Calling something "a TIFF file" is a bit like calling something "a ZIP file" without saying what's inside it. TIFF, short for Tagged Image File Format, doesn't mandate a single way of storing pixel data. It defines a tagged container structure that can hold pixel data compressed in several different ways, including completely uncompressed, LZW lossless compression, ZIP compression, or even JPEG compression embedded inside the TIFF wrapper. This is why two TIFF files of the same photo can be wildly different sizes. An uncompressed TIFF stores every pixel exactly as captured with no reduction at all, which is why scanner and professional camera software favors it for archival purposes. A 600 DPI scan of a single page document can easily be 30 to 50MB as an uncompressed TIFF, compared to a few hundred kilobytes as a JPEG.
Scanner manufacturers default to TIFF for a straightforward reason: it guarantees no generation loss. A document scanned once and saved as TIFF can be reopened, re-saved, and processed through OCR software repeatedly without any compression artifacts accumulating, which matters for archival and legal document workflows where fidelity to the original scan is important. The tradeoff is that nobody wants to email a 40MB file or upload it to a web form, which is the gap this conversion fills. The scan stays archived as the original TIFF if needed, while the JPEG version becomes the practical copy that actually gets shared.
Why multi-page TIFFs exist and what happens to the other pages
Multi-page TIFF is a real and still-used capability of the format, where a single TIFF file contains several complete images stored as separate frames within one file, similar in concept to how a PDF holds multiple pages. This traces back to fax machine standards, where incoming faxes were commonly saved as multi-page TIFF files with each fax page becoming one frame in the file. Many office scanners inherited this behavior and still default to producing a multi-page TIFF when you scan a multi-sheet document through the automatic document feeder, bundling every scanned page into one file rather than producing separate files per page.
When you convert a multi-page TIFF here, only the first page comes through as the output JPEG. The remaining pages aren't damaged or lost from your original file, they simply aren't part of this particular conversion, since JPEG has no concept of multiple pages within one file the way TIFF or PDF do. If you need every page extracted individually, or you need the whole multi-page document combined into a more shareable format, converting the full set of pages and assembling them with the JPG to PDF tool produces a single shareable document that, unlike JPEG, does support multiple pages natively.