Assuming that i have several utxos in my wallet. Can i know which utxos will be sent when i request a transaction? For example, there are 3 utxos in my wallet: 3 BTC, 5 BTC, 7 BTC. when i send 1 BTC to someone, which utxo will be spent?

  1. biggest one first
  2. oldest one first
  3. smallest one first (but bigger than sending amount)

Of course it depends on the client program, but I'm curious about how it runs in general. (What about bitcoin-core or exchanges?)

  • Bitcoin Core and few other wallets use different coin selection algorithms to select UTXOs which can be used in a transaction. They also provide option to select inputs manually for a transaction.
    – Prayank
    May 3 at 3:11