About MergePNG

Why this site exists

MergePNG started with a simple annoyance: merging a few screenshots meant either uploading them to a random website and hoping for the best, or opening a desktop editor for a ten-second job. Screenshot folders often contain things you would rather not hand to a third-party server, receipts, work-in-progress designs, family photos, so the upload-first approach that most free tools take is a poor default.

Every tool on this site therefore runs entirely in your browser. The files you add are read by the page, processed with the Canvas API and WebAssembly, and written back to your downloads folder. No upload happens at any point. You can pull your network cable after the page loads and everything still works.

How we build the tools

The merge engine composites your images on a single canvas and re-encodes once, keeping PNG transparency where the format allows it. PDF output is assembled by pdf-lib in the page. PNG compression uses oxipng compiled to WebAssembly for the lossless path, and compares encodings to pick the smallest honest result when you use Auto mode. Duplicate detection hashes each file with SHA-256, the same construction used in software distribution, to flag exact copies before you merge them.

When a browser has a hard limit, we would rather tell you than hand you a broken file. Mobile Safari, for instance, caps a canvas at roughly 16.7 million pixels, so large merges are scaled down with a visible notice instead of silently failing.

How the site is funded

Ads, and nothing else. There is no pro tier, no account system, and no paid features. Advertising keeps the tools free, and the ads never gate functionality: they sit around the tool, never inside your file flow.

Who is behind it

MergePNG is an independent project by a small team of developers who build browser-based utilities. We can be reached through the Contact page, and we read everything, especially bug reports with a sample file description and your browser version.