isSemantic.net vs VitalSentinel Schema Validator

isSemantic.net is a free web tool for validating, generating, visualizing and converting structured data. Its validator accepts JSON-LD, RDFa and Microdata and checks them against Schema.org, Google Search, Facebook Open Graph, Twitter Cards, Facebook App Links and HTML outline semantics. Markup using other vocabularies appears separately and is not validated. The generator creates or edits examples for Google Search, Schema.org, Open Graph and Twitter Cards, accepts imported snippets and allows added Schema.org properties. Google and Schema.org output is JSON-LD; Open Graph and Twitter Cards output is RDFa. The RDF visualizer shows a graph, triples table and hierarchy. It supports formats including JSON-LD, Microdata, N-Quads, N-Triples, N3, RDFa, RDF/XML, TriG and Turtle, with provisional RDF-star support. The converter accepts a URL or snippet, detects formats and converts serializations. Terms restrict use to private, non-commercial purposes.

VitalSentinel Schema Validator checks structured data on a page URL and separates missing, recommended and broken information. It examines JSON-LD blocks individually, including nested entities and entities within an @graph. For broken blocks, it identifies line and column and names common causes such as trailing commas, curly quotes and HTML entities. Its property checks distinguish Google-required from recommended fields for Article, Product, FAQPage, Recipe, Event, BreadcrumbList, LocalBusiness and Organization; other listed types are not graded. It also flags non-absolute image URLs, dates outside ISO format and prices containing a currency symbol. The free checker reads server-sent HTML, so it cannot see JSON-LD inserted by JavaScript. It reports microdata and RDFa when present but does not grade them. A valid result does not guarantee a Google rich result, and the tool recommends Google's Rich Results Test for rendered pages and eligibility checks. It is available on web and via API. The plan list includes a free plan and Starter at $39 a month.