you are only sure when blockchain.info site doesn't show the number of confirmations(I think after 100 confirmations)
But every confirmation makes more and more unlikely some kind of doublespend. At the point of being in practice impossible. After 3 I think the risk is 0 no matter the value.
I'm still to know about some doublespend of a transactions that got 2 or more confirmations.
Topic: How many confirmations to be sure about a transaction? (Read 3657 times)
OP, please close this topic. The question has been answered and all new answer are just copies of the others.
Hi,
1 confirmation for low risk or low btc amount
6 confirmation for high risk high btc amount
Thanks
1 confirmation for low risk or low btc amount
6 confirmation for high risk high btc amount
Thanks
Hi,
1 confirmation for low risk or low btc amount
6 confirmation for high risk high btc amount
Thanks
1 confirmation for low risk or low btc amount
6 confirmation for high risk high btc amount
Thanks
This is a great list 
I bookmarked your post. One question remains. Why 0 confirmations? Wouldn't it be completely risky not waiting until it achieved at least one confirmation?
Nope. In fact, I feel that 0 confirmation is safe for less than $500 as long as it fits a few criteria. I bookmarked your post. One question remains. Why 0 confirmations? Wouldn't it be completely risky not waiting until it achieved at least one confirmation?I think of it like this...
0 confirmations = fast food purchase
3 confirmations = expensive dinner
6 confirmations = cool dirt bike
10 confirmations = 40 acre farm
0 confirmations = fast food purchase
3 confirmations = expensive dinner
6 confirmations = cool dirt bike
10 confirmations = 40 acre farm
1. Inputs must not be unconfirmed
2. Transaction has a reasonable fee/kb
3. There isn't any competing transactions
4. The mining pools and nodes at geographically distributed areas have seen it.
Most mining pools do not accept transactions with spent inputs and would include whichever transaction appeared first. Also, majority of network has Bitcoin Core as their client. They relay which ever transaction came first and would ignore any other transactions with spent input in their mempool. Of course, you can ask a miner to mine the double spend for you but it isn't worth it for less than $500.
maybe 5/6
i'm not sure about it technically but most sites require at least 1 confirmation to use the site and withdraw, some require 3-6 confirmations.
This is a great list I bookmarked your post. One question remains. Why 0 confirmations? Wouldn't it be completely risky not waiting until it achieved at least one confirmation?
I bookmarked your post. One question remains. Why 0 confirmations? Wouldn't it be completely risky not waiting until it achieved at least one confirmation?I think of it like this...
0 confirmations = fast food purchase
3 confirmations = expensive dinner
6 confirmations = cool dirt bike
10 confirmations = 40 acre farm
0 confirmations = fast food purchase
3 confirmations = expensive dinner
6 confirmations = cool dirt bike
10 confirmations = 40 acre farm
6 to be absolutely 100% safe.
I agree. for a lesser value transaction a single confirmation has been safe enough. But like its been said for high value transaction, just to be satisfied regarding the risk of reversing, it is better to go for at least five confirmations.Yes its not really a risk if its like buying a coffee at the starbuck. And one transaction when you are buying something on the internet should not be a big bother if its something like an full priced AAA game.
And the confirmations that "we" recommend to wait before releasing whatever products is not really about the 51% attack. Its more in case we get a rollback because a split or a bug occurred. Some transactions can disappear when that happen, it did in the past, no idea if it will happen again.
Well, the most serious one was with the fork in 2013. The less serious one was with BIP66 but it wasn't a threat unless you use a SPV client. And yeah, you need 30+ confirmations for it to be safe when using SPV client at that time.
6 to be absolutely 100% safe.
I agree. for a lesser value transaction a single confirmation has been safe enough. But like its been said for high value transaction, just to be satisfied regarding the risk of reversing, it is better to go for at least five confirmations.Yes its not really a risk if its like buying a coffee at the starbuck. And one transaction when you are buying something on the internet should not be a big bother if its something like an full priced AAA game.
And the confirmations that "we" recommend to wait before releasing whatever products is not really about the 51% attack. Its more in case we get a rollback because a split or a bug occurred. Some transactions can disappear when that happen, it did in the past, no idea if it will happen again.
6 to be absolutely 100% safe.
I agree. for a lesser value transaction a single confirmation has been safe enough. But like its been said for high value transaction, just to be satisfied regarding the risk of reversing, it is better to go for at least five confirmations.6 to be absolutely 100% safe.
