Facet: a diamond listing decoder

A quiet diamond-shopping companion. On any listing, anywhere: how big the stone really is in millimeters (the number carat weight hides), a one-click scan of the page for the carat and shape, a reusable comparison brief, and the grading labs' own verification pages.

Facet is usable now in sixteen forms:

1. The public calculator at https://jacobiusmakes.github.io/facet-diamond-tool/.
2. An installable web app offered directly by the calculator on supported browsers.
3. A zero-install bookmarklet, available on that page, that scans the visible listing locally.
4. A browser extension, available from GitHub Releases while store review is pending.
5. A true-size printable comparison sheet with a 50 mm calibration check and a QR return path.
6. A downloadable diamond shortlist workbook with one attributable Facet link per candidate.
7. Same Stone, a local-only duplicate listing detector for report and measurement matches across sellers.
8. Stone on Hand, a credit-card-calibrated diamond footprint preview that keeps the hand photo on-device.
9. A drop-in web component that publishers and developers can install with one script tag.
10. Report Lens, a local-only text-layer PDF reader for IGI, GIA, and GCAL grading reports.
11. An operating-system share target that reduces explicitly shared listing text to shape and carat before the Facet page opens.
12. Link Mint, a scriptless publisher-link and local QR generator for newsletters, documents, print, and platforms that remove scripts.
13. Stone Card, a local shareable PNG with a size estimate and measurable Facet return QR.
14. A citation-ready open size dataset in CSV and JSON, with 84 reproducible rows under CC BY 4.0.
15. Spread Check, a local grading-report dimension comparison that reports a numeric plan-area difference without inventing a cut grade.
16. The Diamond Size Atlas, 84 open-license SVG diagrams with an image sitemap and attributable return path.

The extension never names or targets a competitor, never sends page text, and never tracks in the background. It runs only when clicked (activeTab) and stores nothing. The bookmarklet sends the calculator only a detected shape and carat weight, never the page URL, seller, or report number. Every Stienhardt click carries utm_source=facet plus shape and carat intent, so visits and orders can be attributed without collecting browsing history.

Same Stone stores seller, URL, price, report, measurements, and notes only in the shopper's browser. Its capture bookmarklet passes page text directly between browser tabs, parses it locally, and does not upload or retain the captured text. Exact certificate matches and possible measurement matches remain separate. Inventory clicks use same_stone_duplicate_match or same_stone_candidate_match and carry only shape and carat intent.

Stone on Hand uses the 85.60 mm long edge of an ISO ID-1 payment card to translate photo pixels into an approximate physical scale. The hand photo is decoded and rendered on an in-browser canvas, then discarded when the tab closes. Direct and shared-preview inventory clicks remain separate as hand_preview_match and hand_preview_shared_match.

The public tool can also create a shareable shape-and-carat check for a shopper's partner. The print sheet returns through via=print, and its Stienhardt clicks use utm_content=print_chart_match. The shortlist workbook returns through via=sheet, and its Stienhardt clicks use utm_content=shortlist_sheet_match without sending the candidate's seller, listing URL, price, report number, or notes. A compact iframe and a drop-in web component are documented in EMBED.md for publishers that want to place the tool in an article. The component is also available from jsDelivr using the repository release tag. Shared briefs and each publisher slug remain separate in utm_content.

Report Lens reads a text-layer PDF with a bundled copy of Mozilla PDF.js. The PDF, extracted text, and report number stay in the browser. The inventory route carries only report_lens_match, shape, and carat. A report-based request to Jacob uses report_lens_intent plus a random FC-... code in the shopper's email. The report number is deliberately excluded from the prefilled message.

On supported installed-PWA platforms, Facet is registered as a POST share target. The service worker extracts the shape and carat from explicitly shared text and strips the listing URL before redirecting to the calculator. Inventory clicks use share_target_match. The paste fallback uses pasted_listing_match and performs the same extraction in the page.

The full source registry, permitted intent fields, prohibited analytics fields, and permanent surface names are in attribution-registry.json. Machine-readable discovery is available through llms.txt, tools.json, and robots.txt. These describe each public utility and its privacy boundary without requiring a crawler to infer behavior from marketing copy.

