Benchmark: same 9.4 MB PDF (20-page scanned report)
- EazyAITools — 1.8 MB (81 % smaller). Browser-based, no upload.
- iLovePDF — 2.1 MB (78 % smaller). Server upload required.
- SmallPDF — 2.4 MB (74 % smaller). Free tier limited to 2 files/day.
- Adobe Acrobat online — 2.0 MB (79 % smaller). Free tier limited.
- Sejda — 1.9 MB (80 % smaller). 200 MB / day limit free.
- PDF24 — 2.2 MB (77 % smaller). Free desktop app available.
- Soda PDF online — 2.7 MB (71 % smaller). Account required.
How PDF compression works (so the numbers make sense)
Three operations shrink a PDF: downsampling embedded images (most savings; lossy), JPEG-recompressing images at a lower quality, and removing unused fonts/metadata/thumbnails. Text and vector content compress losslessly with flate/JBIG2 — barely shrinks because it was already small.
If your PDF is mostly text (e.g. a Word export), expect 20–40 % savings. If it's image-heavy (scans, photo report), expect 70–90 % savings. The same compressor will produce different ratios on different files.
Privacy: which tools upload your file
- EazyAITools — runs in browser, file never uploaded. Best for confidential PDFs.
- iLovePDF, SmallPDF, Adobe, Sejda, Soda — files uploaded to their servers, processed, deleted within 1–24 h per policy.
- PDF24 — desktop app is fully offline. Web version uploads.
Speed
- EazyAITools — 2–8 seconds for ≤10 MB files; slows on larger.
- iLovePDF — 4–10 seconds (server processing + upload/download round trip).
- Adobe Acrobat online — 6–12 seconds. Slowest of the lot.
Free-tier limits to know
- SmallPDF: 2 free tasks/day.
- iLovePDF: ≤5 files at a time on free.
- Sejda: 200 MB / day / 3 tasks/hour.
- Adobe: 2 free tasks/day after account login.
- EazyAITools: unlimited.
- PDF24 desktop: unlimited.
Which tool to pick — by job
- Confidential contract → EazyAITools or PDF24 desktop (no upload).
- Need maximum compression → EazyAITools or Sejda.
- Need merging + compression in one flow → iLovePDF.
- Need OCR + compression → Adobe Acrobat online.
- Volume compression for a business → PDF24 desktop or local Ghostscript.
Pro tips for maximum compression
- If the PDF is a scan of a black-and-white document, convert to greyscale before compressing — 30–40 % extra savings.
- Re-render to 150 DPI for screen-only PDFs (vs 300 DPI for print).
- Strip embedded fonts if you don't need exotic glyphs.
- Linearise (web-optimise) for faster first-page load.
FAQ
- Will compression damage text quality?
- No — text in PDFs is vector. Compression only affects embedded images.
- What's the lowest size I can achieve?
- Depends entirely on image content. A 100-page text-only PDF rarely goes below 200 KB; a heavily illustrated one may stay above 5 MB.
- Can I compress a password-protected PDF?
- Most tools refuse. Unlock it first using our Unlock PDF tool.
- Will the compressed PDF print at the same quality?
- If you compress for screen (150 DPI), printed quality drops. Compress for print (300 DPI) if you'll print.
- Why does my compressed file open slower?
- Some compressors disable web optimisation. Run 'linearise for fast web view' before saving the final.