I agree. for a lesser value transaction a single confirmation has been safe enough. But like its been said for high value transaction, just to be satisfied regarding the risk of reversing, it is better to go for at least five confirmations.
Thanks for all the answers. Now I have got a good picture of how many confirmations my transactions need in order to be save.
i would say at least 2 confirmations. But better is to wait until you have 5 confirmations for small amounts. For larger amounts you should wait until at least 20 confirmations.
something between one and six. If in doubt, wait for three confirmations. that's what I would recommend
I have seen alot of people wait between 3-5 transactions so I use that as a rule of thumb for my own transactions.
i think 6 confirmations is enough to get sure about transactions that is 1BTC+.
On other hand 3 confirmations is enough for lower amount of BTCs.
On other hand 3 confirmations is enough for lower amount of BTCs.
Yes these are the best way of getting your bitcoin transaction most securely. But 6confirmation or 3 confirmations are best suited only with latest bitcoin core client only. If you use old bitcoin-qt client then you must wait for some 30 confirmations.
When pools are SPV mining, they don't check the validity of the block and whether it complies with the network. Those mining pools then generate invalid blocks which get invalidated by Bitcoin core 0.10+ but not anything below or on 0.9.4 or earlier as those Core clients are not aware of the new rules. AFAIK, this isn't a threat right now. Majority of pools are mining on correct rules and creating valid blocks.
Which also mean it does not mean if some wallets are outdated and accept some invalid blocks, the network itself will reject it, because most hashrate is pointed at the right wallet version.
Still too bad but not a threat.
A miner generated a block that doesn't follow the rule and miners that verify the blocks do not consider it as valid but those who have SPV mining on will continue mining on that chain and SPV client will follow the longest chain and accept it as valid. This was a threat for merchants accepting 1 confirmation transactions but there wasn't any attack at that time.
i think 6 confirmations is enough to get sure about transactions that is 1BTC+.
On other hand 3 confirmations is enough for lower amount of BTCs.
On other hand 3 confirmations is enough for lower amount of BTCs.
Yes these are the best way of getting your bitcoin transaction most securely. But 6confirmation or 3 confirmations are best suited only with latest bitcoin core client only. If you use old bitcoin-qt client then you must wait for some 30 confirmations.
When pools are SPV mining, they don't check the validity of the block and whether it complies with the network. Those mining pools then generate invalid blocks which get invalidated by Bitcoin core 0.10+ but not anything below or on 0.9.4 or earlier as those Core clients are not aware of the new rules. AFAIK, this isn't a threat right now. Majority of pools are mining on correct rules and creating valid blocks.
Which also mean it does not mean if some wallets are outdated and accept some invalid blocks, the network itself will reject it, because most hashrate is pointed at the right wallet version.
Still too bad but not a threat.
A miner generated a block that doesn't follow the rule and miners that verify the blocks do not consider it as valid but those who have SPV mining on will continue mining on that chain and SPV client will follow the longest chain and accept it as valid. This was a threat for merchants accepting 1 confirmation transactions but there wasn't any attack at that time.
Usually 1 is enough but in the case of confirmations, the more the better!
i think 6 confirmations is enough to get sure about transactions that is 1BTC+.
On other hand 3 confirmations is enough for lower amount of BTCs.
On other hand 3 confirmations is enough for lower amount of BTCs.
Yes these are the best way of getting your bitcoin transaction most securely. But 6confirmation or 3 confirmations are best suited only with latest bitcoin core client only. If you use old bitcoin-qt client then you must wait for some 30 confirmations.
When pools are SPV mining, they don't check the validity of the block and whether it complies with the network. Those mining pools then generate invalid blocks which get invalidated by Bitcoin core 0.10+ but not anything below or on 0.9.4 or earlier as those Core clients are not aware of the new rules. AFAIK, this isn't a threat right now. Majority of pools are mining on correct rules and creating valid blocks.
Which also mean it does not mean if some wallets are outdated and accept some invalid blocks, the network itself will reject it, because most hashrate is pointed at the right wallet version.
Still too bad but not a threat.
I think of it like this...
0 confirmations = fast food purchase
3 confirmations = expensive dinner
6 confirmations = cool dirt bike
10 confirmations = 40 acre farm
0 confirmations = fast food purchase
3 confirmations = expensive dinner
6 confirmations = cool dirt bike
10 confirmations = 40 acre farm
i think 6 confirmations is enough to get sure about transactions that is 1BTC+.
