DPI Changer

Set the DPI saved inside a JPG or PNG to 300, 72, 600 or any value, for the upload form, printer or layout program that insists on it. Only the label is rewritten: the picture is not decoded or saved again, so there is no recompression, no loss of quality, and the file stays the same size to within a few bytes. A JPG can hold the label in three different places that different programs read, and the tool sets all of them so they agree. Do several files at once and download them together. Each file shows the size it will print at the DPI you chose, because a new label does not add pixels, and the DPI Checker tells you whether there are enough. Everything happens on your device, so the images are never uploaded.

How it works

DPI Changer is a web page that does its work on your own device. The file you choose is opened by your browser, changed there and saved from there; it is never sent to a server, so there is no copy of it anywhere to delete, no queue and no waiting for an upload. Most online tools of this kind send your file to their servers and work on it there, and many keep it for a while. This one does not. There is no account, no watermark and no limit on how often you use it, and the result downloads the moment it is ready.

What changing the DPI actually does

An image file is a grid of pixels plus a few notes about it. One of those notes is the DPI: a number that tells software how large the picture is meant to be on paper. A 3,000 pixel wide image labelled 300 DPI says "print me 10 inches wide"; the same image labelled 72 DPI says "print me 41 inches wide". The pixels are identical. Only the note differs.

This tool rewrites that note and nothing else. It does not open the picture, decode it or save it again, so there is no recompression and no loss of quality, and the file stays the same size to within a few bytes. That matters for JPG in particular: an image editor that "changes the DPI" usually re-saves the whole picture, which throws away a little detail every time.

When you need it

• An upload form, a journal, a print-on-demand site or a printer's checker rejects a file because it "is 72 DPI", although it has plenty of pixels.
• A layout program places the picture at an enormous size, because it trusts the label. Set the label and it arrives at the size you expect.
• A client or a brief asks for "300 DPI files" and the pixels are already enough.
• A batch of scans or exports came out with no label, or the wrong one.

What it will not do

It will not make a print sharper. Sharpness comes from how many pixels there are for each printed inch, and a label cannot add pixels. A 600 pixel wide image labelled 300 DPI is still only good for a 2 inch print. To find out whether an image really has enough pixels for the size you want, use the DPI Checker first. Each file in the list shows the size it will print at the DPI you set, which is a quick check in itself.

Where the label lives

A PNG keeps it in one place. A JPG can keep it in up to three, and different programs read different ones: the file's basic header, the camera information block, and a block that Photoshop adds. If they disagree, one program reports 72 and another 300 for the same file. The tool sets every one that is present, so they all agree, and adds the basic header when a JPG has nowhere to hold the label at all.

• It works on JPG and PNG. WebP, GIF and BMP either have no such label or few programs read it; convert those to JPG or PNG first.
• PNG stores the value in pixels per metre, so 300 DPI is saved as 11,811 pixels per metre, which some programs show as 299.999. That is the closest a PNG can hold, and everything treats it as 300.

What it does

• Set 72, 96, 150, 200, 300 or 600 DPI in one click, or type any value
• Only the label changes: no recompression, no quality loss, same pixels
• Sets every place a JPG keeps the label, so all programs report the same number
• Adds a label to files that have none
• Several files at once, downloaded together as a ZIP
• Shows the label each file had, and the print size at the new DPI
• JPG and PNG, with the rest of the file left exactly as it was

Questions

How do I change an image to 300 DPI?

Open the JPG or PNG here, leave the DPI at 300, and download it. The file now carries a 300 DPI label, with its pixels and quality exactly as before. If a form or a printer was rejecting it for being 72 DPI, that is all it needed.

Does changing the DPI reduce the quality?

Not with this tool. It rewrites only the few bytes that hold the label and copies everything else across untouched, so the picture is never decoded or compressed again. Changing the DPI in an image editor usually re-saves the whole file, which for a JPG loses a little detail each time.

Will 300 DPI make my image print sharper?

No. Sharpness depends on how many pixels there are for each printed inch, and a label cannot add pixels. An image 600 pixels wide is good for a 2 inch print at 300 DPI whatever its label says. Use the [DPI Checker](/tools/dpi-checker/) to see whether an image has enough pixels for the size you want.

Why does my image say 72 DPI or 96 DPI?

Because the camera, phone, screenshot tool or website that made it wrote that default into the file, or wrote nothing and your software assumed it. It says nothing about the quality of the image. A 24 megapixel photo labelled 72 DPI has exactly the same detail as one labelled 300.

Why do different programs show different DPI for the same file?

A JPG can keep the resolution in up to three places: its basic header, the camera information block, and a block added by Photoshop. Programs do not all read the same one, so when they disagree you see two numbers for one file. This tool sets every one that is present, so they all match.

Does the file size change?

Hardly at all. If the file already had a label, the new one takes the same space and the size is identical to the byte. If it had none, the file grows by about 20 bytes to hold it.

Why does my PNG show 299.999 DPI instead of 300?

PNG stores resolution in whole pixels per metre, and 300 per inch is 11,811.02 per metre, so the nearest value a PNG can hold works out to 299.9994. Every program rounds it to 300. It is a limit of the PNG format, not of this tool.

Can I change the DPI of WebP, GIF or HEIC images?

Not here. Those formats either have no resolution label or almost no software reads it. Convert the image to JPG or PNG first, then set the DPI.

Are my images uploaded?

No. The images are read and relabelled by your browser on your own device. They are never sent to us or to anyone else, and closing the tab clears them.

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