Add your files
Drop one PNG or two hundred. Batch conversion is not a paid feature here.
Some piece of software will only read an uncompressed Windows bitmap, typically an embedded display, a label printer, a game modding tool or an old Visual Basic application.
The compressed PNG is expanded back into raw pixel rows with a BMP header. Nothing is lost visually and the file gets much larger, because that is the entire point of the format.
Transparency does not survive in practice. Our encoder writes a standard 24-bit BMP, so alpha is composited away rather than stored, because the 32-bit alpha variants of BMP are read inconsistently by exactly the old software that needs BMP in the first place.
Because decoding costs nothing. A microcontroller driving a small display can read a BMP row by row with no decompressor at all.
Roughly width times height times three bytes, plus a small header. A 1920 by 1080 image is about 6 MB regardless of content.
Drop one PNG or two hundred. Batch conversion is not a paid feature here.
Windows Bitmap is lossless, so nothing is thrown away in the conversion.
Instant, because the file never went anywhere. Nothing expires, since nothing was stored.