To compress a PDF, you re-encode the images embedded inside it at a lower resolution and quality — this is where almost all of a PDF's file size comes from. A browser-based compressor does this entirely on your device, with no file upload, in under a minute for most documents.
Free PDF Compressor — runs in your browser
No uploads. No account. Your file never leaves your device.
Compress PDF nowWhy is your PDF so large?
The vast majority of PDF file size comes from embedded images. When you scan a document, each page is stored as a full raster image — often at 200 to 300 DPI — inside the PDF. When you export a report from Word or PowerPoint, every photo and chart is embedded at its original resolution. A 20-page PDF with scanned receipts can easily reach 30–50 MB, while the same document as typed text would be under 200 KB.
Beyond images, PDFs can also carry:
- Embedded fonts — the full font files are often included, not just the characters used
- Hidden revision history — some editors (Word, LibreOffice) leave undo data inside exported PDFs
- ICC color profiles — used for professional print workflows, unnecessary for screen viewing
- Page thumbnails — preview images generated by the software that created the PDF
- JavaScript and form field data — especially in interactive PDFs from Adobe tools
Compression tools address all of these, but the images are where you get the biggest gains — typically 40–70% size reduction on image-heavy PDFs.
The problem with most online PDF compressors
When you use iLovePDF, Smallpdf, Adobe Acrobat online, or most other web-based tools, your file is uploaded to their servers to be processed. For a photo of your cat, this is irrelevant. For a pay stub, tax return, bank statement, rental contract, or medical record — it is a meaningful risk.
These companies have privacy policies and deletion timelines (often 1–24 hours), but your file still travels over the internet and sits on hardware you do not control. Data breaches happen. Legal requests happen. Accidental retention happens.
The better alternative is client-side compression — where the processing happens entirely inside your browser using JavaScript. The file never leaves your device. There is nothing to breach, nothing to retain, nothing to intercept. This is how FixMyPDF works.
How to compress a PDF step by step
This takes under two minutes for most files:
-
1
Open the PDF Compressor
Go to fixmypdf.tech/tools/compress.html. No sign-up, no download. -
2
Drop or select your PDF
Drag your file onto the drop zone or click to browse. The file loads locally in your browser. -
3
Choose a compression level
Pick Standard, High, or Maximum — or switch to Target Size mode and type an exact target in MB. More on each level below. -
4
Click Compress PDF
The tool scans every embedded image, re-encodes it at the chosen quality and resolution, and rebuilds the PDF. For a 10 MB file this typically takes 5–15 seconds. -
5
Download your compressed file
Click Download. Your original file is untouched — the compressed version is saved separately to your device.
Understanding the three compression levels
The compressor works by reducing image dimensions (resolution) and JPEG encoding quality. Resolution does most of the heavy lifting — quality is kept as high as possible at each level (never below 65% JPEG quality).
| Level | Image resolution | Best for | Expected reduction |
|---|---|---|---|
| Standard | ~150 DPI | Email, screen sharing, archiving with quality preserved | 20–40% smaller |
| High | ~100 DPI | Web uploads, form submissions with a file size cap | 40–60% smaller |
| Maximum | ~72 DPI | Messaging apps, getting under a strict limit (e.g. 5 MB) | 55–75% smaller |
| Target Size | Adaptive | When you know the exact limit (e.g. 2 MB form cap) | Hits your target or gets as close as possible |
Target Size mode is worth knowing about. Instead of picking a level, you type a target — say, 3 MB. The tool runs a binary search on image resolution first, then adjusts quality if resolution alone is not enough. It stops the moment it hits your target. This is ideal when you are dealing with a government form or HR portal that has an exact upload cap.
How much smaller will your PDF get?
Results vary significantly depending on what your PDF contains. Here is a realistic breakdown based on common document types:
| PDF type | Standard | High | Maximum |
|---|---|---|---|
| Scanned document (photos of pages) | 30–50% | 50–65% | 65–75% |
| Photo-heavy report or presentation | 25–45% | 45–60% | 60–70% |
| Mixed (text + some images) | 15–30% | 30–50% | 50–65% |
| Text-only PDF (no embedded images) | 5–15% | 5–15% | 5–15% |
If your PDF is text-only, do not expect dramatic results from any browser-based compressor — including Ghostscript-based server tools. The text stream is already compact. The gains you do see come from stripping metadata, thumbnails, and unused embedded font subsets.
Does compressing a PDF reduce quality?
The honest answer: it depends entirely on what is in your PDF.
Text, headings, and vector graphics (logos, diagrams created in Illustrator or Inkscape) are stored as scalable instructions, not pixels. Compression does not touch them. They remain perfectly sharp at every compression level, at every zoom level, at any print size.
Raster images (photos, scanned pages, screenshots) are stored as pixel grids. The compressor reduces their resolution and re-encodes them as JPEG. At Standard level the difference is usually invisible on screen. At Maximum level, zooming in on a photo will reveal some softness, and fine detail in scanned handwriting can become slightly less crisp.
For documents you will print professionally — a brochure, a large-format poster — do not compress. For everything else: email attachments, web uploads, documents read on screen, sharing over WhatsApp — Standard or High compression is invisible in everyday use.
One important guarantee: the compressor never reduces JPEG quality below 65%. Below that threshold JPEG artifacts become clearly visible. The tool will reach the smallest file it can while staying above this floor.
Tips to get the smallest possible file
1. Remove pages you do not need first
If your PDF has 40 pages but you only need 10, remove the unused pages before compressing. Fewer pages means fewer images to process, and the result will be dramatically smaller. This is the single most effective thing you can do before running compression.
2. Compress before merging, not after
If you need to merge multiple PDFs, compress each one individually first, then merge the compressed versions. Compressing a merged 80-page document is slower and gives the tool less room to optimise per-image.
3. Re-export from the source if possible
If the PDF was exported from Word, PowerPoint, or Google Docs, re-export it with lower image quality settings before compressing. Word's "Minimum size (publishing online)" export option can halve the file size before you even open a compressor. Compressing an already-optimised export gives better results than trying to compress a raw high-resolution export.
4. Use Target Size mode for strict upload limits
Government portals, HR systems, and university submission forms often have exact file size caps — 2 MB, 5 MB, 10 MB. Instead of guessing which compression level hits the limit, use Target Size mode and type the exact cap. The tool will binary-search its way to your target automatically.
5. Split a large PDF before compressing on older devices
If you are on an older phone or laptop and have a very large PDF (50 MB+), split it into smaller chunks first. Processing happens in your browser's memory, and splitting reduces peak RAM usage significantly. Compress each chunk, then merge the results.