No browser can open a TIFF. This page carries a decoder, and handles multi-page files.
TIFF is the one common image format browsers genuinely cannot read, and that is an absence of support rather than a gap in it. This page loads a decoder only when you pick a file, then converts on your device with nothing uploaded.
Drag, drop or paste · TIF or TIFF · multi-page supported
Converts TIFF to JPG, PNG or WebP. Multi-page files get a page selector, so you can convert any page rather than only the first. The decoder is fetched only after you choose a file.
Browsers decode JPG, PNG, WebP, GIF, BMP and AVIF. TIFF is not on that list and never has been. Dropping one into a browser window gives you a download prompt or a broken icon, and most web tools that claim to convert TIFF are uploading it to a server running ImageMagick.
The reason is that TIFF is less a format than a container. It can hold uncompressed data, LZW, PackBits, JPEG or CCITT fax compression, at any bit depth, in several colour models, with pages nested inside. Supporting it properly means supporting a dozen formats at once, so browsers never did.
TIFF is one of the few image formats that holds several pages in a single file, which is why scanners and fax software default to it. A scanned ten-page document is frequently one TIFF.
Most converters silently take page one and discard the rest, which is how people end up thinking nine pages vanished. When this page sees more than one, it shows a selector and converts whichever page you pick.
TIFF is often chosen precisely because it can be lossless and carry 16 bits per channel. Converting to JPG gives up both, since JPG is lossy and 8-bit. For a scanned document that does not matter. For an archival photograph or a print master it does.
If the TIFF is a master you intend to keep, convert a copy and keep the original. If you need a lossless working file, pick PNG rather than JPG, though PNG is still 8 bits per channel.
Keep going without re-uploading — your image carries over to the next tool automatically.