How to Stop Your Online Course Materials From Being Shared

Where course materials leak

Courses usually have two kinds of content: the lessons (mostly video) and the files that go with them: PDF workbooks, templates, slide decks, checklists, image packs. The files are the easy part to copy and re-share, in places like:

• Private groups and communities where a student posts "here's the whole workbook."
• Free-download and file-sharing sites that collect paid material.
• Resale of your course or its bonuses by someone who bought one seat.
• Shared logins or links passed around inside a team or a friend group.

Most sharing is careless rather than malicious, but a single leak can undercut every future sale.

What the usual protections can and can't do

Common defenses help, but each has a gap:

• A password or login on the member area stops outsiders, not the student who is already inside.
• Download limits and expiring links slow things down, but a file that was downloaded once can be re-shared forever.
• A visible watermark with the student's name or email deters sharing, but it can be cropped, covered or removed, and some creators don't like putting students' personal data on every page.
• Metadata (author, custom properties) is lost when someone re-saves the file, prints to PDF or takes a screenshot.

None of these tells you who shared a file once it's out in the open. For a longer comparison, read visible vs invisible watermarks.

The approach: one invisibly marked copy per student

An invisible forensic watermark is a pattern written into the pixels of an image or PDF that nobody notices at normal viewing size. If every student receives a copy with a different pattern, each file carries a label pointing to that copy, even after it has been renamed. A re-upload, a resize, or a screenshot can still match when enough of the mark survives.

It doesn't stop anyone from sharing. It gives you evidence, and if students know the files are traceable, most think twice.

How to set it up

1. Decide what to mark. Mark the files that carry the value: the main workbook, the templates exported as PDF, the slide deck exported as PDF, and the images that come with the course. Marking everything is better than marking one file.
2. Create one copy per student, or per group. With Markedfile you upload the file and create a copy for each recipient. Use a neutral label such as an order number, not a name.
3. Deliver each student their own copy. If your platform lets you attach a file per purchase, use that. If it only serves one file to everyone, you can send the personalized copies by email, or deliver them in batches (for example one copy per cohort).
4. Keep the record outside the file. Note which label belongs to which order or cohort.
5. If a file leaks, check it. Download what you found, upload it to Detect, and see which copy it matches.

Files are processed in memory and are not stored. The Free plan covers 5 active files with detection for 6 months, and paid plans start at $9.99/month. If you sell at scale, the Business and Enterprise plans include an API so you can mark files from your own system, including video (POST /api/v1/mark and /api/v1/detect, up to 10 min and 100 MB, MP4 download); see the docs.

What to do after a match

A match tells you which copy a file came from. It doesn't prove who posted it: the student may have shared a link, a friend may have used their laptop, or an account may have been compromised. Treat it as a starting point.

• Contact the student first, politely, with where you found the file.
• State it in your terms. Say that materials are individually marked and may not be shared. Telling students up front is what makes the mark a deterrent.
• Pause access to the member area or future bonuses if your terms allow it.
• Request a takedown from the site hosting the file if you own the rights.

Where this approach has limits

• Video is on the Business and Enterprise plans. On those plans, Markedfile also marks video: up to 10 minutes and 100 MB per video, downloaded as MP4. A marked video can still be traced after it's re-encoded, trimmed or downscaled to 720p, even with metadata stripped, thanks to the invisible frame pattern (up to about 85% confidence from the pattern alone; about 99% when the signed metadata is kept too). A screenshot of a frame is checked as an image and is weaker evidence. Don't expect it after heavy compression or sizes below 480p, and never as 100%. Other plans don't include video. Audio and live streams aren't covered.
• Detection is never guaranteed. Strong editing, heavy compression or a very small crop can destroy a mark. Images and video frames under 96×96 px are rejected; everything else uses the same pattern. A crop of roughly 256 px of a detailed area is the approximate minimum, not a ceiling. A resize can still miss on a heavily textured image. Images marked before the latest resize improvement need to be marked again. Older patterns are not detected, so those files have to be marked again.
• PDFs: The PDF mark is now invisible, and PDFs marked before this change aren't compatible, so re-mark them. A screenshot can be checked if it shows roughly 200 pt of a ticket, 160 pt of a photo, 320 pt of a slide, or the top half of a text page; dense text on its own isn't detected. A PDF screenshot is best effort and is not guaranteed.
• Only marked files can be traced. Materials you delivered unmarked in the past can't be matched later. Re-mark and re-deliver what matters.
• It identifies a copy, not a person. Be careful before accusing anyone.

FAQ

Can I stop students from sharing my course files? Not completely. You can make sharing traceable, which for most people is enough to discourage it.

Will the watermark change how my PDF or images look? It is designed to be invisible at normal viewing size. Compare the original and the marked copy on a screen you trust before using it for a launch.

Do I need a different copy for every student? It's the most precise option, since the match points to one order. If that's too much work, one copy per cohort or per sales channel still tells you which group leaked.

Can I mark my course videos? Yes, on the Business and Enterprise plans: videos up to 10 minutes and 100 MB each, downloaded as MP4. A marked copy can still be traced after re-encoding, trimming or downscaling to 720p, even with metadata stripped. On other plans you can mark the PDFs, slides and images that go with the course.

Should I put the student's name on the page as well? It's optional. A visible name deters casual sharing, but it adds personal data to every page. The invisible label works without it.

What if a file already leaked and wasn't marked? You can't trace that copy. Mark the files from now on and re-deliver the important ones.

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