Each output is considered as Unspent Transaction Output (UTXO) until an input consumes it.
UTXO is an unspent transaction output that can be spent as an input to a new transaction.
A Complete Guide to Understanding This Blockchain Concept
Transaction input data structure is shown in the following table: Field Size Description Transaction hash 32 bytes This is the hash of the previous transaction with UTXO.
Output index 4 bytes This is the previous transactions output index, that is, UTXO to be spent.
In the preceding example the inputs are defined under “inputs” : [ section.
Inputs Generally, each input spends a previous output. Each output is considered as Unspent Transaction Output (UTXO) until an input consumes it. UTXO is an unspent transaction output that can be spent as an input to a new transaction. Transaction input data structure is shown in the following table: Field Size Description Transaction hash 32 bytes This is the hash of the previous transaction with UTXO. Output index 4 bytes This is the previous transactions output index, that is, UTXO to be spent. 1-9 Script length This is the size of the unlocking script. bytes Unlocking script Variable Input script (ScriptSig) which satisfies the requirements of the locking script. Sequence Usually disabled or contains lock time. Disabled is represented by 4 bytes number ‘0xFFFFFFFF’. In the preceding example the inputs are defined under “inputs” : [ section.
Why This Matters for Blockchain Technology
Understanding Inputs is not just an academic exercise — it has real-world implications for how blockchain systems are designed, deployed, and secured. Whether you are a developer building decentralized applications, a business leader evaluating blockchain adoption, or a curious learner exploring the technology, this knowledge provides a critical foundation.
Key Points to Remember
- Each output is considered as Unspent Transaction Output (UTXO) until an input consumes it.
- UTXO is an unspent transaction output that can be spent as an input to a new transaction.
- Transaction input data structure is shown in the following table: Field Size Description Transaction hash 32 bytes This is the hash of the previous transaction with UTXO.
- Output index 4 bytes This is the previous transactions output index, that is, UTXO to be spent.
Conclusion
Inputs represents one of the many innovative layers that make blockchain technology so powerful and transformative. As distributed systems continue to evolve, a solid understanding of these core concepts becomes increasingly valuable — not just for developers, but for anyone building, investing in, or working alongside blockchain-powered systems.
Whether you are just starting your blockchain journey or deepening existing expertise, mastering these fundamentals gives you the tools to think clearly about decentralized systems and make smarter decisions in this rapidly evolving space.