Patent Marking for Online Products: What the Law Requires and Why It Matters

If you sell a patented product — physical or digital — and you fail to mark it correctly, you may lose the right to collect damages for past infringement. That rule is not intuitive for software founders and e-commerce operators who think of "marking" as something stamped on hardware. But the law applies broadly, and the consequences of ignoring it are real.

What Patent Marking Actually Is

Patent marking is the practice of notifying the public that a product is covered by one or more patents. Historically this meant physically printing "Patent" or "Pat." followed by a patent number on the product itself or its packaging. The legal purpose is notice: if an infringer cannot claim they were unaware a product was patented, they cannot argue innocent infringement to reduce damages.

The relevant U.S. statute is 35 U.S.C. § 287. It does not require marking — but it conditions your damages on it. If you hold a patent, sell a covered product, and never mark it, you can only collect damages from the date you actually notified the infringer (typically when you filed suit or sent a cease-and-desist letter). Everything before that date is off the table.

How Virtual Marking Changed the Game for Digital Products

In 2011, Congress amended § 287 to allow "virtual marking." Instead of printing every patent number on every product, a patent holder can mark products with the word "Patent" or "Pat." followed by a URL that lists the applicable patents. That URL must be freely accessible to the public — no login, no paywall.

For internet and e-commerce companies, this matters a great deal.

Where to Put the Mark on a Digital Product

• Software applications: A footer in the app, an "About" screen, or a dedicated legal/patents page accessible from the app's settings.
• SaaS platforms: A persistent footer link on the web interface, or a standalone patents page linked from your main site's footer.
• E-commerce storefronts: Product listing pages, product detail pages, or packaging inserts for physical goods shipped to customers.
• APIs: If your patented method is embodied in an API, mark your developer documentation and terms-of-service page.

The key is that the mark must be associated with the product itself, not buried in a corporate filing or an investor relations page.

Keeping the Marking Page Current

Virtual marking shifts the maintenance burden to your URL. Every time you receive a new patent that covers a product, add it. Every time a patent expires or is licensed away under terms that shift marking obligations, update accordingly. A stale or inaccurate marking page can create legal problems of its own — false marking (claiming patent protection you do not actually have) carries its own penalties under § 292.

A practical approach: treat your patents page the way you treat your privacy policy. Assign someone ownership of it, tie updates to your patent prosecution calendar, and review it whenever a patent issues or lapses.

Method Patents and the Marking Exemption

There is an important carve-out you should know. Section 287's marking requirement applies to patented articles — products you make, offer for sale, or sell. If your patent covers only a method (a process or way of doing something), and you do not sell a physical or digital article embodying that method, the marking requirement does not apply. You can sue for damages going back to the date of infringement without ever having marked anything.

Many software patents are drafted as method claims precisely because the invention is a process rather than a thing. But if your patent has both product and method claims — which is common — the product claims can still trigger the marking requirement even if the method claims would not on their own. This is worth discussing with your patent counsel when claims are being drafted.

Practical Takeaways

• Patent marking is optional, but skipping it caps your damages at the date you gave actual notice to the infringer — not the date they started infringing.
• Virtual marking (a URL listing your patents) is fully valid and is the right approach for software, SaaS, and e-commerce products.
• Your marking URL must be publicly accessible without any login or barrier.
• Treat your patents page as a living document: update it when patents issue, expire, or when marking obligations shift under a license.
• Pure method patents are exempt from the marking requirement, but mixed patent claims (product and method) can still trigger it.
• Review your marking practices whenever you launch a new product feature that a patent covers — the obligation attaches at the point of sale or public availability, not at filing.

This guide is general education, not legal advice, and does not create an attorney–client relationship. For your specific situation, talk to a registered patent attorney.