On other hand 3 confirmations is enough for lower amount of BTCs.
On other hand 3 confirmations is enough for lower amount of BTCs.
Yes these are the best way of getting your bitcoin transaction most securely. But 6confirmation or 3 confirmations are best suited only with latest bitcoin core client only. If you use old bitcoin-qt client then you must wait for some 30 confirmations.
When pools are SPV mining, they don't check the validity of the block and whether it complies with the network. Those mining pools then generate invalid blocks which get invalidated by Bitcoin core 0.10+ but not anything below or on 0.9.4 or earlier as those Core clients are not aware of the new rules. AFAIK, this isn't a threat right now. Majority of pools are mining on correct rules and creating valid blocks.
i think 6 confirmations is enough to get sure about transactions that is 1BTC+.
On other hand 3 confirmations is enough for lower amount of BTCs.
On other hand 3 confirmations is enough for lower amount of BTCs.
Yes these are the best way of getting your bitcoin transaction most securely. But 6confirmation or 3 confirmations are best suited only with latest bitcoin core client only. If you use old bitcoin-qt client then you must wait for some 30 confirmations.
i think 6 confirmations is enough to get sure about transactions that is 1BTC+.
On other hand 3 confirmations is enough for lower amount of BTCs.
On other hand 3 confirmations is enough for lower amount of BTCs.
My local exchange coins.ph requires 3 confirmations when cashing out Bitcoin to fiat. So 3 confirmations is sufficient enough.
it really depends on the site if how many confirmation they needed for a transaction to reflect on your balance but atleast 1 confirmation is safe enough and that will not be able to cancel
Most transactions don't really need confirmations to be in the <50% risk range. It only needs a few seconds for it to proporgate around the network and ensure that there isn't any competing transactions. One confirmation would be secure enough to accept the transaction unless there is a block reorg. It would be back to unconfirmed. Most exchanges requires over 3-6 confirmations as losses are not a choice for them with huge trade volumes.
My local exchange coins.ph requires 3 confirmations when cashing out Bitcoin to fiat. So 3 confirmations is sufficient enough.
3 should be very safe, i remember before localbitcoins needed 5 confirmations to confirm the deposit and that was really to much and sometimes took long.
This is what I hate about Kraken. They require 6 confirmations. I don't know why they don't lower this a bit. It takes forever to send your coins to the exchange.
Then again they are very security prone. I guess that's why they still keep 6 confirmations.
3 should be very safe, i remember before localbitcoins needed 5 confirmations to confirm the deposit and that was really to much and sometimes took long.
i think 3+ confirmations is enough to be sure about a transaction ( higher amount ) otherwise if you are transacting low amount then 1+ should be pretty much to be sure with the transaction. 
You can't be 100% certain of a Bitcoin tx until a "checkpoint" has been published (which unfortunately is a centralised thing controlled by the devs).
A blockchain "re-org" (where a better chain replaces the current one) can actually go as far back as the last checkpoint (which could be thousands of blocks).
It is extremely unlikely that such a "re-org" could happen (and has never happened so far) but re-orgs of more than 3 blocks have occurred before (the worst such problem was around 6 blocks from memory).
So you basically have to decide upon the risk you want to take in accordance to the amount you are risking.
A blockchain "re-org" (where a better chain replaces the current one) can actually go as far back as the last checkpoint (which could be thousands of blocks).
It is extremely unlikely that such a "re-org" could happen (and has never happened so far) but re-orgs of more than 3 blocks have occurred before (the worst such problem was around 6 blocks from memory).
So you basically have to decide upon the risk you want to take in accordance to the amount you are risking.
This is why 6 blocks is rock solid. Even 1 block is relatively secure since the odds of anything being redone is low, and also why 3 blocks is standard. Waiting for 6 block is the sweet spot where it does not take *too* long but it is very safe.
Although at this point i am not sure what kind of event that could invalidate 6 blocks old transaction.
You can't be 100% certain of a Bitcoin tx until a "checkpoint" has been published (which unfortunately is a centralised thing controlled by the devs).
A blockchain "re-org" (where a better chain replaces the current one) can actually go as far back as the last checkpoint (which could be thousands of blocks).
It is extremely unlikely that such a "re-org" could happen (and has never happened so far) but re-orgs of more than 3 blocks have occurred before (the worst such problem was around 6 blocks from memory).
So you basically have to decide upon the risk you want to take in accordance to the amount you are risking.
