Catch the obvious HTML source defects before you ship.
Paste your own non-confidential HTML source. The code performs bounded text-only checks inside this browser tab. It does not fetch your URL, submit a form, evaluate pasted scripts, send pasted text to a server, log content, or save it between page loads.
Maximum 128 KiB UTF-8. The checker is a limited heuristic, not a valid HTML parser, renderer, accessibility conformance test or actual website QA report.
Inspection result
Results are observations from the pasted source only. A warning is not proof of a real production defect. Investigate against the actual authorized page.
When you need a real site-level QA handoff
Source-only checks cannot verify HTTP status, redirects, live JavaScript behavior, screen reader interactions, device rendering or a complete customer journey. If you need bounded original testing on up to five publicly accessible pages from one authorized origin, see our separately agreed 19 native Base USDC QA pilot.
Review the 19 USDC paid scope ↗
This link opens a separate truthful quotation page, not a charge. Real buyer approval, written acceptance criteria and lawful payment eligibility are required before commissioned work. No paid customer orders are claimed.
What's checked—and not checked
The heuristic looks for missing document language, title, H1 and description, missing image alt attributes, duplicated IDs, local fragment links without matching IDs, placeholder links, target-blank rel warnings and heading level gaps. Decorative images with an explicitly empty alt attribute are not automatically treated as defects. Comments, script bodies and style bodies are excluded from source markup scanning. Findings are capped in the display, but totals are preserved.
Not checked: semantic accessibility, keyboard interaction, actual rendered DOM, content accuracy, full HTML5 parsing, responsive layouts, security vulnerabilities or production compliance. This example does not load a remote URL and makes no payment or wallet request.
Inspect original publicly readable source and tests: HTML checker core · 18 local test cases.