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Change Image DPI

Set the print density of a JPG or PNG to 72, 150, 300 or 600 DPI by rewriting the metadata field, without resampling a single pixel.

Choose a JPG or PNG

The density field is rewritten in this tab. Nothing is uploaded.

Result

Choose a JPG or PNG to see its current density.

The current DPI, the print size at the new value, and a download appear here.

Your file is never sent to a server. It is read and processed by your own browser, and the results are not stored.

How to use it

  1. Choose a JPG or PNG. Its current density and pixel dimensions are read from the header.
  2. Pick a preset or type a value from 1 to 1200 DPI.
  3. Set the DPI, check the reported field, and download the rewritten file.

Limits worth knowing

  • JPEG and PNG only. WebP has no density field, and HEIC, TIFF and RAW are not decoded here.
  • Values from 1 to 1200 DPI are accepted. The tool does not resample pixels, so a high DPI value does not add detail.
  • In JPEG, an existing JFIF field is replaced. If there is no JFIF field, one is inserted; EXIF resolution tags are patched only when they already exist, because adding tags would require rebuilding the whole EXIF offset table.
  • The rewrite is lossless and copies every non-density byte, including the compressed image data.

DPI is metadata, not resolution

A digital image has pixels. DPI is a hint for a printer or layout program: how many of those pixels should occupy one inch of paper. Changing the hint changes the physical size, not the amount of detail. A 3000-pixel-wide photo at 300 DPI prints 10 inches wide; at 72 DPI it prints about 41 inches wide.

That is why “increase DPI to 300” cannot make a small image print sharply at a large size. The pixels are the limit. A print shop asking for 300 DPI is asking for enough pixels at the intended dimensions, not for a tag alone.

What the file rewrite does

For JPEG the tool walks the marker segments, finds the JFIF APP0 segment and writes the new density and units. If no JFIF segment exists, it inserts one directly after the start-of-image marker; nothing after it needs its offsets changed. Existing EXIF resolution tags are patched in place when present.

For PNG it writes or replaces the pHYs chunk immediately after IHDR, converting DPI to pixels per metre. The encoded image data is never decoded or re-encoded, so the picture is byte-for-byte the same.

Frequently asked questions

Does Change Image DPI upload my files to any server?

No. Change Image DPI runs in your browser, and the file is read there rather than sent to a server for processing. Our host still sees ordinary page-request metadata, which is described on the privacy page.

Is Change Image DPI free to use?

Yes, Change Image DPI is free, with no paid tier, no account, and no watermark added to your output. The limits are technical rather than commercial: file size, page count and supported formats are listed on this page.

What file formats and sizes are supported?

Change Image DPI supports .jpg, .jpeg, .png files up to 25MB directly in your browser.

Does changing DPI increase image quality?

No. DPI is a print-density tag; the pixel dimensions do not change. A 1200×800 photo is still 1200×800 at 72 or 300 DPI. What changes is the physical size a print pipeline derives: the same pixels are printed smaller at a higher DPI.

Which field is rewritten?

For JPEG, the tool updates the JFIF density field and, where present, the EXIF resolution tags. For PNG it writes the pHYs chunk in dots per metre, which is how PNG stores the same idea. Every other byte, including the compressed image data, is copied through unchanged.

Why is WebP not supported?

The WebP container has no density field. Writing one would mean inventing a place for it that readers do not agree on, so the tool refuses WebP rather than claiming a value the format cannot store.