About BigWatermark

Why we built BigWatermark

Watermarking a single file is easy. Watermarking a folder of 200 photos, a month of invoices or a data-room export is not. Most tools make you open files one at a time, cap the number of files you can process, or require you to upload confidential documents to a remote server you know nothing about.

We wanted something simpler: drop in a whole batch — even a ZIP archive — design the watermark once with a live preview, apply it to everything, and download the results as one ZIP. And we wanted it to be private by default, so you can safely use it for contracts, HR files and unpublished photography.

What we believe

• Your files are yours. PDFs and images are processed entirely in your browser and never uploaded. Word documents, which need a conversion engine, are converted on our server and deleted immediately. We claim no rights to anything you watermark.
• Free means free. No sign-up, no trial, no paywalled batch limit, and we never stamp our own logo on your output. The site is supported by advertising on its content pages.
• Honesty about limits. A watermark is a deterrent and a label, not unbreakable protection. Our guides explain what watermarks can and cannot do, so you can choose the right level of protection.
• Built for batches. Every feature — ZIP in and out, folder upload, page targeting, consistent sizing across mixed images — exists to make large jobs fast and predictable.

How BigWatermark works

BigWatermark is a web application. When you add PDFs or images, your browser reads them from your device and modifies them in memory using JavaScript. PDF watermarks are written directly into each page with the open-source pdf-lib library, previews are rendered with Mozilla’s PDF.js, images are watermarked with the browser’s built-in canvas at full resolution, and ZIP archives are read and written with JSZip.

Word documents are the one exception: browsers cannot lay out .docx files accurately, so they are sent over an encrypted connection to our server, converted to PDF by LibreOffice in an isolated temporary folder with macros disabled, and deleted as soon as the PDF is returned to you. Read the full details in our Privacy Policy.

Who uses BigWatermark

Photographers sending client previews, businesses marking reports as confidential, teachers branding worksheets, real-estate agents stamping listing photos, online sellers protecting product shots, and legal and finance teams labelling copies — anyone who needs the same watermark on many files.

Our editorial standards

The guides on this site are written by the BigWatermark Editorial Team. We only recommend workflows we have tested in the tool, we avoid unsupported statistics, and we update articles when the tool or best practices change. If you spot an error, please let us know.

Get in touch

Questions, bug reports, feature ideas or partnership inquiries are welcome. Email us at support@bigwatermark.com or visit the contact page.