Input and Output

Definition

In UTXO-based blockchains, inputs reference previous transaction outputs being spent, while outputs define new recipients and amounts. Transactions consume inputs and create outputs—the difference between input and output sums becomes the transaction fee.

Technical Explanation

Each input contains: previous transaction ID, output index, and proof of authorization (signature). Each output contains: amount and spending conditions (recipient's public key hash). Outputs are either spent (referenced as inputs) or unspent (UTXOs available for future spending).

Transactions must satisfy: total inputs ≥ total outputs, valid authorization for each input, and correct structure. The UTXO model provides parallelizable validation, simpler double-spend prevention, and natural privacy (no account balances visible).

SynX Relevance

SynX uses a UTXO model with privacy enhancements. Ring signatures obscure which inputs are actually spent; RingCT hides output amounts. The fundamental input/output structure remains, but privacy features make transaction graph analysis infeasible.

Frequently Asked Questions

Why do transactions have multiple inputs?: Combining UTXOs when their total exceeds the payment amount. Like using multiple bills to pay.
What's change output?: When inputs exceed the payment, the difference returns to you as a new output.
Can I see input/output amounts in SynX?: Only your own transactions—privacy features hide amounts from external observers.

Private transactions, proven structure. Experience SynX