The PNM file format stores data in the PNM format. Converting to ICO produces a image file that bundles multiple raster images at different resolutions (16x16 through 256x256) into a single file for use as application icons. This renders each page as a raster image, making the content viewable without a document reader. Each page is rendered at the specified DPI and saved as a separate image; text in the output is no longer selectable. This makes ICO the practical choice when the destination system requires it or when the original format is not supported by the target application. 1converter runs this conversion on the server: your file is uploaded encrypted over HTTPS, converted using trusted open-source libraries, and the output is held for 24 hours before automatic deletion.