validator

A validator is an entity or component that checks whether a subject complies with defined rules, standards, or constraints. Validators exist in many domains, from software development to distributed systems and governance, and they play a key role in ensuring correctness, integrity, and trust.

In software and data processing, validators verify user input, data fields, or messages against type constraints, ranges, formats, and inter-field relationships. They may sanitize input to remove harmful data, reject invalid submissions, and provide informative error feedback. Validation can occur on the client side, server side, or during data exchange, and is often complemented by normalization and authentication.

In blockchain and distributed ledgers, a validator (also called a consensus validator) is a node authorized to validate transactions and sometimes to propose new blocks. Validators participate in consensus protocols, verify digital signatures and rules, and receive rewards or staking incentives. The role and requirements for validators vary by protocol; some systems use proof-of-work miners, while others rely on proof-of-stake or other consensus mechanisms.

Validators also appear in standards and security contexts, such as validating XML or JSON documents against schemas and validating digital certificates along a trust chain. In these cases, validators ensure data structure, compatibility, and trustworthiness, enabling reliable interoperability and secure communications.

Design and maintenance considerations for validators include correctness, performance, determinism, and security. Well-designed validators enforce consistent rules, minimize false positives and negatives, and are tested with representative input. They are a foundational element of reliable software, data quality, and secure networks.