Quote from: wsxdrfv on February 21, 2018, 02:47:15 PM

Quote from: Colorblind on February 21, 2018, 02:36:50 PM

Quote from: wsxdrfv on February 21, 2018, 08:34:50 AM

From bitcoin newest source, how can I set transaction fee as more lower?

Some wallet(ledger nano hardware wallet) even provide now custom transaction fee, how is possible?

In Bitcoin you are the one who decides what fee you want to pay. All fees are optional (i.e you can pay 0 fee), however fee is something that rises the chances of your transaction to get into block (higher the fee - faster you can expect it to confirm). If you fee is too low - your transaction may never be confirmed since miners usually pick transactions with higher fees to include in block first. Usually fee is calculated depending on the size of your transaction message (in bytes). You can uread more on fees here https://support.earn.com/digital-currency/bitcoin-transactions-and-fees/how-do-i-calculate-my-transaction-fee

I mean, as programmer, need to know the source about fee and make control of fee's default value for normal user.

Optimal fees are a function of the current state of the mempool, which means it is hard to code it into the static code as a pre-fixed value. This used to happen previously (e.g. 0.0001 BTC fee) but no more at least on advanced wallets. You need to know how urgent your transaction is, and set your fee accordingly.