TIFF is the format of scanners, fax software, print workflows and archives. It is large, often holds several pages in one file, and browsers, phones and most websites can't show it. JPG opens everywhere and is a fraction of the size.
This converter reads TIFFs in your browser, including LZW, Deflate, PackBits, JPEG-compressed and black-and-white CCITT fax files, and greyscale, palette, RGB and CMYK colour. By default every page of a multi-page TIFF becomes its own JPG (name-page-1.jpg, name-page-2.jpg…); choose "First page only" if you just need the cover. Thumbnail copies stored inside the TIFF are skipped, and the TIFF's rotation setting is applied.
Limits: 16-bit images are reduced to 8 bits per channel, which is what JPG stores. TIFFs compressed with JPEG 2000 or Zstandard can't be read. On iPhone and iPad, pages over about 16 megapixels are scaled down to fit Safari's limit; on a computer they keep their full size.