Convert TIFF to PNG

PNG is the right target when the TIFF is a graphic rather than a photograph: a logo from a print designer, a technical drawing, a map, a chart from a lab instrument, a screenshot saved by macOS in an older setting, or a black-and-white document scan. Like TIFF, PNG is lossless, so every pixel comes through unchanged, but unlike TIFF it displays in every browser and in almost every app and website.

Transparency survives the trip. TIFFs saved from Photoshop, Illustrator or GIMP with an alpha channel become PNGs with the same see-through areas, so a logo still sits cleanly on a coloured page. Files with 16 bits per channel are brought down to 8, which is all a screen shows.

Chrome, Edge and Firefox cannot decode TIFF, so the page includes UTIF.js, an open-source TIFF reader bundled with the site. It reads uncompressed, LZW, Deflate, PackBits and JPEG-compressed TIFFs, plus CCITT fax encoding. A bilevel fax page often comes out as a PNG of a few dozen kilobytes, much smaller than the same page as a JPG.

For photographs, PNG files get big: a 24-megapixel camera TIFF becomes a PNG of 40 MB or more. If the picture is a photo that is going to be shared rather than edited, TIFF to JPG is the better choice. Multi-page TIFFs give a PNG of the first page here.

Some everyday places TIFFs turn up: macOS used to save screenshots as TIFF and still does when the default was changed; Windows Snipping Tool and many scanner utilities offer it as an option; GIS software exports map tiles and elevation images as GeoTIFF; microscopes, gel imagers and astronomy cameras write it because it stores raw sensor values. The geographic and scientific tags in those files are not carried into the PNG, only the picture itself.

If a TIFF fails to convert, it is usually one of a small set of rare variants: floating-point pixel data from scientific instruments, tiled files larger than your device can hold in memory, or a proprietary compression from old imaging software. The error message says so, and nothing about the file has been sent anywhere in the attempt.

Black-and-white documents deserve a special mention. A one-bit TIFF of a typed page stores only black and white pixels. The PNG keeps every one of them pure black or pure white, and because two colours compress very well it stays small, where JPG would add grey smudges around every letter. That makes PNG the better target for contracts, forms and letters scanned in monochrome mode.