The open size dataset publishes the same approximate model as 84 rows spanning 1.0 to 3.0 carats in 0.1 carat increments. CSV and JSON downloads are licensed under CC BY 4.0, and CITATION.cff gives GitHub and research tools a machine-readable citation. Each row returns to Facet through via=data; a later inventory click uses dataset_reference.

Spread Check accepts the exact length and width from a grading report and compares their product with the model's expected length-width product for the same shape and carat. The coefficient for a given outline cancels in the comparison, so the result is stated as a plan-area proxy difference. It is not a cut grade, light-performance grade, or quality verdict. Inventory clicks use spread_check_match.

The Diamond Size Atlas converts the open dataset into 84 reusable SVG diagrams. Each asset names its shape, carat weight, approximate millimeter dimensions, model limitation, source, and CC BY 4.0 license. image-sitemap.xml exposes the collection to image crawlers. An atlas row returns through via=atlas; a later inventory click uses size_atlas_reference. Reuse terms and the required credit line are in ATLAS-LICENSE.txt.

Link Mint creates a publisher-specific Facet link from a public publication slug, supported shape, and carat weight. It can download a QR PNG without sending the link to a QR service. Stone Card creates a portrait PNG for partner or group-chat sharing. Its QR returns through share_card_match, then preserves the supported shape and carat in any deliberate inventory visit or coded email request.

Publisher web component

<script src="https://cdn.jsdelivr.net/gh/JacobiusMakes/facet-diamond-tool@v0.4.1/facet-widget.js"></script>
<facet-diamond-size publisher="your-publication" shape="oval" carat="1.50"></facet-diamond-size>

The component has isolated styles, no runtime dependency, and no background tracking. It accepts publisher, shape, carat, and theme="dark" attributes. Inventory clicks use utm_content=web_component_<publisher> plus normalized shape and carat intent.

The same tagged release is also available as an ES module through https://esm.sh/gh/JacobiusMakes/facet-diamond-tool@v0.4.1/facet-widget.js and as a standalone file or npm-ready package archive from GitHub Releases.

WordPress

Install facet-diamond-size-wordpress-0.2.0.zip from the WordPress release, then place this in any post, page, or Shortcode block:

[facet_diamond_size publisher="your-publication" shape="oval" carat="1.50" commerce="off"]

If publisher is omitted, the plugin derives a public attribution slug from the site's hostname. The directory-safe build bundles its script and has no external link by default. A site owner can set commerce="on" to add the attributed inventory route deliberately. Download: https://github.com/JacobiusMakes/facet-diamond-tool/releases/tag/wordpress-v0.2.0

Same math and data as diamond-mcp (facts.json anchors: round 6.5, oval 8.0x5.5, emerald 7.0x5.0, Dutch Marquise 9.4x5.1 at 1 carat, the last scaled from a certified reference stone; cube-root scaling), same honesty note.

Load the extension locally

1. chrome://extensions, turn on Developer mode, "Load unpacked", pick this folder.
2. Open any diamond listing, click the Facet icon, "Scan this page".

Browser store submission

• Upload the matching store-specific release ZIP at the Chrome Web Store, Edge Add-ons, or Firefox Add-ons dashboard, category Shopping, single purpose: "shows diamond face-up size and lab verification links". Privacy: no data collected. Justify activeTab + scripting: user-initiated page scan.
• Store listing copy is in LISTING.md. Each package records Chrome, Edge, Firefox, or direct GitHub distribution separately in its commerce links and email intent source. The Firefox build includes the required add-on ID and an explicit none data-collection declaration.

Test

npm test

The tool intentionally supports only shapes with vetted one-carat anchors: round, oval, emerald, and Dutch Marquise. More shapes belong only after their anchors are reviewed.

New and materially updated public pages are submitted through IndexNow using the repository's path-scoped verification key. IndexNow acceptance means the update was received, not that a search engine promises to crawl or rank it.

PDF extraction uses Mozilla PDF.js 6.3.289 under the Apache License 2.0. The vendored license is at vendor/pdfjs/LICENSE.pdfjs.

Link Mint QR generation uses qrcode-generator 2.0.4 by Kazuhiko Arase under the MIT License. It is bundled locally so a generated publisher link is never sent to a QR service. The vendored license is at vendor/qrcode/LICENSE.qrcode.