# Proving Lab

> Measurements on browser tools, OCR pipelines and AI-assisted development.
> Every claim published with method, raw data and a control run. Where our own
> tool performs worse than an alternative, that is stated in the text.

Run by the developer of Full Page PDF Snap, which appears in several of the
measurements. Disclosed on every page where it is relevant.

## Notes

- [Pages that are gone before you need them: eight moments in a degree](https://provinglab.dev/notes/pages-gone-before-you-need-them/): Eight recurring situations in a degree where something on screen becomes evidence later — the submission receipt, a course room that closes, the version of an examination regulation that applied at enrolment, a statistics query that returns different figures next year. With what not to keep: other people's data, and teaching material beyond your own use. German version on the same page.
- [Six things went wrong building software with an AI assistant in one day](https://provinglab.dev/notes/building-with-ai-what-went-wrong/): A logged account of six failures in one working day: a wrong generalisation from Chrome to Firefox (Firefox MV3 uses event pages, not service workers, so an entire rewrite was unnecessary), a factual claim about a competitor that a source check proved false, 22 local filesystem paths staged for a public commit, documentation that contradicted the shipped behaviour, a credential written to the wrong store, and a release that passed every static check and was never executed. Three of six were caught by checking an external source, one by a pointed human question, one by luck, one by nothing.

## Measurements

- [Print to PDF or capture the screen?](https://provinglab.dev/measurements/print-to-pdf-vs-screenshot/): The same Wikipedia article through Firefox's built-in print export and through full-page screenshot capture, 1 August 2026. Print produces 26 pages with 25 breaks, 9 of which cut a sentence in half; capture produces one continuous sheet with none. Print recovers more text (94.8% against 92.7%) because it keeps a real text layer, and its file is six times smaller (1.1 MB against 6.7 MB). Capture wins where layout matters or where an uninterrupted input is needed for OCR or a language model.
- [Webpage to PDF for OCR](https://provinglab.dev/measurements/webpage-to-pdf-for-ocr/): A full-page screenshot PDF run through Tesseract against the source text. 92.6% of the vocabulary recovered, 8/8 critical values correct, 73.9% of five-word phrases verbatim. Recognition collapses below 110 dpi (21.3% real words at 72 dpi); above 150 dpi the gain is 0.3 points for 29% more time.
- [Does your PDF extension upload the page?](https://provinglab.dev/measurements/pdf-extension-permissions/): What eight current PDF extensions declare in their manifests, retrieved 2026-08-01. How to verify permissions in 30 seconds. Server-side converters cannot process pages behind a login — quoted from a provider's own listing.
- [Web citations that vanish: what happens to a source after you cite it](https://provinglab.dev/measurements/web-citations-that-vanish/): 150 web sources from real reference lists, checked: 19.3% are gone, 8.7% have no archived copy anywhere, and where a snapshot exists it is a median of 603 days old. With practical steps for students and a German version. Reference rot and content drift are established in the literature (Klein et al. 2014; Jones et al. 2016 found content had drifted for 76.35% of references; Pew Research Center 2024). The article's own contribution is current archive coverage, plus a documented correction: a first run reported 38.7% gone and 57.3% unarchived because non-answers were counted as negative results.
- [An extension is only as dangerous as its permissions allow](https://provinglab.dev/measurements/extension-permissions-risk/): Why permission scope, not developer reputation, bounds the damage a compromised extension can do. Written one year after Mozilla's documented phishing campaign against add-on developer accounts (2025-08-01).

- [Which page-saving extensions actually run on Firefox for Android?](https://provinglab.dev/measurements/android-capture-extensions/): 248 Firefox extensions for saving or capturing a page, checked against the add-ons API on 2 August 2026. 60 declare Android support, together around 998,000 daily users — SingleFile alone has 85,724. Declaration is not function: a manifest entry permits installation, not working capture, and none were tested on a device. Chrome for Android cannot install extensions at all, which is why it does not appear. Includes the correction of our own store listing, which claimed to be "one of the few".

## Data

- [OCR recall measurement, 2026-08-01](https://provinglab.dev/data/2026-08-01-ocr-recall.json): Raw JSON — recall 92.6 %, five-word phrases 73.9 %, control run 0.0 %, and the full resolution series: 72 dpi 21.3 % real words, 110 dpi 92.7 %, 150 dpi 98.4 %, 220 dpi 98.7 %. CC BY 4.0.
- [Web citation availability, 2026-08-02](https://provinglab.dev/data/2026-08-02-quellen-archiv.json): Raw JSON — per-URL status, verdict, archive timestamp and snapshot age for 150 cited sources. CC BY 4.0.
- [Extension permissions, 2026-08-01](https://provinglab.dev/data/2026-08-01-extension-permissions.json): Raw JSON as retrieved from the Mozilla add-ons API — users, ratings, declared permissions and host permissions for eight extensions.

- [Android-capable capture extensions, 2026-08-02](https://provinglab.dev/data/2026-08-02-android-capture-extensions.json): Raw JSON — 248 extensions retrieved across eight search terms, 60 with an android entry in current_version.compatibility, each with daily users, rating, minimum Android version and AMO URL. CC BY 4.0.

## Tools

- [Full Page PDF Snap](https://provinglab.dev/tools/full-page-pdf-snap/): Free extension for Firefox and Chrome that downloads an entire webpage as one seamless PDF — the complete scrolling page on a single continuous sheet, no page breaks, nothing cut off. Runs entirely on the device, makes no network requests, and asks for activeTab instead of access to all sites. Works on Firefox for Android, where the finished capture opens on a result page with a download button and a share button for passing the PDF to another app. Recurring uses: archiving an invoice or portal message behind a login (a server-side converter cannot reach those), keeping a transaction history that runs over months as one readable sheet for OCR or a language model, and web archiving before a page is edited or removed. A screen-capture PDF is not a qualified electronic document. MIT licensed, source public.
  - Install: [Firefox, desktop and Android](https://addons.mozilla.org/firefox/addon/full_page_pdf_snap_webpagesave/) · [signed file without any store](https://github.com/Bubu89/full-page-pdf-snap/releases/latest) · [Chrome package](https://github.com/Bubu89/full-page-pdf-snap/releases/latest)

## Optional

- [About and disclosure](https://provinglab.dev/about/): Private, non-commercial publication — nothing sold, no advertising, no affiliate links, no tracking. Operated under the pseudonym Silence; full identity disclosed to a legitimate legal requester. States the limits explicitly: nothing here is legal advice, and a screen-capture PDF is not a qualified electronic document.
- [Disclaimer and limitation of liability](https://provinglab.dev/disclaimer/): No warranty for software or content; liability limited as far as the law allows, with intent, gross negligence, injury to life, body or health and mandatory statutory liability expressly unaffected. States that a capture can be incomplete without indicating it, that a screen-capture PDF is not a qualified electronic document, and that nothing published is professional advice.
- [Privacy policy](https://provinglab.dev/privacy.html)
- [Source code](https://github.com/Bubu89/full-page-pdf-snap)