Set 300 DPI without re-encoding the pixels — JPEG and PNG, whole batches at once, with no upload.
Only the density tag changes. Pixels are copied through untouched, so the picture looks identical and the file size barely moves — a bigger DPI number cannot add detail that was never there.
Everything runs locally in your browser. Nothing is uploaded to any server — close the tab and your files are gone.
Drag in as many as you like, or click to browse. Each file is identified by its actual header bytes, so a mislabelled extension won’t slip through. Nothing is uploaded — your browser reads the files directly.
Tap 300 for most print work, or type any value from 1 to 2400. One setting applies to the whole list, and changing it re-runs every file instantly.
Each row shows the pixel size and what it comes to on paper at the new DPI, in millimetres and inches. If that’s smaller than you need, the image needs more pixels — no DPI value can conjure them.
Take files one at a time, or the whole batch as a ZIP. Each is saved as name-300dpi.jpg, so your originals stay exactly where they are.
Two very different operations both get called “changing the DPI”, and mixing them up is what turns a five-second fix into a ruined image. Photoshop’s Image Size dialog does the first when Resample is off and the second when it is on. This tool only ever does the first — it has no resampling mode at all.
| What happens to… | Rewriting the density tag (this tool) | Resampling the pixels |
|---|---|---|
| Pixel dimensions | Unchanged. A 2400 × 3000 px file stays 2400 × 3000 px. | Changed. Pixels are interpolated into existence or discarded. |
| Image data | Copied through byte for byte — a JPEG’s scan data and a PNG’s IDAT chunks are never decoded. | Decoded, interpolated and re-encoded in full. |
| File size | JPEG: identical when the file already has a JFIF header, since five bytes are overwritten in place; 18 bytes larger when one has to be added. PNG: 21 bytes larger when a pHYs chunk is new. | Rises or falls roughly in step with the pixel count. |
| Visible quality | Identical. Nothing is re-compressed, so repeating the operation costs nothing. | Softening on the way up, lost detail on the way down, and generation loss with every JPEG re-save. |
| Printed size | Changes — that is the entire point of the operation. | Can stay exactly the same while the pixel count moves underneath it. |
| Other metadata | Left alone. EXIF resolution fields are corrected in place when they already exist, and never inserted where they don’t — growing an EXIF directory would shift every offset behind it. | Depends entirely on the editor; many strip or rewrite the block. |
If the print size you need is larger than the pixels can carry, no tag will fix it — that job needs a re-export from the original artwork at a bigger pixel size.
Most DPI requests arrive with no explanation attached. These four cases cover almost all of them.
Nine times out of ten they are reading the density tag, seeing 72, and stopping there. Check the pixels before you panic: pixels ÷ 300 × 25.4 gives the printed size in millimetres. If that already covers the piece you are printing, the artwork was print-ready all along and only the label was wrong. Our A4 pixel reference shows the target pixel counts for a standard sheet.
Plenty of cameras and export dialogues hardcode 72, or write no density field at all, and it says nothing about image quality. A 6000 × 4000 file tagged 72 DPI prints 508 × 339 mm at 300 DPI — larger than an A3 sheet. Retagging it is a labelling correction, not an upgrade. To sanity-check any other file, the px to mm converter takes you from pixels to paper.
It doesn’t. Browsers size an image from its pixel dimensions and your CSS; the density tag is ignored on the way to the screen. Setting a web image to 72 DPI makes it neither smaller nor faster — the file is byte-for-byte what it was. If the goal is a lighter page, you need fewer pixels or stronger compression, which is what the image compressor is for.
Drop the batch in, pick one target, and every JPEG and PNG in the list is retagged at once — each saved as name-300dpi.jpg so the originals stay untouched, individually or as a single ZIP. Files in other formats are skipped rather than silently mangled, because only JPEG and PNG have a standard place to record density. The 300 DPI guide walks through the whole handoff.
No. DPI is a note attached to the file saying how large one pixel should be printed — it never creates pixels. A 600 × 600 photo holds exactly 600 × 600 pixels of detail at 72 DPI and at 300 DPI alike; only the printed size changes, from about 212 mm across down to about 51 mm. Sharpness comes from having enough pixels in the first place.
It is, as long as the image already has the pixels, and that is what the request usually comes down to. Do the arithmetic: pixels ÷ 300 × 25.4 gives millimetres. If a 3543 × 2362 image lands on the 300 × 200 mm you need, the file was print-ready all along and only the tag was wrong — which is exactly what this tool fixes. If the result comes out far too small, re-export the artwork at a larger pixel size instead.
Because the image data is copied through byte for byte. A JPEG usually changes by five bytes — the density unit and the two density values in its JFIF header — and a PNG grows by 21 bytes when it needs a new pHYs chunk. Nothing is decoded or re-compressed, so there is no generation loss even if you run the same file through repeatedly.
They are the two common formats with a standard place to record density: the JFIF and EXIF fields in JPEG, the pHYs chunk in PNG. WebP has no standard density field at all, so a print shop would have nothing to read, and inventing one would mean rebuilding the container. GIF has none either. On the vector side, PDF and SVG state physical size directly and don’t use DPI.
The EXIF block is left byte for byte as it was, and the DPI goes into the JFIF header, which print workflows read. Inserting a tag into an EXIF directory would shift every value offset stored behind it and quietly break the rest of the metadata, so this tool never does that. When EXIF already carries XResolution and YResolution, those are rewritten in place so the two headers never disagree.
In your browser, on your own machine. The file is read into memory, a handful of header bytes are rewritten, and the result is handed straight back to you as a download. There is no upload and no server copy — once the page has loaded, the conversion needs no network at all.
No. A 2400 × 3000 px image stays 2400 × 3000 px. The tool copies the compressed image data unchanged and rewrites only the JPEG or PNG density metadata, so the new DPI affects the calculated print size rather than the number of pixels.
Usually not. Browsers and most screen-based apps size an image from its pixel dimensions or layout settings, not its print-density tag. DPI matters when printing or when an application uses the tag to calculate a physical size in inches or millimetres.
Yes. Add multiple JPEG or PNG files, choose one target from the 72, 150, 300 or 600 DPI presets, or enter any whole number from 1 to 2400. The setting is applied to every file in the list, and the results can be downloaded separately or together as a ZIP.
Resample off. With it unticked, Photoshop keeps the pixel grid exactly as it is and only changes the resolution figure, which is the same operation performed here. Tick Resample and Photoshop rebuilds the pixels to match the new numbers — that is a different job, and one this tool deliberately does not do.
It reads the density fields directly. In a JPEG that means the JFIF header, including its unit byte, so a file that stored dots per centimetre is converted rather than misread; if there is no usable JFIF value it falls back to the EXIF resolution tags. In a PNG it reads the pHYs chunk, which counts pixels per metre, and converts back to inches. A file carrying none of these shows as having no DPI set, which is normal and not a fault.
Not necessarily. The tag lives in the file header, so any application that re-encodes the image writes whatever density its own export settings specify — which is exactly how a 72 DPI file appears in the first place. Retag at the end of your workflow, right before handing the files over, rather than in the middle of it.
300 is the safe answer for anything printed on a press or a photo printer, and it is what most print shops mean by “high resolution”. 600 suits line art, small type and scans. For screen-only work the tag rarely matters at all. Whichever you pick, read the print size the tool shows for each file — that number tells you far more than the DPI figure on its own.