Set 72, 96, 150, 300, 600 or your own DPI in a JPEG or PNG. Pixels untouched, on your device.
To change an image's DPI, this tool writes a new density number into the header of the JPEG or PNG file and leaves every pixel as it is, so the picture and its quality are exactly the same. A JPEG stores density in its JFIF header: a unit set to dots per inch and an X and a Y value. If the file has no JFIF header, one is inserted at the start, which adds 18 bytes. If the file also has Exif fields for XResolution, YResolution and ResolutionUnit, those are set to the same number and the unit to inches, and the result tells you whether that happened. A PNG stores density in a pHYs chunk in pixels per metre, with its own CRC-32 check. The tool converts for you: 72 DPI is 2835 pixels per metre, 96 DPI is 3780 and 300 DPI is 11811. A new chunk is placed before the image data and adds 21 bytes.
DPI says how many pixels are laid across one inch when the picture is printed. It does not add or remove pixels. Print size is the pixel count divided by the DPI: a 4000 by 3000 pixel photo at 300 DPI prints 13.33 by 10 inches, which is 33.87 by 25.40 centimetres, and the same file at 72 DPI prints 55.56 by 41.67 inches. Nothing about the picture became sharper or softer; it only has a different default size on paper. Raising the DPI of a small picture does not add detail either. A 1200 by 900 pixel image at 300 DPI prints 4 by 3 inches, and asking for 12 inches would need a bigger picture, which is a job for Resize image. Many programs ignore the number when a picture is shown on a screen.
JPEG and PNG are supported. WebP has no standard density field, so this tool does not accept it, and neither does it handle GIF, AVIF or HEIC. XMP metadata inside a JPEG, which can hold its own resolution entry, is not edited, and neither is the Exif thumbnail. A JPEG with Exif but no resolution fields gets only the JFIF density. Some editors read one field and some another, so if a program still shows the old number, open the file in a program that reads JFIF or the PNG pHYs chunk. The page reads the start of each file to show the DPI it has now before you change it.
Up to 50 files can be done in one go, all at the same DPI, from 1 to 10,000. The files are not decoded or drawn, so there is no size limit from your device's canvas and no loss of quality, and a photo's location and camera details stay in the file as they were, because only the density fields are rewritten. File names get the DPI added, such as photo-300dpi.jpg. The work is a few bytes of editing in this tab, and no file is sent anywhere.
Add the JPEG or PNG, keep 300 selected, press Set the DPI of 1 image and download the file. A JPEG gets 300 in its JFIF density and a PNG gets a pHYs chunk of 11811 pixels per metre. The pixel size does not change: a 3000 by 2000 photo then prints 10 by 6.67 inches.
No change in quality: the pixels are not decoded or saved again. The file grows by a few bytes only when a header had to be added, 18 bytes for a JPEG without a JFIF header and 21 bytes for a PNG without a pHYs chunk. Otherwise the size stays the same.
No. Sharpness depends on the pixels. A 1200 by 900 pixel picture at 300 DPI prints 4 by 3 inches and at 150 DPI prints 8 by 6 inches, with the same pixels each time. To print larger without a coarse look you need a picture with more pixels, which Resize image can set to an exact size.
Some programs read the Exif resolution or XMP instead of the JFIF density. This tool updates JFIF and, when present, the Exif resolution fields of a JPEG, and the result says if Exif was changed. It does not edit XMP. A program that reads only XMP can still show the old number.
No. WebP has no standard field for density, so this tool accepts JPEG and PNG only. To get a file that can carry a DPI value, convert the WebP to PNG or JPEG with Image Converter, then set the DPI here.
No. Each file is read in this tab, a few header bytes are rewritten, and the result is offered for download, so no server receives your picture. The page counts visits with Google Analytics using rough groups such as 1 to 10 MB, never a file name or an image. Your chosen DPI is remembered on this device.