pdfviz

Compress PDF
to 300 KB

or drop one here
Compression level
Target size
Choose a PDF file first.

Compressing a PDF to 300 KB means 307,200 bytes. It is the number exam boards and visa portals reach for most often, usually for a scanned certificate or an identity page. The bench ran 300 KB on a four-page mixed document and landed at 212.8 KB from 398.5 KB in all three runs. pdfviz runs entirely in your browser - your file is never uploaded, no account, no watermark - and every output is checked before download.

How to compress a PDF to 300 KB online

  1. Choose the PDF

    Press Choose a PDF, or drop the file on the page. The file is read in this browser tab and is not sent anywhere.

  2. The target is already set

    This page opens at 300 KB, so there is nothing to type. Pick a different level, or enter your own smaller number in KB, if you want another size.

  3. Press Compress

    Four methods race: copy the pages into a fresh file, re-encode the placed images, cut each embedded font down to the glyphs the pages draw, and, only when no other method reached the target, redraw the pages as images with the text kept on top.

  4. Read the check, then download

    Every candidate is opened again and its characters are counted against the source. The page shows the size, the method that won and the characters kept before it offers the download.

The four methods are described in full, with the measurements behind them, in how it works.

Where a 300 KB cap comes from

Government and examination upload fields are written for one scanned page, not for a document. 300 KB is roughly what a decent A4 scan costs at a quality where the print stays sharp. That is why the cap keeps turning up on forms that expect a certificate or an identity page. A free browser compressor covers one page like that without an account and without an upload.

If your file is a single scanned page, 300 KB is comfortable. The compress tool will usually get there through image quality alone and leave you a page that still reads cleanly at full zoom.

What the measured targets say about a 300 KB cap

The bench ran 300 KB on a four-page mixed document and landed at 212.8 KB from 398.5 KB. Reach climbs as the cap loosens, and kind matters more than the exact number.

Kind matters more than the exact number. Scans generally meet targets more often than long text exports. If your 300 KB file is a scan, the odds are good. If it is a long text export, expect to remove pages.

Where a 300 KB limit shows up in the real world

The 300 KB cap is the default on many exam board upload portals - including AQA and several Indian state examination boards - for scanned certificates and identity documents. The Schengen visa application portal uses 300 KB per document for supporting evidence, and a number of African government e-visa systems enforce the same cap. UK HMRC self-assessment uploads also sit at or near 300 KB for individual document submissions.

It is the number you hit when a form was built for one scanned A4 page at a readable quality, and nobody updated it. A single page scan at 300 KB will look sharp at full zoom. A four page scan at 300 KB gives each page 75 KB, which still holds printed text. A twenty page scan at 300 KB gives each page 15 KB, which does not.

A 200 KB target and a 400 KB target are the two next stops. The size breakdown tool shows where the bytes are going before you compress.

Multi page scans at a 300 KB target

Divide before you start. 300 KB across four pages is 75 KB per page, which still holds printed text. Across twenty pages it is 15 KB per page, which does not. If the form takes one file per document, split the scan and upload the parts.

A 200 KB target and a 400 KB target are the two next stops. Try the tighter one first if the form has ever bounced a file on you; forms that count kilobytes in thousands are stricter than they look.

Questions about compressing to 300 KB

How many bytes is a 300 KB limit?
307,200 bytes when a kilobyte is 1,024 bytes, which is how this tool counts. A form that counts in flat thousands caps you at 300,000, which is 7,200 bytes tighter. Target 290 KB if you have been refused once already.
Is 300 KB enough for a scanned certificate?
For one page, comfortably. The print stays sharp and a stamp or seal stays legible. The trouble starts at four or five pages, where the per page budget falls to a level that softens small type.
Why do exam portals ask for 300 KB?
The field was sized for one scanned A4 page at a readable quality, which is roughly what 300 KB buys. The cap is about storage per applicant, not about the document, so it rarely changes even when the requested document gets longer.
Was a 300 KB target measured on the public bench?
Yes. The bench ran 300 KB on a four-page mixed document and landed at 212.8 KB from 398.5 KB in all three runs.
Is my file uploaded to compress it to 300 KB?
No. pdfviz runs entirely in your browser via WebAssembly. The PDF is read from disk into memory, processed there, and written back to your downloads folder. Your PDF is sent nowhere; only anonymous usage counts leave the tab, and no account is needed.
Will a 300 KB target keep my text selectable?
In general, yes. Every candidate is read back before it ships, and any candidate that lost more than 2% of the non-space characters is refused.

The other pdfviz tools

They all run in a browser tab like this one. Each reads its own output back and checks it before offering the download, and none of them needs an account.