Specifying fee amount using bitcoinjs I'm currently playing with bitcoinjs (https://bitcoinjs.org/) and I'm creating offline transactions that I broadcast over the network after.

I've successfully create my first transaction using this : https://medium.com/@orweinberger/how-to-create-a-raw-transaction-using-bitcoinjs-lib-1347a502a3a

But it seems my transaction is stuck since I haven't put enough fee on it to get it mined.

How using a var tx = new bitcoin.TransactionBuilder(); can I set the fee to a certain amount ? Is this calculated using a default value ?

Thank you for your help !
The fee is the sum of unspent value in a Transaction.

Aka the value NOT SENT by your outputs.


  fee = in - out


For an example,  if we assume the input aa94ab02c182214f090e99a0d57021caffd0f195a81c24602b1028b130b63e31, 0 has an unspent value of 15000...

var txb = new bitcoin.TransactionBuilder()
txb.addInput('aa94ab02c182214f090e99a0d57021caffd0f195a81c24602b1028b130b63e31', 0)
txb.addOutput('1Gokm82v6DmtwKEB8AiVhm82hyFSsEvBDK', 15000)


When we send 15000 to 1Gokm82v6DmtwKEB8AiVhm82hyFSsEvBDK, the fee is the value of the inputs minus the value of outputs.


  in:15000 - out:15000 = fee:0


For a fee to be non-zero, in > out is required.