How does this PDF compressor reduce file size?

It does two things. First it rebuilds the document using cross-reference object streams and drops bloated metadata, which alone shrinks PDFs that were never structurally compressed. Second, when image re-encoding is on, it decodes each embedded JPEG image, optionally downscales it to your chosen maximum dimension, and re-encodes it as a JPEG at the quality you set. The re-encoded images replace the originals in place, which is where the large savings come from.

Is my PDF uploaded to a server?

No. Everything runs in your browser using JavaScript and the canvas API. The file is read with the FileReader API, processed in memory, and offered back as a download. No bytes are ever sent over the network, so confidential contracts, scans and statements stay on your machine.

Why did my PDF not get smaller?

Some PDFs are already optimally compressed — for example exports from modern design tools or files that are mostly vector text. In that case re-saving cannot beat the original, so the tool tells you the original is your best version. Files full of high-resolution photo scans compress the most; pure text PDFs compress the least.

Will compressing reduce the quality of my PDF?

Text, vectors and layout are untouched and stay perfectly sharp. Only embedded raster images are re-encoded, and only if you keep image re-encoding switched on. Lowering the JPEG quality slider or the maximum image dimension trades visible image detail for a smaller file, so raise them if you need print-quality images.

What is the maximum image dimension setting for?

Phone-camera scans are often 4000 pixels wide — far more than a PDF page needs on screen or even in print. Capping the longest edge at, say, 2000 pixels downscales those oversized images before re-encoding, which can cut the file size dramatically with no visible difference at normal viewing or print sizes.

Can it compress password-protected PDFs?

No. A PDF that is encrypted with an open password cannot be read without that password, so the tool will report that the file could not be opened. Remove the password in your PDF viewer first, then compress the unlocked copy.

Does it work on phones and offline?

Yes. Because all processing is client-side it works in any modern mobile or desktop browser, and once the page has loaded it keeps working without an internet connection. Your last-used quality and downscaling settings are remembered in this browser for next time.

Compress PDF — Gera Tools

Compress PDF makes a PDF smaller without sending it anywhere. Drop in a file, choose how aggressively to squeeze it, and the tool reports the exact before and after size and the percentage saved before you download the result. It is built for the everyday problem of a PDF that is too big to email, too big for an upload limit, or simply heavier than it needs to be — scanned contracts, photo-laden reports, exported slide decks and image-heavy brochures.

How it works

The tool combines two independent, fully client-side strategies. The first is a structural re-save: the PDF is parsed and rewritten using cross-reference object streams, and bloated metadata such as stray author, title and keyword fields is stripped. Many PDFs — especially those produced by older or web-based exporters — were never structurally compressed, so this step alone can trim a noticeable slice off the file with zero effect on how it looks.

The second strategy, which you can toggle, is image re-encoding, and it is where the big numbers come from. Every embedded raster image in the document is decoded onto an off-screen canvas, optionally downscaled so its longest edge fits the maximum dimension you pick, and then re-encoded as a JPEG at your chosen quality. The fresh, smaller image bytes are slotted back into the document in place of the originals. Crucially, text and vector graphics are never touched — they stay perfectly crisp — so a text-heavy PDF keeps its sharpness while a scan-heavy PDF gets much lighter. After processing, the file is re-saved and handed to you as a download. If a re-encoded image would actually be larger than the original it is left alone, so you never end up worse off page by page.

Nothing is uploaded. The PDF is read locally with the browser’s FileReader, all work happens in memory, and the smaller file is produced as a download link. Your last quality and downscaling choices are remembered in this browser so repeat compressions are one click away.

Example

A 12-page scanned agreement exported at full phone-camera resolution weighs in at about 18 MB — far too large for most email attachment limits. Leaving image re-encoding on, setting the JPEG quality to 65%, and capping the longest image edge at 2000 px typically brings that down to roughly 2–3 MB, an 80–85% reduction, with the text still perfectly readable on screen and in print.

By contrast, a 40-page text-only report that was already well compressed might only shrink by a few percent — or not at all. In that case the tool tells you the original is already your best version rather than handing back a file that is no smaller. You always see the real before/after figures, so you can decide whether the trade-off is worth it, nudge the quality slider, and try again — all without the file ever leaving your device.