ViewKit vs ValidateHTML

A side-by-side comparison built from both listings. Blank cells mean the company has not given that detail; we never guess.

ViewKit compared with ValidateHTML
Detail	ViewKit	ValidateHTML
What it does	Free in-browser viewer for scientific and ML data files	HTML validation API and free online validator for deployed pages
Stage	Not given	Not given
Founded	Not given	Not given
Based in	Not given	FR
Pricing model	Not given	Freemium
Pricing	Free	Free: unlimited validators and checkers, no account required, free site scans. Solo: 49 EUR per month including full site reports and monitoring of 1 site. Agency: 149 EUR per month including monitoring of 10 sites. Automatic fixes: from 3 EUR for 10 pages, 1 free fix daily without account. Full sit
Key features	Browse HDF5 groups, datasets and attributes Read Parquet schemas, row groups and column statistics Open Zarr v2 and v3 stores from a folder or a zip Inspect Apache Arrow and Feather files View CSV, TSV and Excel spreadsheets Load NumPy .npy and .npz arrays List safetensors tensors and step through TFRecord records Slice N-dimensional arrays and render heatmaps Parse every file locally, with no upload Work offline after page loads	Accessibility (WCAG) validation with machine-detectable failures HTML specification compliance checking Meta tags and viewport validation Open Graph checker Page weight measurement and compression analysis Single API endpoint with configurable checks Single verdict field for build pipeline integration Automatic AI-powered HTML fixes Weekly site audits with change notifications GitHub Actions integration
What makes it different	All data processing happens in your browser with no server uploads Opens very large files by reading only the bytes you view No installation, account or login required Comprehensive articles explaining data format specifications	One API call runs five checks on a single page fetch instead of five separate requests Single boolean verdict for build pipelines to act on without parsing prose False-positive filtering eliminates unreliable findings Quality score based on issue variety, not count, capping best-practice impact Free tools remain unlimited without account or daily limits
Free plan	Not given	Not given
Open source	Not given	Not given
Platforms	Not given	Not given
Public API	Not given	Not given
Community votes	0	0
DR (Domain Rating by Ahrefs)	Not checked yet no change since last check	9 no change since last check
Trust Flow (Majestic)	0	10
Citation Flow (Majestic)	22	32
Referring domains (Majestic)	20	124

4 details filled in for both companies.

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