Compress PDF
— No Upload
Drop a PDF, dial in quality or set a target size, and shrink it right in your browser. Works best on scanned & image-heavy PDFs.
No upload
100% private
No sign-up
Grayscale & target size
1 — Choose your PDF
Click to browse or drag a PDF here
Change file
2 — Compression settings
Screen
72 DPI · JPEG 35%
E-mail / web only
eBook
110 DPI · JPEG 60%
Balanced default
Print
150 DPI · JPEG 78%
Keep print quality
Heads-up: Pages are re-rendered as JPEG images, so text becomes a picture — no longer selectable or searchable. Best for scanned documents, photos, and image-heavy PDFs. For text-only PDFs, gains are limited.
3 — Compress
Preparing…
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Original
→
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Compressed
How it works
Everything runs inside your browser tab using two open-source libraries. No server involved — close the tab and the file is gone.
1 — Render pages (pdf.js)
Each page is drawn onto an off-screen canvas at your chosen DPI. Vector content, fonts, and images all become a flat raster bitmap.
2 — Optional grayscale
If Grayscale is on, the canvas pixels are desaturated (weighted luminance formula) before encoding. This removes all colour data, which can cut 20–60% off photos and coloured scans.
3 — Encode as JPEG (Canvas API)
Each canvas is exported as a JPEG at your chosen quality. JPEG is highly efficient for photos and scans — this is where most size savings come from.
4 — Rebuild & download (pdf-lib)
Each JPEG is embedded into a fresh PDF at the original page dimensions. For Target Size mode, the quality is tuned across up to 4 passes until the output meets your goal.
Tips: Still too large? Try Grayscale — it often saves more than lowering JPEG quality. For email attachments, Screen preset + Grayscale usually hits under 1 MB. For print, keep DPI ≥ 150 and JPEG ≥ 70%.
Frequently asked questions
Is my PDF uploaded anywhere?▼
No. The file is read directly into your browser's memory using the JavaScript File API. All rendering, grayscale conversion, JPEG encoding, and PDF reconstruction happen locally in your tab. Nothing is transmitted to any server — you can even use this tool offline once the page has loaded.
What types of PDF compress the most?▼
Scanned documents, photo-heavy brochures, and PDFs exported from image editors typically shrink 50–90%. These are already made of images, so re-encoding as JPEG removes a lot of redundant data. Enabling Grayscale on colour scans or coloured pages saves an extra 20–60% on top of that. Plain text-only PDFs may actually get larger, because crisp vector text replaced by a JPEG image needs more bytes.
What does the Grayscale option do?▼
Before encoding each page as JPEG, the tool converts every pixel to greyscale using a standard luminance formula (0.299 R + 0.587 G + 0.114 B). This strips all colour information from the image data. Greyscale JPEGs compress significantly better because JPEG's colour (chroma) channels can be discarded. Use it for scans, contracts, and receipts where colour is not needed.
How does Target Size mode work?▼
You enter the maximum file size you want (in MB or KB). The tool makes an initial compress pass, measures the result, then adjusts JPEG quality up or down and tries again — up to 4 passes. It converges on a quality setting that gets as close as possible to your target. Very small targets (e.g., under 200 KB for a multi-page scanned PDF) may produce visibly blurry pages, since there is a physical limit to how much quality can be reduced.
Will text still be selectable after compression?▼
No. Because every page is re-rendered as a raster image, any selectable or searchable text layer is flattened into pixels. If you need to preserve searchable text, this compressor is not the right tool. Use it for scans, receipts, and visual documents where text selection doesn't matter.
Why did my compressed file end up larger?▼
This happens when the original PDF contained highly optimised vector text or already-compressed images. Re-rendering crisp text as a high-resolution JPEG image takes more bytes than the original vector representation. To fix it: lower the DPI slider, lower the JPEG quality, or enable Grayscale. If the file is already well-optimised text, this tool may not help — try a tool that removes metadata or compresses object streams instead.
How large a PDF can I process?▼
Because everything runs in the browser, the practical limit is your device's RAM. Hundreds of pages of scanned documents are typically fine on a modern laptop or desktop. Very large files (1,000+ pages or several hundred MB) may be slow or run out of memory. In that case, use the Page Range option to compress sections, or split the file first. The tool frees each rendered page from memory immediately after encoding it to keep usage as low as possible.