Compress PDF to 100 KB — free, no upload

How to use Compress PDF to 100 KB

1. Open your PDF in the tool. The Target size field shows 100 KB.
2. Keep If needed, convert pages to images to reach the size on, unless you must keep the text selectable.
3. For black text on white paper, tick Black and white (smaller for text documents).
4. Select Compress to 100 KB.
5. Read the result panel (new size, original size, percentage saved and method), then download the copy ending in -100kb.pdf.

What it does and when to use it

A 100 KB cap appears on many online application forms for supporting documents: a scanned ID card, front and back on one PDF, an address proof, a signed self-declaration, a birth certificate. It is tight, but unlike a 50 KB limit it leaves enough room for a clear page or two.

The tool exists so you do not have to guess settings. You set nothing except the target. It finds the highest quality that still fits under 100 KB, and it stops early if the file can get there without changing how the pages look.

Many PDFs saved straight from Word, Google Docs or a browser’s print dialog are already under 100 KB for a page or two. Scans are different. A phone scanner app or office copier stores each page as a large photo, so a single scanned page can easily be several hundred kilobytes or more. Those are the files this page is really for.

How it works

The PDF is opened and processed inside your browser. No server is involved.

First the tool checks the size. If the file is already at or below 100,000 bytes it returns it unchanged. Next it tries a lossless rebuild using pdf-lib and qpdf, which repack fonts, page descriptions and internal tables more efficiently. Nothing visible changes in this step.

If the file is still too big and image conversion is allowed, pdf.js renders every page and the tool saves each one as a JPEG inside a new PDF. It begins at 150 DPI, where an A4 page is about 1240 × 1754 pixels, and searches JPEG quality between 35% and 85%. When even 35% is too large, it lowers the resolution to the next step it predicts will fit (file size falls roughly with the square of the resolution) and searches again. The final file is the largest one that fits, which usually means the best looking one.

Worked examples

Front and back of an ID card on one page. A colour scan of this kind is often a few hundred kilobytes. The lossless pass changes little, so the tool renders the page and searches for a quality level that fits 100 KB. Because there is only one page, it can often stay at a fairly high resolution. Leave Black and white off here, since the photo and coloured background help the reviewer recognise the card.

A two-page signed declaration. Each page gets about 50,000 bytes. If the pages are black text on white paper, ticking Black and white usually lets the tool keep a higher resolution than it could in colour, so small print stays readable.

A text PDF from Word at 140 KB. Here the lossless rebuild may be all it takes. If so, the result says “Lossless rebuild”, the text stays selectable and the layout is identical.

Limits and tips

• Turning pages into images removes selectable text, clickable links and fillable fields. The tool warns you when it does this.
• If the target cannot be reached, the tool shows the smallest size it managed. Remove extra pages with Delete PDF Pages or choose fewer pages with the PDF Page Extractor, then try again.
• Scanning at a sensible setting in the first place helps. A phone scan of a text page does not need to be in full colour.
• If you need a searchable copy after compressing, run OCR PDF on the result; the file grows slightly because of the hidden text layer.
• Need even smaller? Compress PDF to 50 KB uses the same engine with half the budget. Have more room? Compress PDF to 200 KB keeps more detail.