Check width, height, DPI, color depth, and file size of multiple images at once.
Drop in one image or several at once and the tool reads each file's header to report pixel dimensions, DPI, color depth, and byte size together in one pass, so a mixed batch of PNGs, JPEGs, GIFs, and WebPs comes back comparable. Parsing happens locally in the browser; no file is uploaded. The thing users most often get wrong is DPI: it is a print hint stored in metadata, not a property of the pixels. Two files with identical 1200x800 pixels can read 72 DPI and 300 DPI, and editing the tag never changes the pixel count.
A concrete input and expected output from the current implementation.
Input
A 64x64 PNG saved from a graphics editor with 8-bit RGBA color and a 72 DPI print tag (2835 pixels per meter).
Expected output
Width 64 px, height 64 px, DPI 72, color depth 32-bit (RGBA), plus the file's byte size as read from disk. Content, sharpness, and compression are not reported.
PNG headers store dimensions and a pixels-per-meter tag: 2835 ppm converts to 72 DPI (2835 / 39.37 = 72.0). Four 8-bit channels add up to 32-bit depth. File size is read from the actual file and cannot be derived from the other fields, since it depends on the compressed content.
Every format keeps this information differently. PNG puts width, height, bit depth, and color type in its IHDR chunk and resolution in a pHYs chunk; JPEG records dimensions in frame-header markers and density in a JFIF segment; GIF and WebP carry their own header fields. The tool resolves each format's layout and returns one comparable row per file, which is why a mixed batch works in a single pass.
DPI comes from the file's resolution tag and controls only physical print size. PNG stores pixels per meter: 2835 ppm converts to 72 DPI, 11811 ppm to 300 DPI. Screenshots and web downloads often carry no tag at all, so no DPI is shown for them. A 1200-pixel image tagged 300 DPI prints 4 inches wide; the same pixels tagged 72 DPI print 16.7 inches. On screen both are 1200 pixels wide.
Only roughly. Print size equals pixels divided by DPI: a 3000x2000 image prints 10 x 6.7 inches at 300 DPI and 41.7 x 27.8 inches at 72 DPI. Sharpness also depends on the original capture, compression, and viewing distance, which no header check can see. If the tag is missing, the image can still print fine: the printer rasterizes at its own resolution.
Because size records how well the image compressed, not its dimensions or quality tags. A flat-color PNG of any size can compress to a few hundred bytes, while a grainy photo with the same pixel count runs into megabytes. The checker reports size so you can spot outliers and estimate download or print times, but it cannot tell you which image is better.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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