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.
How to read compression-tool comparisons honestly
Every tool publishes flattering reduction percentages, but the comparison only matters at equal visual quality. A tool that crushes a 10MB PDF to 1MB sounds great until you discover it downsampled images to 72 DPI and the result is unusable for print. Always compare at the same output DPI and the same JPEG quality, and judge by file size for that fixed quality, not by raw percentage. The right tool depends on the input — image-heavy scans favour MRC (mixed raster content) compressors, text-heavy PDFs favour object stream optimisation.
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.