A blockchain "re-org" (where a better chain replaces the current one) can actually go as far back as the last checkpoint (which could be thousands of blocks).
It is extremely unlikely that such a "re-org" could happen (and has never happened so far) but re-orgs of more than 3 blocks have occurred before (the worst such problem was around 6 blocks from memory).
So you basically have to decide upon the risk you want to take in accordance to the amount you are risking.
I think 4 or 5 confirmation before we know and sure the transaction arrive soon in your wallet address.. before i got only 3 confirmation but i didnt recieve it. and its rejected by a blockchain then the bitcoin 4 day or more before the bitcoin came back to a sender...
i believe that you might be safe with one confirmation
When i started to use Bitcoin i had a similar question. Someone told me that 7 confirmation is a must, but better when you wait until it has 20 confirmation as minimum.
above 6, is not needed at all, in most case 3 are sufficient, and in some other case even 1 is okois
usually i do it based on the amount that i'm spending, the more big the more confirmations, up to six
Bitcoin transactions need atleast 3 confirmations by bitcoin network to be fully trusted and confirmed
i believe that you need something like 1 confirmation as people usually cant double spend bitcoins with it
When i started to use Bitcoin i had a similar question. Someone told me that 7 confirmation is a must, but better when you wait until it has 20 confirmation as minimum.
7 is a bit too much. 20 is super overkill. 20 is completely unnecessary in most cases. Of course, there are exceptions like when there was a major fork back in July. But that is easily remedied by keeping your software up to date.
When i started to use Bitcoin i had a similar question. Someone told me that 7 confirmation is a must, but better when you wait until it has 20 confirmation as minimum.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
Many exchanges use 6 confirmations to be sure that it is not a duplicate transaction. However there are other services that only use 3 and other only use 1 confirmation. But to be sure I guess you'll need 6
Even 1 conformation also accepted in some services. It's solely dependent on how much risk you're ready to take. I believe waiting for 3 confirmation are moderate policy for both the parties.
When i buy games or stuff online, it typically go through instantly, but if you end up scamming them, you're the one in trouble since they have your personal information. I understand for anonymous services, waiting for confirmation is an absolute must, however.
In that case, i assume they are dealing with something like Coinbase which i assume cover them in case of a double spending attack?
However the website that i use and give the good immediately, previously obtained my personal information. I guess one way or another they are protected. For instance if its physical product, the transaction will most likely have been confirmed by the time the packaging is ready to be shipped. If its virtual good, like a game on steam, then the code could be perhaps invalidated.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
Many exchanges use 6 confirmations to be sure that it is not a duplicate transaction. However there are other services that only use 3 and other only use 1 confirmation. But to be sure I guess you'll need 6
Even 1 conformation also accepted in some services. It's solely dependent on how much risk you're ready to take. I believe waiting for 3 confirmation are moderate policy for both the parties.
When i buy games or stuff online, it typically go through instantly, but if you end up scamming them, you're the one in trouble since they have your personal information. I understand for anonymous services, waiting for confirmation is an absolute must, however.
It will be 6 confirmations to be 100% sure.
i believe that 2 confirmations might be enough for counting the deposit as it would be really hard to fake something with 2 confirms
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
1 confirmation is usually enough,however if you are dealing with very large numbers id be on the safe side and wait for atleast 3 confirmations. how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
Many exchanges use 6 confirmations to be sure that it is not a duplicate transaction. However there are other services that only use 3 and other only use 1 confirmation. But to be sure I guess you'll need 6
Even 1 conformation also accepted in some services. It's solely dependent on how much risk you're ready to take. I believe waiting for 3 confirmation are moderate policy for both the parties.
When i buy games or stuff online, it typically go through instantly, but if you end up scamming them, you're the one in trouble since they have your personal information. I understand for anonymous services, waiting for confirmation is an absolute must, however.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
Many exchanges use 6 confirmations to be sure that it is not a duplicate transaction. However there are other services that only use 3 and other only use 1 confirmation. But to be sure I guess you'll need 6
Even 1 conformation also accepted in some services. It's solely dependent on how much risk you're ready to take. I believe waiting for 3 confirmation are moderate policy for both the parties.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
Many exchanges use 6 confirmations to be sure that it is not a duplicate transaction. However there are other services that only use 3 and other only use 1 confirmation. But to be sure I guess you'll need 6
I use localbitcoins.com and they require at least 3 confirmations.
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved (reversed)?
