Does changing DPI make the image sharper?

No. With resampling off, not a single pixel changes — DPI is just a number written into the file. Sharpness comes from the pixel count, not from that number; changing it cannot conjure detail that was never captured.

The print shop wants 300dpi — what do I do?

First check whether you have the pixels: pixels needed = physical size in inches × 300. Printing 10×15 cm (about 3.94×5.91 in) needs roughly 1181×1772 pixels. If you have them, set DPI to 300 and you are done. If you do not, changing the number achieves nothing — you need a larger original.

Why does my exported WebP have no DPI?

WebP has no general resolution field. PNG has the pHYs chunk and JPG has the JFIF density field; WebP has no equivalent, so there is nowhere to write it. Export PNG or JPG when the file needs to carry a DPI.

Is it free? Is my image uploaded?

Free, no sign-up, no usage limit. Nothing is uploaded either — it all runs in your own browser.

Change image DPI · set it to 300

DPI 1–2400, pixels untouched. Local processing, nothing uploaded.

Use it online now

Open Image Size and set the resolution to 300 — not a pixel changes.

First, what DPI actually is: it does not affect sharpness. It is a number written into the file that tells the printer "put this many pixels into an inch", which determines how large the print comes out. Physical size = pixel count ÷ DPI — a 3000-pixel-wide image prints 10 inches wide at 300dpi and 41.7 inches wide at 72dpi, with exactly the same pixels. So with resampling off, changing DPI leaves every pixel alone. The range is 1 to 2400. On export the number really goes into the file: PNG carries it in the pHYs chunk, JPG in the JFIF density field; WebP has no resolution field, so it carries no DPI — export PNG or JPG if you need one. One more thing that is not obvious: exporting at N× also multiplies the effective DPI by N, so the physical size stays the same after scaling up. It all runs in your own browser; the image is never uploaded.

Key features

DPI 1–2400

72 for the web, 150 for everyday printing, 300 for press, 600 for fine work.

Pixels untouched

With resampling off, not a single pixel changes — only the number written into the file.

Really written into the file

PNG in the pHYs chunk, JPG in the JFIF density field — print software reads it.

Runs locally

The image is never uploaded. Close the tab and nothing is left.

How to use

1
Add an image

Drag it into the box, or press Ctrl+V to paste.
2
Open Image Size

Pick Image Size from the Image menu.
3
Set resolution to 300

Range 1 to 2400. Leave resampling off if you do not want the pixels changed.
4
Export PNG or JPG

The DPI goes into the file; WebP has no such field and cannot carry it.

FAQ

Does changing DPI make the image sharper?: No. With resampling off, not a single pixel changes — DPI is just a number written into the file. Sharpness comes from the pixel count, not from that number; changing it cannot conjure detail that was never captured.
The print shop wants 300dpi — what do I do?: First check whether you have the pixels: pixels needed = physical size in inches × 300. Printing 10×15 cm (about 3.94×5.91 in) needs roughly 1181×1772 pixels. If you have them, set DPI to 300 and you are done. If you do not, changing the number achieves nothing — you need a larger original.
Why does my exported WebP have no DPI?: WebP has no general resolution field. PNG has the pHYs chunk and JPG has the JFIF density field; WebP has no equivalent, so there is nowhere to write it. Export PNG or JPG when the file needs to carry a DPI.
Is it free? Is my image uploaded?: Free, no sign-up, no usage limit. Nothing is uploaded either — it all runs in your own browser.

Try Change image DPI · set it to 300 now

Runs fully in your browser · no install · no signup · images never uploaded

Use it online now