Compress PDF files online for free. Reduce PDF file size by rasterizing pages at optimized quality — entirely in your browser, no upload, no server, 100% private.
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PDF files only — processed entirely in your browser
Best quality, moderate size reduction (~30–50%)
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PDF Compressor is a free, browser-based tool that reduces PDF file sizes by re-rendering each page at an optimized resolution and re-encoding the content as compressed JPEG images. The entire process runs locally in your browser using PDF.js for parsing and jsPDF for reconstruction — no files are ever uploaded to any server, making this tool completely safe for confidential documents including legal contracts, financial statements, medical records, and personal files. Unlike cloud-based PDF compressors (iLovePDF, SmallPDF, Adobe), your data never leaves your device.
High Quality (150 DPI, 85% JPEG) — Best for documents that will be printed or where text readability is critical. Minimal visible quality loss. Suitable for business documents, contracts, and reports.
Balanced (120 DPI, 70% JPEG) — Recommended default. Good balance between file size and readability. Ideal for email attachments, web uploads, and general sharing. Text remains fully legible.
Small Size (96 DPI, 55% JPEG) — Prioritizes file size reduction. Some softening of fine text and image details. Best for archiving scanned documents, reducing storage costs, and uploading to platforms with size limits.
Maximum Compression (72 DPI, 35% JPEG) — Aggressive compression for minimum file size. Visible quality loss on detailed images and fine text. Use only when file size is the primary constraint (e.g., email attachment limits, form upload limits).
Compression effectiveness depends heavily on PDF content type. Scanned documents and photo-heavy PDFs (invoices, receipts, printed forms) typically achieve 60–85% size reduction because they consist primarily of raster images that benefit greatly from JPEG re-encoding. Mixed-content PDFs (presentations, reports with images) achieve 40–65% reduction. Text-heavy PDFs with vector graphics (academic papers, technical documentation) achieve 20–40% reduction — in some cases, the compressed file may be larger than the original if the PDF was already well-optimized. For vector-only PDFs, dedicated tools like Ghostscript are more appropriate.
Essential terms and definitions related to PDF Compressor.
A file format developed by Adobe that preserves document layout, fonts, images, and formatting regardless of the viewing software or device. PDFs can contain vector graphics (scalable, sharp at any size), raster images (pixel-based, quality depends on resolution), and embedded fonts. Document compression strategies differ based on whether content is primarily vector or raster.
A measure of image resolution indicating how many pixels are packed per inch. For screen display, 72–96 DPI is standard. For professional printing, 300 DPI is the industry standard. Reducing the DPI during PDF compression reduces the number of pixels per page, directly reducing file size. A 150 DPI page has 56% fewer pixels than a 200 DPI page of the same dimensions.
A value (typically 1–100) controlling the aggressiveness of JPEG lossy compression. Higher values preserve more image data and produce larger files; lower values discard more data for smaller files. JPEG compression works by approximating image blocks using frequency components (DCT), discarding high-frequency details that the eye is less sensitive to. Quality 85 is generally imperceptible to human vision; below 50 produces visible compression artifacts.
No. The entire compression process happens in your browser using PDF.js and jsPDF. Your PDF file is never transmitted to any server. This makes the tool completely safe for confidential documents — legal contracts, financial statements, medical records, and personal documents can all be compressed without privacy concerns.
The tool loads your PDF using PDF.js, renders each page to an HTML Canvas element at the target resolution and quality, then reconstructs the pages into a new PDF using jsPDF. The main compression gain comes from re-encoding page content as JPEG at a lower quality factor and reducing the render resolution (DPI). This approach works best for PDFs containing images or scanned documents.
Compression results depend heavily on the PDF content. Image-heavy PDFs and scanned documents typically achieve 60–85% size reduction at Medium quality. PDFs containing mostly text and vector graphics may achieve 20–40% reduction. High compression with very aggressive settings can produce 90%+ reduction but at reduced visual quality. Use the quality slider to find the best size/quality balance for your use case.
Yes, to varying degrees. At High quality (75–90), text remains highly readable. At Medium quality (40–70), fine text may soften slightly. At Low quality (below 40), text can become noticeably blurry — not recommended for documents with small fonts. The compression process rasterizes pages, which means text is converted to image data and loses its vector sharpness. For print-quality documents, use High quality.
This can happen with PDFs that are already well-optimized, contain mostly vector text and graphics (no raster images), or were created with very efficient compression. In these cases, rasterizing and re-encoding adds overhead rather than reducing it. Very small PDFs (under 100 KB) often cannot be compressed further. For vector-only PDFs, dedicated PDF optimization tools like Ghostscript may perform better than image-based compression.
Common errors developers encounter and how to resolve them.
PDF fails to load or shows blank pages Ensure the file is a valid PDF (not a renamed image or document). Password-protected PDFs cannot be loaded — remove the password protection first. Very large PDFs (100+ pages or 100+ MB) may exceed browser memory limits; try splitting the PDF into smaller segments first using an offline tool.
Compression takes a very long time High-resolution PDFs with many pages are computationally intensive to rasterize in the browser. Try reducing the target DPI to 96 or 72 in the settings, or use the "First 10 pages" option to compress a subset. Closing other browser tabs frees memory and speeds processing. Modern browsers (Chrome/Edge) handle large PDFs significantly faster than others.
Text is blurry in the compressed PDF Increase the quality slider to 80% or higher. For documents where text clarity is critical, use the "High quality" preset which renders at 150 DPI with 85% JPEG quality — this balances file size reduction with readable text. If text blurriness is unacceptable, the original PDF may already be using vector text that cannot be compressed further without quality loss.