Question: What is the longest a transaction can stay unconfirmed for?

[spindoc]

As title, i have a transaction un-confirmed since 14/12/2017. I would have thought it should have dropped from the mempools by now?
Thanks in advance for any input you might have

[BitMaxz]

Base on what i experienced before when sending bitcoin to other wallet it takes 6 days for me before its rejected and i can send bitcoin again but should need to increase the fee in order to cover  my old unconfirmed transaction with low fee... its work for me when sending a bitcoin again with enough fee just to include the parent transaction to the child transaction..

If your transaction still unconfirmed and still not rejected by mempool you can try some transaction accelerator that i think it can help you to accelerate and push your transaction to the network.. 
You can try to accelerate it in antpool check this thread https://bitcointalk.org/index.php?topic=1951859.0
But i don't think if this is still working or not.
The other accelerator from viabtc check it here https://pool.viabtc.com/tools/txaccelerator/
There are 2 option to choose paid or free if you wanted to more faster confirmation you can use paid but you can try free. .

If its rejected and you can able to send again you can try this method

Hi, I saw you posted on my thread regarding help for Bitcoin tx acceleration.
In your tx I noticed that you have made the transaction to your own address itself.

To confirm it in the next block instantly do this :
1. Create a new address say X
2. Send 0.0001BTC to that new address X from your address on which BTC is stuck I.e 1Fh2GwdSfSDpfB5PpYjscB9u2inCoTmumX and this time include a fee of 850satoshi per byte on the transaction.

Your stuck tx will get confirmed in the next block if you follow this.

Note the bitcoin address above is just an example use your bitcoin address..  this method works to me when my transaction takes 6 days and rejected in electrum and send it again with the enough fee that  you can found here https://bitcoinfees.earn.com/
Please use the fastest default fee so that you transaction can be confirm sooner..

[NeuroticFish]

From what I've read (sources: this and this) the latest additions change the max from 72h to 14 days(!) until a tx is dropped from the mempool.

Also if your wallet or somebody may have re-broadcasted your tx, in a hope to accelerate it. (some "accelerators" seem to only re-broadcast, nothing else).

[MintDice]

Usually 3 days is the most. That is not very common.

[spindoc]

Base on what i experienced before when sending bitcoin to other wallet it takes 6 days for me before its rejected and i can send bitcoin again but should need to increase the fee in order to cover  my old unconfirmed transaction with low fee... its work for me when sending a bitcoin again with enough fee just to include the parent transaction to the child transaction..

If your transaction still unconfirmed and still not rejected by mempool you can try some transaction accelerator that i think it can help you to accelerate and push your transaction to the network.. 
You can try to accelerate it in antpool check this thread https://bitcointalk.org/index.php?topic=1951859.0
But i don't think if this is still working or not.
The other accelerator from viabtc check it here https://pool.viabtc.com/tools/txaccelerator/
There are 2 option to choose paid or free if you wanted to more faster confirmation you can use paid but you can try free. .

If its rejected and you can able to send again you can try this method

Hi, I saw you posted on my thread regarding help for Bitcoin tx acceleration.
In your tx I noticed that you have made the transaction to your own address itself.

To confirm it in the next block instantly do this :
1. Create a new address say X
2. Send 0.0001BTC to that new address X from your address on which BTC is stuck I.e 1Fh2GwdSfSDpfB5PpYjscB9u2inCoTmumX and this time include a fee of 850satoshi per byte on the transaction.

Your stuck tx will get confirmed in the next block if you follow this.

Note the bitcoin address above is just an example use your bitcoin address..  this method works to me when my transaction takes 6 days and rejected in electrum and send it again with the enough fee that  you can found here https://bitcoinfees.earn.com/
Please use the fastest default fee so that you transaction can be confirm sooner..

Thanks for chipping in, my main problem with your suggestions is that i did not send the transaction but it's funny you should mention earn.com because that is where the tx is from. I have also contacted them to see if there wallet is constantly broadcasting the transaction but they wont give a clear answer.

[spindoc]

From what I've read (sources: this and this) the latest additions change the max from 72h to 14 days(!) until a tx is dropped from the mempool.

Also if your wallet or somebody may have re-broadcasted your tx, in a hope to accelerate it. (some "accelerators" seem to only re-broadcast, nothing else).

So if the tx is being broadcast constantly with the low fees it was sent at, it could technically stay unconfirmed forever?

[exstasie]

As title, i have a transaction un-confirmed since 14/12/2017. I would have thought it should have dropped from the mempools by now?
Thanks in advance for any input you might have

With most default settings, yes. The problem is that it can be re-broadcasted. If someone (like a Bitcoin Cash supporter) wanted to play up the perception of congestion and high fees on the Bitcoin network, they could continually re-broadcast all unconfirmed low-fee transactions. A script can do this trivially. I believe this is why people are commonly having low-fee transactions stuck for weeks at a time now.

From what I've read (sources: this and this) the latest additions change the max from 72h to 14 days(!) until a tx is dropped from the mempool.

Also if your wallet or somebody may have re-broadcasted your tx, in a hope to accelerate it. (some "accelerators" seem to only re-broadcast, nothing else).

So if the tx is being broadcast constantly with the low fees it was sent at, it could technically stay unconfirmed forever?

Yes. As long as the transaction is valid, anybody can just keep broadcasting it. There are tools like doublespend.py that can easily double-spend low fee transactions. You could also import the keys into another wallet and re-spend the inputs.

[Thirdspace]

So if the tx is being broadcast constantly with the low fees it was sent at, it could technically stay unconfirmed forever?

if you use bitcoin core, abandon transaction to stop broadcasting, and re-create tx with higher fee then broadcast it again
if you have problem with broadcasting, get its signed hex rawtx and push it to some nodes
for eg. go to blockexplorer.com and check your old tx, if it doesn't exist or dropped, push your new tx thru this node
pushing your new tx on a node still having your old tx in its mempool will resulted auto reject pushtx

[spindoc]

Thanks everybody for the input, i have another question: if a transaction is view-able on blockchain.info but not on blockexplorer.com does that mean the Tx is valid or not?

[olim]

Thanks everybody for the input, i have another question: if a transaction is view-able on blockchain.info but not on blockexplorer.com does that mean the Tx is valid or not?

You wouldn't see it on blockchain.info if the transaction was invalid.

Most likely you don't see it on blockexplorer.com because it has been rejected (squeezed out) from their node(s) mempool, probably due to congestion.

What is the "fee per byte" shown on blockchain.info?

[spindoc]

Thanks everybody for the input, i have another question: if a transaction is view-able on blockchain.info but not on blockexplorer.com does that mean the Tx is valid or not?

You wouldn't see it on blockchain.info if the transaction was invalid.

Most likely you don't see it on blockexplorer.com because it has been rejected (squeezed out) from their node(s) mempool, probably due to congestion.

What is the "fee per byte" shown on blockchain.info?

Fee per byte   8.407 sat/B
Sent from earn.com(formerly 21.co) lol