O que HTML Preview and Validator faz?
HTML Preview and Validator permite inspecionar dados diretamente no navegador e informa com clareza o resultado e os limites. Recursos verificados: Sandboxed HTML preview, Duplicate ID detection, Image alt checks, Form-label checks.
Use local preview for fast feedback, Nu for conformance
This page is suited to safe visual inspection and common structural mistakes. It does not claim complete HTML or accessibility validation.
Como usar?
- Paste an HTML document or fragment.
- Choose Preview for sandboxed rendering or Validate structure for deterministic checks.
- Fix reported document, duplicate-ID, image-alt, or form-label issues and rerun.
Exemplo real de entrada e saída
Find a missing image alternative
Entrada
<main><img src="photo.jpg"><p>Hello</p></main>Saída
Warning: 1 image is missing an alt attribute.The local DOM inspection catches a common accessibility defect without loading a remote validator.
Erros comuns e correções
| Sintoma | Causa provável | Correção |
|---|---|---|
| Scripts do not run in the preview. | The iframe intentionally has a restrictive sandbox. | Use a controlled development environment when script execution is required. |
| No warning appears for a standards issue. | The tool performs focused structural checks, not full conformance validation. | Use the Nu HTML Checker for release-grade standards validation. |
Important behavior of HTML Preview
Limite específico desta ferramenta: These deterministic checks are not a substitute for the complete WHATWG conformance rules or the W3C Nu validator.
Padrões e referências de implementação
- WHATWG HTML Living Standard (opens in a new tab)Defines HTML parsing and document conformance.
- Nu HTML Checker (opens in a new tab)Provides comprehensive standards-oriented HTML checking.
HTML Preview — FAQ
Does the HTML Preview upload my input?
No. Processing runs in the current browser tab, and the page does not send tool input to a KitLumi processing endpoint.
What input does the HTML Preview accept?
It accepts an HTML document or fragment. The workspace checks the input and reports malformed or unsupported values before it produces a result.
What does the HTML Preview produce?
It produces a sandboxed preview and local diagnostics for document, image, ID, and form-label structure. Copy and download controls appear when the output format supports them.
What limitation should I know?
These deterministic checks are not a substitute for the complete WHATWG conformance rules or the W3C Nu validator.
O que mudou?
Atualização material: HTML Preview: Added Sandboxed HTML preview, Duplicate ID detection, Image alt checks, Form-label checks, responsive controls, explicit runtime disclosure, and task-specific examples and limitations.