the passage of time. Bitcoin is unique in that only a small amount of units will ever be produced (twenty-one million to be exact), this number has been known since the project's inception, and the units are created at a predictable rate.
Also, Bitcoin users are faced with a danger that doesn't threaten users of any other currency: if a Bitcoin user loses his wallet, his money is gone forever, unless he finds it again. And not just to him; it's gone completely out of circulation, rendered utterly inaccessible to anyone. As people will lose their wallets, the total number of Bitcoins will slowly decrease.
Therefore, Bitcoin seems to be faced with a unique problem. Whereas most currencies inflate over time, Bitcoin will mostly likely do just the opposite. Time will see the irretrievable loss of an ever-increasing number of Bitcoins. An already small number will be permanently whittled down further and further. And as there become fewer and fewer Bitcoins, the laws of supply and demand suggest that their value will probably continually rise.
Thus Bitcoin is bound to once again stray into mysterious territory, because no one exactly knows what happens to a currency that grows continually more valuable. Many economists claim that a low level of inflation is a good thing for a currency, but nobody is quite sure about what might happens to one that continually deflates. Although deflation could hardly be called a rare phenomenon, steady, constant deflation is unheard of. There may be a lot of speculation, but no one has any hard data to back up their claims.
That being said, there is a mechanism in place to combat the obvious consequences. Extreme deflation would render most currencies highly impractical: if a single Canadian dollar could suddenly buy the holder a car, how would one go about buying bread or candy? Even pennies would fetch more than a person could carry. Bitcoin, however, offers a simple and stylish solution: infinite divisibility. Bitcoins can be divided up and trade into as small of pieces as one wants, so no matter how valuable Bitcoins become, one can trade them in practical quantities.
In fact, infinite divisibility should allow Bitcoins to function in cases of extreme wallet loss. Even if, in the far future, so many people have lost their wallets that only a single Bitcoin, or a fraction of one, remains, Bitcoin should continue to function just fine. No one can claim to be sure what is going to happen, but deflation may prove to present a smaller threat than many expect.
For more information, see the Deflationary spiral page.

What if someone bought up all the existing Bitcoins?

Bitcoin markets are competitive -- meaning the price of a bitcoin will rise or fall depending on supply and demand at certain price levels. Only a fraction of bitcoins issued to date are found on the exchange markets for sale. So even though technically, a buyer with lots of money could buy all the bitcoins offered for sale, unless those holding the rest of the bitcoins offer them for sale as well, even the wealthiest, most determined buyer can't get at them.
Additionally, new currency continues to be issued daily and will continue to do so for decades; though over time the rate at which they are issued declines to insignificant levels. Those who are mining aren't obligated to sell their bitcoins so not all bitcoins will make it to the markets even.
This situation doesn't suggest, however, that the markets aren't vulnerable to price manipulation. It doesn't take significant amounts of money to move the market price up or down, and thus Bitcoin remains a volatile asset.

What if someone creates a new block chain, or a new digital currency that renders Bitcoin obsolete?

That the block chain cannot be easily forked represents one of the central security mechanisms of Bitcoin. Given the choice between two block chains, a Bitcoin miner always chooses the longer one - that is to say, the one with the more complex hash. Thusly, it ensures that each user can only spend their bitcoins once, and that no user gets ripped off.
As a consequence of the block chain structure, there may at any time be many different sub-branches, and the possibility always exists of a transaction being over-written by the longest branch, if it has been recorded in a shorter one. The older a transaction is though, the lower its chances of being over-written, and the higher of becoming permanent. Although the block chain prevents one from spending more Bitcoins than one has, it means that transactions can be accidentally nullified.
A new block chain would leave the network vulnerable to double-spend attacks. However, the creation of a viable new chain presents considerable difficulty, and the possibility does not present much of a risk.
Bitcoin will always choose the longer Block Chain and determines the relative length of two branches by the complexities of their hashes. Since the hash of each new block is made from that of the block preceding it, to create a block with a more complex hash, one must be prepared to do more computation than has been done by the entire Bitcoin network from the fork point up to the newest of the blocks one is trying to supersede. Needless to say, such an undertaking would require a very large amount of processing power and since Bitcoin is continually growing and expanding, it will likely only require more with the passage of time.
A much more distinct and real threat to the Bitcoin use is the development of other, superior virtual currencies, which could supplant Bitcoin and render it obsolete and valueless.
A great deal of careful thought and ingenuity has gone into the development of Bitcoin, but it is the first of its breed, a prototype, and vulnerable to more highly-evolved competitors. At present, any threatening rivals have yet to rear their heads; Bitcoin remains the first and foremost private virtual currency, but we can offer no guarantees that it will retain that position. It would certainly be in keeping with internet history for a similar system built from the same principles to supersede and cast Bitcoin into obsolescence, after time had revealed its major shortcomings. Friendster and Myspace suffered similar fates at the hand of Facebook, Napster was ousted by Limeware, Bearshare and torrent applications, and Skype has all but crushed the last few disciples of the Microsoft Messenger army.
This may sound rather foreboding, so bear in mind that the introduction of new and possibly better virtual currencies will not necessarily herald Bitcoin's demise. If Bitcoin establishes itself sufficiently firmly before the inception of the next generation of private, online currencies so as to gain widespread acceptance and general stability, future currencies may pose little threat even if they can claim superior design. This is known as the network effect.

Is Bitcoin open to value manipulation?

The current low market cap of Bitcoin means that any investor with deep enough pockets can significantly change/manipulate the rate. Is this a problem?
This is only a problem if you are investing in Bitcoin for short period of time. A manipulator can't change the fundamentals, and over a period of 5-10 years, the fundamentals will win over any short term manipulations.