SumatraPDF

What it does

SumatraPDF is a small, fast, open-source Windows reader for PDF, EPUB, MOBI, comic archives, DjVu, XPS, CHM and images, with a portable build that runs from a USB stick without installation. It is primarily a viewer, but supports annotations, highlights, stamps and image insertion, certificate-based digital signing, and from pre-release 3.7 a set of command-line tools for merging, compressing, converting, extracting and AES-256 password encryption. There is no cloud service, no OCR and no redaction.

Best for: Windows users who want a very fast, ad-free reader for large or unusual documents, and who are comfortable with a command line for occasional PDF surgery.

Worth knowing: Windows only, with no OCR. The more advanced modification tools — merge, compress, encrypt and redaction — are documented for the 3.7 pre-release rather than the current stable build, so a stable-reader user should not expect them automatically. Redaction there is vendor-documented applied removal and has not been independently tested. macOS, Linux and Android are explicitly ruled out by the developers.

Details, and where each comes from

Vendor statements, our own reading of their pages, and the things nobody has established yet, each answered separately. Where we have not confirmed something it says so rather than guessing, and a row nobody has established is greyed out.

Versions covered

Windows

Website

sumatrapdfreader.org

Requires an account

No

Watermark on the free tier

No

Maximum file size

Not verified

Batch processing

Not verified

Data residency

Self-hosted

Open source

Yes

Self-hostable

Yes

Licence

GPLv3

Redaction

Not determined

Programmatic access

None

Last availability check

Responded in 486 ms 16 October 2026

Checked automatically by our own runner, not reported by the vendor. 100% of our last 30 checks got a response.

What the vendor says

Claims are labelled rather than repeated as fact. Where we have checked something ourselves, it says so and shows when. Checked means we read the vendor's own page and it says what we recorded — not that we tested the behaviour, unless the note says we did.

• “Free and open source — no ads, no bundled software, no subscription”

  Checked by us — the source says this Read 22 September 2026

  Confirmed verbatim: the line appears unaltered on the page, and the page's own FAQ repeats the substance independently — "Yes. Sumatra PDF is completely free and open source, with no ads or bundled software." Three of the four parts of the claim are therefore asserted twice on the same page, and the fourth, "no subscription", is implicit in a free product rather than stated. The page's framing is a comparison with commercial readers — "does everything a closed-source and/or commercial product does, but better in every way" — which is the vendor's assessment rather than a checkable claim. Recorded as the project's description; no control was run.

  Standing: Re-read: the text is unchanged, but the page publishes values that move

  Check it yourself: the source, the SHA-256, and how we checked

  Read

  https://www.sumatrapdfreader.org/free-pdf-reader

  From

  the text a browser renders

  SHA-256

  61d999e1450ecee7c72917bdea8d60418f50955b127cfd67ae6be0d92892ee09

  How we checked: Re-verified verbatim on 2026-09-22: https://www.sumatrapdfreader.org/free-pdf-reader re-rendered in headless Chrome with scripts/render-page.mjs and the claim's wording found in the rendered text. Originally verified on 2026-09-21. sourceHash is the SHA-256 of the re-rendered text, held as rv-www-sumatrapdfreader-org-free-pdf-reader-8c5e51ef.txt.

  What this hash proves, and what it does not

Each claim is quoted from the vendor's own pages. This section describes what we have and have not checked — it is not a judgement about anyone.