What reaching 50 KB changes in a PDF

Set 50 KB as the target and the engine works down to it in steps, stopping at the first result that fits rather than padding the file back out.

It is the pictures inside the PDF that shrink: they are downsampled a step at a time until the file fits. Text typed into the document stays text while that is enough to reach the target. Ask for a size downsampling cannot reach and the pages are rendered to images instead, which makes the size but ends the text layer.

Files are processed on our servers, not in your browser. The upload and the result are both permanently deleted within 1 hour, no backups and no copies kept.

No watermark, and no account needed to use it. 2 files a day at up to 50 MB each, one at a time; signing in is free and raises each file to 100 MB.

Before you aim this low

1. 1

   Confirm the limit is real

   Fifty kilobytes is unusual enough to be worth reading twice. Make sure you have not misread 500 KB, and that the figure applies to the one file you are uploading rather than to the full set of attachments.

2. 2

   Look at what you already have

   A text document needs nothing from this page. Ten pages of plain typed matter occupy 19 KB untouched, so open the file properties before compressing and you may find you are already finished.

3. 3

   Trim the document, not the quality

   If the file is a scan, removing pages gets you further than any target will. Upload only the page the form actually asked for, and that page has the entire 50 KB rather than a slice of it.

A target most documents should not be given

50 KB is a severe ask of a PDF. Two kinds of file manage it honestly: documents that are nothing but typed text, and a single scanned signature or set of initials. Everything else either misses the number or arrives in a state nobody wants to read. If a form has handed you this figure, work through what follows before you upload anything.

What genuinely fits in 50 KB

Two things. Documents whose content is typed characters, which cost almost nothing to store and often sit under 20 KB with no help at all. And one scanned page carrying a signature, initials or a short handwritten note, where there is very little ink and a great deal of blank paper.

A three-page colour scan does technically reach 44 KB at this target, which looks like a success until you open it. The pages are all there and the layout holds, but small print has stopped being something you read comfortably on a screen. If someone at the other end has to study the document rather than confirm it exists, 44 KB is not enough.

When to walk away from this target

Use 100 KB if the scan has to stay legible. That is the lowest point at which a full page of scanned text remains comfortable to read, and the same three-page scan arrives at 96 KB there with its wording clear. The extra fifty kilobytes buys more than the number suggests.

And if nothing is forcing a limit on you at all, do not compress to a tiny figure for its own sake. There is no reward for a small file beyond getting past whatever is checking it, and a document that has to be scanned again because nobody can read it costs far more than the kilobytes you saved.

Why colour scans resist 50 KB

A scanner does not record your document, it photographs it. Every page becomes an image, and images are where almost all of a PDF's weight lives, typically 70 to 95 per cent of it. Three colour pages at scanning resolution is several megabytes of picture data that somehow has to end up in 50 KB.

Colour is the cheapest thing to surrender. Scanning again in greyscale throws away two thirds of the colour information up front, before quality has to suffer at all, and a form, a certificate or a letter carries no meaning in its colour anyway. After that, scan at 150 dots per inch instead of 300 and put fewer pages in each file.

Frequently asked questions