Tinker Tools

PDF Compressor Free & Private

Reduce your PDF file size instantly in the browser. All processing is done locally in your browser—your files are never uploaded to any server.

Compressor

Drop your PDF here

or click to browse files

How it works

1. Upload Your PDF

Drag and drop your PDF file onto the upload zone, or click to browse and select a file from your device.

100% Private

2. Automatic Compression

The tool automatically optimizes your PDF structure, removing unused objects and redundant data to reduce file size.

Instant Processing

3. Download Result

Review the compression results showing original vs. compressed size, then download your optimized PDF with one click.

No Quality Loss

What is PDF Compression?

PDF compression reduces the file size of a PDF document while preserving its visual quality and structural integrity. A PDF file is not a flat image — it is a container built from a hierarchy of objects. Each object can hold text, fonts, vector graphics, raster images, or metadata. These objects are linked together through a cross-reference table (xref) that maps byte offsets so a reader can jump to any object without scanning the entire file. When you compress a PDF, you are targeting these individual objects — shrinking embedded images, subsetting fonts, stripping orphaned objects, and rewriting streams with tighter encoding.

The internal structure matters because it dictates where the bulk of the file size lives. In a typical document-heavy PDF — say a 40-page report — text and vector graphics account for a surprisingly small fraction, often under 5% of the total size. Embedded images dominate. A single full-page photograph at 300 DPI can consume 3-5 MB as an uncompressed bitmap inside the PDF stream. Multiply that across a few pages and you get a 50 MB file that is painful to email or upload. Fonts come next. If the authoring tool embedded the entire typeface rather than subsetting it, you might carry 500 KB of glyph data for a font that only uses 60 characters in the document.

This tool compresses your PDF entirely inside your browser. The file never leaves your device — there is no server upload, no cloud processing, no third-party storage. The compression engine analyzes the PDF's object tree, identifies the largest targets, and applies a combination of image resampling, stream recompression, and metadata removal. You control the balance between file size and quality through a simple setting. The result is a smaller PDF that looks identical to the original on screen and in print, ready to share, archive, or upload to a portal with strict size limits.

Key Features and Benefits

  • Image resampling and recompression — Embedded images are the biggest contributors to PDF bloat. The compressor identifies raster images inside the PDF stream, downsamples them to a target resolution — typically 150 DPI for screen viewing or 200 DPI for print — and re-encodes them using JPEG or JPEG2000 compression. A 300 DPI image resampled to 150 DPI has one quarter the pixel count, which alone can cut its size by 70-80%. Combined with quality-aware JPEG encoding at level 75-85, you often see 90%+ reduction on image-heavy pages.
  • Font subsetting — When a PDF embeds an entire font file, it includes thousands of glyphs you will never see in the document. Font subsetting strips the unused glyphs and keeps only the characters that actually appear on the pages. A full copy of Noto Sans Regular weighs about 550 KB. After subsetting for a document that uses standard English text and punctuation, that drops to 30-50 KB. The visual output stays identical because every character the document references is still present.
  • Stream recompression with Flate — PDF content streams — the instructions that draw text and graphics on each page — can use various compression filters. Some authoring tools write streams with no compression or with inefficient LZW encoding. The compressor rewrites these streams using Flate (zlib/deflate) compression, which is universally supported by PDF readers and typically achieves 40-60% reduction on text-heavy streams. This is entirely lossless — the rendered output is bit-for-bit identical.
  • Metadata and dead object removal — PDFs accumulate invisible weight over time. Editing software often leaves behind orphaned objects, redundant XMP metadata blocks, embedded thumbnails, and document history. The compressor walks the object tree, identifies everything that is not referenced by the page tree or the catalog, and removes it. On a PDF that has been through several rounds of editing, this cleanup alone can trim 5-15% of the file size.
  • PDF/A compatibility mode — When you need to produce an archival-quality document, the compressor offers a PDF/A-aware mode that avoids stripping elements required by the ISO 19005 standard. It keeps the required XMP metadata, preserves ICC color profiles, and ensures fonts remain embedded after subsetting. You get a smaller file that still passes PDF/A validation — important for legal, government, and long-term archival workflows.
  • Privacy-first browser processing — The entire compression pipeline runs in your browser using JavaScript and WebAssembly. Your PDF is read from disk, processed in memory, and the result is written back to your downloads folder. No data leaves your machine at any point. This makes it safe for confidential contracts, medical records, financial statements, and any other document you would not want sitting on a third-party server.

