When an image works better than a PDF
PDF is the right format for documents, but plenty of places only accept pictures:
- Social networks and messengers, where a PDF shows up as a file icon while an image appears inline.
- Website builders, CMS galleries and marketplaces that take JPG or PNG uploads only.
- Online forms that ask for "a photo of the document" but you have the PDF version.
- Slides you want to post or embed one by one.
- Quick previews or thumbnails of a report cover for a newsletter.
Converting each page to a JPG solves all of these, at the cost of turning live text into pixels.
Resolution, explained with real numbers
PDF pages are measured in points, and one point is 1/72 of an inch. That is why the resolution options are expressed as multiples of 72 dpi:
- 1x (72 dpi): an A4 page becomes 595×842 pixels, a US Letter page 612×792. Readable on a phone for large text, too small for body text when zoomed.
- 2x (144 dpi): A4 becomes 1190×1684 pixels. Sharp on most laptop and phone screens, the default and the right choice for messengers, web pages and on-screen reading.
- 3x (216 dpi): A4 becomes 1786×2526 pixels. Use it when people will zoom into small print, for detailed drawings, or for printing at the original size.
The pixel count grows with the square of the multiplier: a 3x image has about nine times as many pixels as a 1x image, and its file is several times larger. For 30-page documents this adds up fast.
For a slide deck shown in a chat, 2x is plenty. Save 3x for pages with fine print or technical drawings.
For printing, 216 dpi gives good results at the original page size for most documents. Professional printing usually asks for 300 dpi, which is above what this tool produces; for a print shop, send the PDF itself.
Choosing JPEG quality
The quality slider runs from 50 to 100, default 90. JPEG was designed for photographs, and it handles smooth gradients well but struggles with sharp edges, which is exactly what text is. At lower settings you see faint ghosting, called ringing, around letters.
- 90 to 100: text edges stay clean. Good for documents, spreadsheets and anything with small type.
- 75 to 85: much smaller files with barely visible artifacts on photos and illustrations. A good fit for brochures or photo-heavy pages.
- 50 to 70: noticeable blur around text. Only for previews and thumbnails.
Resolution affects quality more than the slider does. A page at 2x with quality 80 usually looks better than the same page at 1x with quality 100.
What the output looks like
Pages are rendered with PDF.js, the PDF engine used in Firefox, so they look the way the document looks in a browser viewer. Fonts embedded in the PDF are used for rendering. A few points to know:
- Each page becomes one image, named after the file with a page suffix, for example
brochure-page-3.jpg. Previews appear in a grid, and a multi-page document downloads as a ZIP. - Transparent areas become white, since JPEG has no transparency.
- Text in the images is no longer text. It cannot be searched or copied. If you need it back, image to text can read it, but extracting directly from the PDF with PDF to text is more accurate when the PDF has a text layer.
- Links and form fields stop being interactive; at most their printed appearance remains.
- All pages are converted. To export only a few, cut them out first with split PDF and convert that part.
Memory and large documents
Conversion runs entirely in your browser, one page after another. Each page is drawn on a canvas at the chosen resolution and encoded, and all finished images are kept in memory until you download them. A 100-page document at 3x can therefore need several hundred megabytes of memory, which older phones may not have.
If a large file stalls or the tab reloads, convert at 2x, or split the document into smaller parts and convert them separately. The file limit is 100 MB, one PDF at a time, and nothing is uploaded.