How images become a PDF — entirely inside your browser

Scans, receipts and ID photos are exactly the kind of files you should not be uploading to an anonymous converter. The good news is that building a PDF is far simpler than it looks, and a browser has everything required.

A PDF is a list of objects

At its core, a PDF file is a header, a set of numbered objects, a cross-reference table of byte offsets, and a trailer. For an image-only document you need four kinds of object: a catalog, a page tree, one page per image, and an image XObject holding the pixels.

JPEG goes in untouched

PDF supports a `DCTDecode` filter, which is JPEG. That means a JPEG's compressed bytes can be written straight into the file with no re-compression step and no decoding library. The Images to PDF tool draws your image on a canvas, exports it as JPEG at high quality, and embeds those bytes as the page's only content — which is why the conversion is instant even for large batches.

The trade-off: JPEG has no alpha channel, so transparent PNG areas are flattened onto white.

Fit-to-image versus A4

**Fit to image** gives each page the exact aspect ratio of its source, plus your margin. Nothing is cropped, nothing is letterboxed — ideal for screenshots and mixed-orientation photos.

**A4 or US Letter** produces a uniform document where every image is scaled to fit inside a fixed page. Choose this when the PDF will be printed or submitted to a form that expects a standard size.

Getting a smaller file

PDF size is dominated by the images. Resize a 4000px phone photo down to around 1600px before converting and the result is typically a fraction of the size with no visible difference on screen. Compress first, convert second.

Nothing leaves your device

Canvas decoding, JPEG encoding and byte assembly all happen in the tab. There is no upload, no queue and no temporary file on a server to expire — the PDF simply appears in your downloads folder.