How to Compress a PDF Online

  1. 1

    Upload your PDF

    Click the upload area or drag your file onto the page. The tool accepts PDF files up to 100 MB. It reads the file locally using the browser File API and parses the object tree to identify compressible elements. You will see a brief analysis showing the number of pages, embedded images, and fonts — this gives you a sense of where the file size is coming from before you even start compressing.

  2. 2

    Choose a compression level

    Select from three presets — low, medium, or high — or dial in a custom setting. Low compression keeps images at 200 DPI and JPEG quality 90, preserving near-original fidelity. Medium drops to 150 DPI and quality 80, which is the sweet spot for documents you will view on screen. High goes to 120 DPI and quality 65, aggressively shrinking the file for email attachments or web uploads where small size matters more than pin-sharp images.

  3. 3

    Toggle optional optimizations

    Enable or disable font subsetting, metadata removal, and dead object cleanup independently. If your document needs to stay PDF/A compliant, turn on the PDF/A mode toggle so the compressor preserves the required structural elements. For maximum compression with no constraints, leave everything on. Each toggle shows an estimate of how much additional space it will save.

  4. 4

    Review the compression results

    After processing, you see a side-by-side comparison of the original and compressed file sizes, the percentage saved, and a page-by-page preview. Scroll through the preview to check that images look acceptable, text is sharp, and nothing is missing. If the quality dropped too far, go back and raise the quality slider by 10-15 points. Most users find their ideal setting on the first or second try.

  5. 5

    Download the compressed PDF

    Click the download button to save the optimized file. The filename appends a suffix so you do not overwrite the original. If you compressed multiple PDFs in a batch, you get a zip archive containing all the optimized versions. The entire process — upload to download — typically takes under ten seconds for a 20-page document on a modern machine.

Expert Tips for PDF Compression

Understand the difference between lossy and lossless operations. Resampling images and re-encoding them at a lower JPEG quality is lossy — you lose pixel data that cannot be recovered. Font subsetting, stream recompression, and dead object removal are lossless — they discard nothing that affects the visual output. When you need to keep the document pixel-perfect, disable image resampling and rely on the lossless techniques alone. You will still get meaningful size reduction, typically 15-30%, without touching a single image.

Check image resolution against your actual use case. A PDF destined for a 4K desktop monitor needs at most 150 DPI for images to look crisp at 100% zoom. A PDF meant for offset printing at a commercial shop needs 300 DPI. If someone hands you a 300 DPI PDF and you are only emailing it, you can safely downsample to 150 DPI and cut the image payload by 75%. Going below 100 DPI for screen documents starts producing visible softness, so treat that as your floor.

Watch out for scanned documents. A 50-page scan from an office multifunction printer can easily hit 200 MB because every page is a full-resolution raster image. These PDFs benefit enormously from compression — dropping from 300 DPI to 150 DPI and applying JPEG quality 75 can shrink that 200 MB file to 15-20 MB. But always verify that the text in the scanned images remains legible after compression. If the document needs to go through OCR later, keep the DPI above 200 so the recognition engine has enough pixel data to work with.

Consider the cumulative effect of multiple optimization passes. Stripping metadata saves a few hundred kilobytes. Subsetting fonts saves a few hundred more. Removing dead objects trims another slice. None of these individually seem dramatic, but together they compound. On a moderately complex PDF with a dozen embedded fonts and several editing revisions, these lossless cleanups can remove 2-5 MB before you even touch the images. Run the lossless pass first, then decide if you need lossy image compression on top of it.

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PDF compression works best as part of a broader document workflow. If you are merging several PDFs into a single package, compress afterward — the merge process can introduce duplicate objects that the compressor will clean up. If you are converting from Word, the conversion engine may embed images at their original resolution, so a compression pass catches any oversized assets. And if you know certain images will end up in a PDF, compressing them beforehand with a dedicated image tool gives you finer control over per-image quality. Every step runs in your browser, so your documents stay private through the entire pipeline.

Frequently Asked Questions

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