Search for a free image compressor and you will get hundreds. They are not the same kind of free, and the differences only show up after you have handed over your files.

Here is what to look for, and why each one matters more than it first appears.

1. Is there a watermark?

The oldest trick. The tool is free, the output has a logo in the corner, and removing it costs money. Sometimes it is disclosed on the pricing page and sometimes you find out after processing two hundred files. Check before the batch, not after.

2. Does it want an account?

An email address is rarely needed to run a compression algorithm. When a tool asks for one anyway, the account is the product being built, not a feature you are being given. Compressing a photo does not require anybody to know who you are.

3. What is the file size cap?

Browser-based tools almost always have one — 5 MB is common, sometimes 10. That is fine until you point it at a RAW export or a 60-megapixel file, at which point the free tier quietly becomes a demo. Look for the limit before you plan a workflow around the tool.

4. How many files at once?

Twenty at a time, then a wait, then twenty more, is not a free tool — it is a paid tool with a friction tax. If you routinely handle folders rather than files, batch capacity is the feature that decides whether you keep using it. Ours is covered in compressing a whole folder.

5. What happens to your files?

This is the one that actually costs you something. An online compressor works by uploading your images to somebody else’s computer. Read the terms and you will usually find a retention window, sometimes a licence to process and store, and occasionally something considerably broader.

For a photo of your lunch, who cares. For client work under an NDA, unreleased product shots, or anything with a face or a document in it, that upload is the whole risk. We went into this properly in why your photos should never leave your computer.

6. Does it work with the network off?

The most honest test there is, and it takes ten seconds. Disconnect and try to compress something. A tool that keeps working was never sending your files anywhere. A tool that stalls was — whatever the marketing said.

Why a desktop app changes the arithmetic

Most of the limits above exist because someone else is paying for the processing. Every image compressed in a browser tab costs the operator bandwidth and CPU, so caps, queues and accounts are how that bill gets managed. It is a reasonable business model; it is just not free in the sense most people mean.

Run the work on your own machine and that bill does not exist. No upload, so no size cap. No shared queue, so no waiting behind other people. A 60-megapixel file is handled at the speed of your own disk. There is more on this in the three things a browser tab cannot do.

Where we stand

Since this is our blog, it is only fair to answer our own checklist.

  • No watermark, ever.
  • No account, and no email address collected to download it.
  • No file size cap and no batch limit — the constraint is your own disk.
  • Nothing is uploaded. The app works with the network cable out.
  • This website carries advertising. That is what pays for it, and we would rather say so than pretend the hosting is magic.

You can read more about who builds it on the about page, or just download it and run the network test yourself.