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Font Size Detector

Calibrate with a known reference or run live page analysis to get pixel-perfect typographic scale for developers and designers.

design Privacy-first • Client-side

Upload image / PDF

Drop your image here or click to upload

Supports JPG, PNG, WebP, GIF, PDF • Max 10MB (25MB for PDF)

✓ Runs locally in your browser — nothing uploaded

Or paste HTML/CSS directly — works for private pages.

Results will appear here

This is the extensible result shell. Future AI/API integration will populate:

  • Match + confidence %
  • Family, weight, style, category
  • License / source (free, Google, Adobe)
  • Live preview with your text
  • Similar / alternative fonts
  • Next actions: download, buy, test, copy CSS
Inter — Regular 400 92% match
FREE • Google Fonts Sans Serif

Architecture ready for pluggable AI providers — UI not coupled to a single API. Swap provider via env.

How it works

1

Provide reference

Upload image with known height or set scale.

2

Measure

We compute cap-height → font size mapping.

3

Export

Copy CSS with fluid scale.

Image ruler + calibration
Live DOM metrics
px/rem/pt output
Copy CSS

FAQ

Accuracy?

Within ~5% from high-res images; exact from live DOM.

Need a different tool?

Browse all 12 detectors or search guides.

Privacy note

Heavy image/PDF processing stays in your browser when possible. No fonts or files stored.