Sumcheck

PDF & documents → Markdown, checked

100% on-device · no uploads, ever

Install from the Chrome Web Store View source on GitHub Privacy policy

What it does

Sumcheck is a Chrome extension that converts documents into clean Markdown, HTML, plain text or structured JSON — without sending them anywhere. PDFs (including scans, read with on-device OCR), Word, Excel, PowerPoint, EPUB, images, web pages, and a dozen more formats. Everything runs inside your browser: no accounts, no per-page charges, no telemetry, zero network requests at runtime.

Every format it converts

The complete list, straight from the converter's own registry. Anything here can be dropped onto Sumcheck and comes back as Markdown, HTML, plain text or structured JSON.

Documents — .pdf (born-digital and scanned, read with on-device OCR), .docx, .docm, .dotx, .odt, .rtf
Spreadsheets — .xlsx, .xlsm, .xltx, .ods, .csv, .tsv, .psv
Presentations — .pptx, .pptm, .potx, .odp
Ebooks & web — .epub, .html, .htm, .xhtml, and saved web pages (.mhtml, .mht)
Email — .eml
Images, read with the same on-device OCR — .png, .jpg, .jpeg, .gif, .bmp, .webp, .tif, .tiff
Data & text — .json, .jsonl, .ndjson, .yaml, .yml, .xml, Jupyter notebooks (.ipynb), .md, .markdown, .txt, .log
Subtitles — .srt, .vtt
Archives — drop a .zip and it converts what is inside

Sumcheck also converts the browser tab you are looking at, or just the text you have highlighted — no file needed.

It tells you what it is unsure about

Most converters hand you text and leave you to trust it. Scanned documents are where that gets expensive: a $ misread as a 3 turns $40.00 into 340.00, and the result looks perfectly reasonable.

Sumcheck checks its own work and marks what it cannot vouch for:

currency columns where one amount lost its $
line items that do not add up to the stated total
a prominent total that matches nothing else on the page
words that are not words — a confident inchided for "included"
regions of a page OCR could not read at all

Every flag is written where a reader will see it. Nothing is ever silently rewritten.

Open, and open about its limits

Sumcheck is open source under the Apache License 2.0, and its conversion quality is measured against a ground-truth corpus of real scanned documents rather than asserted. The "no network requests" claim is a property of the code, not a promise — read the source or inspect the package.