When the TIFF is a scanned document, a diagram, or anything where the exact pixel values matter, PNG is the right target and JPEG is the wrong one. Both TIFF and PNG are lossless, so this conversion changes how the image is stored without changing what it contains — every value survives intact, and the file usually gets a lot smaller at the same time.
Why lossless matters for scans specifically
Scanned text is the clearest case. JPEG compression works by discarding fine high-contrast detail, which is precisely what letterforms are made of, so small print picks up a soft haze and thin strokes start to break up. PNG leaves the characters exactly as the scanner captured them. The same argument applies to line drawings, engineering diagrams, sheet music, maps and anything that will be read rather than admired.
It applies with more force to scientific and medical imaging, where pixel values are measurements. A JPEG changes those values by design. If anyone is going to analyse the image rather than look at it, lossy compression is not an option.
The size usually drops sharply anyway
- Uncompressed TIFF scans of text often shrink by 90% or more as PNG, because large white areas compress extremely well.
- Line art, diagrams and bilevel scans see similar reductions.
- Photographic scans benefit least — PNG is not efficient on photographs — and are the one case where JPEG is worth considering.
- TIFFs that were already LZW-compressed shrink less, since some of the work was done.
Things TIFF can do that PNG cannot
Multi-page files give you the first page only. TIFF was built to hold whole documents in one file and PNG holds a single image, so a twenty-page fax becomes one page. Convert to PDF instead if you need to keep them together.
CMYK is converted to RGB, since PNG has no CMYK mode. For screen use that is correct and expected, but if the file is a print master destined for a press, converting it will change how the colours separate — keep the TIFF for that. Embedded colour profiles, layers, alpha masks and the extensive metadata TIFF supports are also not carried across.
Why the TIFF would not open in the first place
No browser displays TIFF, and on most computers the extension belongs to whichever imaging application was installed last. That is not an accident: TIFF permits so many internal variations that implementing it fully is a significant undertaking, and browser vendors never judged it worth doing. Converting to PNG turns the file into something every piece of software on your machine already understands, without giving up the exactness that made TIFF the right choice for the scan originally.
Everything runs inside this tab. Scanned contracts, records and identity documents never leave your device, which is the whole reason to convert them here rather than on someone else’s server.