Most have been said above. I want to add that 1-2 confirmations is enough under normal network conditions. A few weeks ago, didn't we have a SPV mining issue where a few pools kept mining down the invalid fork? I remember users were advised to raise the bar to 12 confirmations. I would suggest "6" to a newbie just in case.
i think it is enough to get only one transaction as most gambling websites accept deposits with only one confirmation
Actually, most don't. Most gambling sites allow you to start betting with your deposit with 1 confirmation, you can't withdraw your winnings until your deposit has 6 or more confirmations.
As far as I know you don't need even this one confirmation! I bet on sports using NitrogenSports and Directbet and they allow you to place bets with unconfirmed transactions.
It's not like you will run away until your bet (games) don't finish.
i think it is enough to get only one transaction as most gambling websites accept deposits with only one confirmation
Actually, most don't. Most gambling sites allow you to start betting with your deposit with 1 confirmation, you can't withdraw your winnings until your deposit has 6 or more confirmations.
i think it is enough to get only one transaction as most gambling websites accept deposits with only one confirmation
Usually you can trust it with just 1 confirmation. However if you are dealing with people who are acquaintance, counter-partner or dealers, I suggest 8-10 confirmations
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved (reversed)?
Most have been said above. I want to add that 1-2 confirmations is enough under normal network conditions. A few weeks ago, didn't we have a SPV mining issue where a few pools kept mining down the invalid fork? I remember users were advised to raise the bar to 12 confirmations. I would suggest "6" to a newbie just in case.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
3 confirmations is the most common figure that all the escrows of the forum tends to choose.how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
double spending is not possible after that...
there are other forms of attack that can succeed after 3 confirmations and up to evne 5 confirmations, check the weakness of bitcoin
i would wait few conf for small transactions and all the confirmation needed for big transaction
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
I think one transaction should be enough. Mostly bitcoin payment use one transaction to confirm it.how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
But to make sure, six transaction is much better.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
3 confirmations is the most common figure that all the escrows of the forum tends to choose.how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
double spending is not possible after that...
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
3 confirmations is the most common figure that all the escrows of the forum tends to choose.how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
double spending is not possible after that...
Hi i would say...
1 confirmation for low risk or low btc amount eg coffee
6 confirmation for high risk high btc amount eg trading on btc exchanges
Stay safe!
cheers :-)
LondonTrader
1 confirmation for low risk or low btc amount eg coffee
6 confirmation for high risk high btc amount eg trading on btc exchanges
Stay safe!
cheers :-)
LondonTrader
One confirmation is enough for daily transaction and the risk is very low. After six confirmations, the only viable method to reverse a transaction is to execute a 51% attack. You don't need 51% of the network to execute it successfully but with it, you are almost certainly going to succeed. The more the confirmation, the harder it is to reverse. It is not possible to reverse blocks before the last checkpoint.
6 confirmations is super safe, and is also a completely arbitrary number that the core devs came up with several years ago. In reality, you only need 1 confirmation to be relatively safe and 3 for large transactions just to be sure. In most cases, you can accept unconfirmed transactions, although with those, you should check the fee and for any dust outputs just to make sure that it will get confirmed.
Might be good to point out that the wallet itself typically do not let you spend coins before 3 transactions. At least the one i used so far. So it would be a good ballpark as to what is safe.
But in truth, i never had any problem with 1 confirmation, which make it too late to submit another transaction afterwards with a higher fee to create a double spending attack.
I have to agree 6 is the go to if you're talking about a critical amount of money.
6 confirmations is super safe, and is also a completely arbitrary number that the core devs came up with several years ago. In reality, you only need 1 confirmation to be relatively safe and 3 for large transactions just to be sure. In most cases, you can accept unconfirmed transactions, although with those, you should check the fee and for any dust outputs just to make sure that it will get confirmed.
6 is a good heuristic, however 1-2 is relatively safe for low/medium value transactions. The risks decrease exponentially with increased confirmations.
6 to be absolutely 100% safe.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
Like Shorena already touched on explaining, it really depends on what you are trying to buy. For most of the stuff 1 confirmation is enough. If you are buying something really valuable like a real valuable car or you are receiving or buying 100 BTCs for example, then wait for 6 confirmations. More then 6 there is no need whatsoever!
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
I assume you mean reversed, not resolved.
1 confirmation should be fine for most deals. If you do a high value transaction you can reasonably ask for more than one.
Hello,
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
how many confirmations should a Bitcoin transaction have in order to be sure that the transaction could not be resolved?
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