Your files never leave your device

Every other online DPI converter asks you to upload your image to their server. This one does not, and that is the entire point.

The usual way

  • You upload your file to a stranger's server
  • It is processed there and stored, briefly or otherwise
  • You wait for the upload, then the download
  • You trust a retention promise you cannot verify

How this site works

  • The file is read by your own browser
  • The bytes are edited on your machine
  • No upload, so no waiting and no queue
  • You can verify it yourself — see below

What the Tool Actually Does

An image file is not just pixels. Alongside them sits a small block of metadata, and part of that block records the intended print density — the DPI figure. Changing it does not touch a single pixel; it changes the instruction the file carries about how large it should be printed.

That sounds trivial, and technically it is. But a photo tagged 72 DPI drops into Word or InDesign around four times larger than intended, and that oversized placement is what turns a perfectly good image into a blurry print or a rejected upload. Fixing the tag makes the image land at its true size.

How It Works Without a Server

Modern browsers can read a file you select straight into memory, as raw bytes, without sending it anywhere. From there it is a matter of knowing where the number lives in each format:

  • JPEG keeps density in a JFIF APP0 segment near the start of the file, and often also in the Exif block. We update both, so whichever one your print software reads first, it sees the same value.
  • PNG keeps it in a chunk called pHYs, measured in pixels per metre. We rewrite that chunk and recalculate its CRC checksum, or insert one if the file has none.

In both cases the compressed image data is left completely untouched. There is no decode and re-encode step, which is why a JPEG comes out of this tool without the generation loss you get from opening and re-saving it in an editor.

Verify it yourself: open your browser's developer tools, switch to the Network tab, and convert a file. You will see no upload request — because there is nowhere for your image to go. You can also disconnect from the internet entirely after the page loads and the converter still works.

What This Means in Practice

  • No file size limit. There is no upload to time out, so a 200 MB TIFF-sized JPEG is no harder than a small one.
  • No queue, no rate limit, no account. Nothing to sign up for and nothing to pay.
  • Confidential work stays confidential. Unpublished book covers, client photography, medical or legal scans — none of it is transmitted anywhere.
  • Batch processing is free. Multiple files are converted locally and bundled into a ZIP in your browser.

Who Is Behind It

ConvertImageDPI is built and maintained by [[RELLENAR: nombre o razón social]], based in Spain. It started as a personal fix for a recurring annoyance — print services rejecting files over a metadata field that takes seconds to correct — and turned into a public tool once it became clear how many people hit the same wall.

It is a small, independent project, not a company with a support department. Questions go to a real inbox: see the Contact page.

How It Stays Free

Running costs are close to nothing, because there is no server doing image processing — just static files. The site carries analytics to see which guides are useful, and those only run if you accept cookies. There is no paywall and no plan to put the core converter behind one.

Where We Might Be Wrong

The guidance here about print services and Amazon KDP is checked against official documentation, but requirements change. If something on this site contradicts what your printer or platform currently tells you, they are right and we are out of date — please let us know so we can fix it.

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