Frequently asked questions¶

What is a "safe PDF"?¶

A PDF that Dangerzone rebuilt from pictures of each page of the original. It contains only those pictures and, if you enabled OCR, a text layer. That removes any script, embedded files or logic that was present in the original document. See How Dangerzone works.

Can Dangerzone tell me whether a file is malicious?¶

No. Unfortunately, Dangerzone can't tell you if a file is safe. It just creates a copy that is.

What is OCR, and why does Dangerzone ask for a language?¶

OCR stands for "Optical Character Recognition": software that reads the text in a picture. Dangerzone uses it to add an invisible text layer, which makes the documents searchable and copy-pastable. OCR works much better when it knows which language to expect, hence the language choice.

Does Dangerzone remove watermarks and tracking information?¶

It depends on where the information lives.

• Metadata (author, software, file creation dates, camera model, GPS coordinates, editing history) is removed as part of the process.
• Hidden document structure (comments, embedded files, scripts, links) is also removed.
• Anything visible on the page will not be removed. For example, visible watermarks, printer tracking dots, unusual spacing, unique wording, or steganography hidden in the image will not be removed. If you are a source, treat this as a separate risk that Dangerzone does not address. See When should I use Dangerzone?.

Is there a command-line version?¶

Yes. dangerzone-cli is installed next to the graphical application on every platform, and can convert files from the terminal. See Convert documents from the command line and the dangerzone-cli reference.

Why not just open PDFs in Firefox, which has its own sandbox?¶

Browser viewers such as PDF.js render the PDF inside the browser's sandbox, which does contain many attacks. Two differences remain. First, the PDF is still the original file: once you save or forward it, the next person gets every script and link it carried. Second, browser sandboxes are a target in their own right and escapes are found regularly. Dangerzone gives you a new file that is safe in any viewer, produced in a sandbox that runs nothing else and has no network.

Isn't this overkill for everyday use?¶

For files you trust, yes. Dangerzone is aimed at people who regularly open files from strangers, such as journalists, lawyers and researchers (or anyone handling one specific suspicious file, really). Converting takes seconds for a short PDF and the result is heavier and less editable than the original. Use it when you feel a file is suspicious, and see When should I use Dangerzone? for the cases where it isn't the right tool.

Why would I convert a JPG or PNG? They are just pictures.¶

Image formats are decoded by complex libraries, and those libraries have had serious vulnerabilities in the past. Exploits delivered through crafted images, including PNG and SVG files, have been used in the wild. Dangerzone decodes the image inside the sandbox and re-encodes only the pixels. It also strips image metadata, such as camera model and GPS coordinates, which is often what people want when sharing a picture.

Why is the safe PDF so large?¶

Every page is stored as an image. Dangerzone compresses the result, but a picture of a page of text is still larger than the text itself. Long documents with OCR take the longest and produce the biggest files.

Has Dangerzone received a security audit?¶

Yes, Dangerzone received its first security audit by Include Security in December 2023. The audit was generally favorable: it didn't identify any high-risk findings, only 3 low-risk and 7 informational ones.

Can I run Dangerzone in an airgapped environment?¶

Yes, Dangerzone is designed to run in airgapped environments without any configuration. If you want to update its container image, follow our instructions.

Can I use a custom runtime, such as Podman Desktop?¶

On Windows and macOS, Dangerzone embeds Podman, so there is no need to.

To use a different podman version, such as Podman Desktop, follow our documentation.

I'm experiencing an issue while using Dangerzone¶

First, make sure you use the latest version of Dangerzone.

If the problem persists, please report it.

Why does Dangerzone need to download something on first start?¶

The sandbox is a container image of a few hundred megabytes. On macOS and Windows it is bundled in the installer. On Linux, the slim dangerzone package downloads it on first use so that the package itself stays small and the sandbox can be updated independently. The dangerzone-full package bundles it instead. See Independent sandbox updates.

Which platforms and document formats are supported?¶

See Supported platforms and Supported document formats.

Where can I report security issues?¶

Please check our security policy for preferred communication methods, and for what's in scope for security issues.

How can I become involved?¶

We welcome contributors to the project, regardless of their level of expertise. We don't have a place where we hang out at the moment, but you can reach out to us either via a GitHub issue or support <at> dangerzone.rocks!

If you are a programmer, feel free to pick up an issue labelled good first issue and set up a development environment.