How does browser-based Ghostscript compression work?

Ghostscript has been compiled to WebAssembly (WASM), which lets it run natively inside any modern browser. Your PDF is processed by the actual Ghostscript engine without any server involved.

Does this preserve text and vector quality?

Yes. Unlike canvas-rasterization approaches, Ghostscript recompresses embedded images while keeping text, fonts, and vector graphics as real PDF objects. Your text stays sharp and selectable.

What do the quality presets mean?

Screen (72 dpi) is for email and on-screen viewing. eBook (150 dpi) balances quality and size. Printer (300 dpi) is for desktop printing. Prepress (300 dpi+) is for professional commercial printing.

How much will my PDF shrink?

Results depend on content. Image-heavy PDFs typically shrink 50-85% on the eBook preset. Text-only PDFs compress less (10-30%) since text is already compact in PDF format.

Will the compressed PDF have a watermark?

No. Zero watermarks, logos, or branding are ever added. You receive a clean, professional PDF identical in appearance to your original.

Compress PDF Online Free – Real Ghostscript Engine, No Uploads

Loading Ghostscript engine (~16 MB, cached after first use)…

Drop your PDF here to compress

Ghostscript recompresses images, preserves text & vectors — no rasterization

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— — pages

Compression Quality

Choose a Ghostscript preset

📱

Screen

Smallest file

72 dpi

📖

eBook

Best balance

150 dpi

🖨️

Printer

Home/office

300 dpi

🎨

Prepress

Pro printing

300 dpi+

eBook — Ghostscript compresses images to 150 dpi. Ideal for tablets, general reading, and balanced file sharing. Typical reduction: 40–70%.

Initialising…

① Load engine ② Read file ③ Compress ④ Finalise

Compression Complete!

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Original

—

Compressed

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Saved

File size reduction0%

How to Compress a PDF Online

Three steps. No account. No uploads. Completely free.

Upload Your PDF

Drag and drop your PDF or click Select PDF File. Your file stays on your device — Ghostscript WASM loads into your browser's memory and processes it locally.

Choose a Preset

Select Screen for email, eBook for balance, Printer for desktop printing, or Prepress for professional print. Each maps to a real Ghostscript -dPDFSETTINGS profile.

Compress & Download

Click Compress PDF. Ghostscript runs its pdfwrite device in WASM — recompressing images, optimising streams, and preserving all text and vector content exactly.

Why QwikCompress Is Different

Most browser PDF compressors rasterize everything into blurry images. This one does not.

Real Ghostscript, Not Canvas

Other tools render every page as a JPEG — destroying text quality. Ghostscript recompresses only embedded images, leaving text, fonts, and vectors fully intact as proper PDF objects.

100% Private

Your PDF is never sent anywhere. Ghostscript WebAssembly runs inside your browser tab — no server sees your file, not even for a millisecond.

Text Stays Selectable

Because Ghostscript works at the PDF stream level, your text remains copy-paste-able and searchable after compression. No OCR re-run needed.

Standard GS Presets

Screen, eBook, Printer, and Prepress map directly to Ghostscript's -dPDFSETTINGS flags — the same parameters used by print professionals and Linux sysadmins for decades.

No Watermarks, Ever

Zero logos, stamps, or branding added at any step. The file you download is completely clean — what goes in is what comes out, just smaller.

Works on Any Device

Runs in Chrome, Safari, Firefox, and Edge on Windows, Mac, iPhone, and Android. The WASM binary is downloaded once and cached by your browser for instant future use.

Ghostscript Compression Presets Explained

Each preset is a native Ghostscript -dPDFSETTINGS profile — not a custom approximation.

Preset	GS Flag	Image DPI	Best For	Typical Reduction
📱 Screen	`/screen`	72 dpi	Email, web, on-screen	60–85%
📖 eBook	`/ebook`	150 dpi	Tablets, general sharing	40–70%
🖨️ Printer	`/printer`	300 dpi	Home/office printing	20–45%
🎨 Prepress	`/prepress`	300 dpi+	Commercial print	10–30%

When to Use PDF Compression

Everyday situations where file size limits get in the way.

📧 Email Attachments

Most email providers cap attachments at 10–25 MB. Compress reports or brochures to ensure they send without being rejected or bouncing.

🏛️ Government Portals

Many government and court portals enforce strict upload limits of 2–5 MB. Compress your PDF to exactly meet the size before submitting.

🎓 University Submissions

Thesis repositories and LMS systems often have upload caps. Compress dissertations and coursework to size before the deadline.

📱 Mobile Sharing

Sharing PDFs via WhatsApp, Telegram, or iMessage is faster and more reliable with smaller files on mobile data connections.

☁️ Cloud Storage

Make the most of free storage tiers on Google Drive, Dropbox, or OneDrive without upgrading to a paid plan.

🌐 Website Uploads

CMS platforms like WordPress have upload limits. Compress PDFs used as downloadable brochures or whitepapers before uploading.

Frequently Asked Questions

Technical details and common questions about this PDF compressor.

How does Ghostscript WASM compression work in a browser?

Ghostscript — a C PDF processing engine that has existed since the 1980s — has been compiled to WebAssembly using Emscripten. The full real Ghostscript binary runs inside your browser tab. Your PDF is written to an in-memory virtual filesystem, Ghostscript processes it using its pdfwrite device, and the output is read back and downloaded to your device. No server is involved at any step.

Why is Ghostscript better than canvas-based compression?

Canvas-based compressors render every page to a bitmap and reassemble them into a PDF. This converts all text and vector graphics into blurry pixels — the result is not selectable, not searchable, and looks poor when zoomed. Ghostscript works at the stream level: it recompresses only embedded raster images, while keeping all text, fonts, and vector content as proper PDF objects.

Are my files uploaded to a server?

No. The Ghostscript WASM binary (~16 MB) is loaded from a CDN once and runs entirely inside your browser. Your PDF file itself never leaves your device — it is read into browser memory, processed locally by the WASM engine, and the output is downloaded directly. No network request is made with your file content.

Why does the first compression take longer?

The Ghostscript WebAssembly binary is approximately 16 MB. Your browser downloads and compiles it the first time. Subsequent uses in the same session reuse the loaded engine instantly. Your browser also caches the WASM file, so future visits are much faster.

Will compressed PDFs have a watermark?

No. Ghostscript does not add watermarks or branding. The library is open source (AGPL-3.0) and this tool is free — there is no reason to watermark your output. You receive a completely clean compressed PDF.

Which preset should I use?

For email and general web sharing, use eBook — best balance of quality and compression. For maximum size reduction (strict upload limits), use Screen. For printing at home or the office, use Printer. For PDFs going to a commercial print house, use Prepress.

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