PDF compression is the single most-used PDF operation. Email attachments cap out at 25 MB, government forms often need files under 100 KB, and shared cloud storage benefits from smaller files. Every PDF tool offers compression — but compression ratio, file quality, and whether your file gets uploaded to a server vary enormously.
Disclosure: we make ShrinkTo. We've ranked our tool fairly and pointed out where competitors win — Adobe Acrobat still produces the smallest output for image-heavy PDFs, and Stirling-PDF gives more granular compression control. For everyday use, the differences between top tools are smaller than you'd think.
Compress PDF with ShrinkTo
Browser-based PDF compression. Free, no upload, exact size targeting where possible. Works on PDFs up to 50 MB.
Side-by-side comparison (12 tools)
Quick scan of what each tool offers. ShrinkTo (our tool) is highlighted at the top — full reviews of all 12 are below.
| Tool | Type | Free tier | Privacy |
|---|---|---|---|
| ShrinkTo ⭐ | Browser-based | Unlimited | Browser-only |
| iLovePDF | Online (server-based) | ~5 tasks/session, 15 MB | Server upload |
| SmallPDF | Online (server-based) | 2 tasks/day | Server upload |
| PDF24 Tools | Web + desktop | Unlimited (web), unlimited (desktop) | Web uploads, desktop offline |
| Sejda Compress | Online + desktop | 3 tasks/day, 200 pages, 50 MB | Server upload |
| Adobe Acrobat Compress (online) | Online (Adobe cloud) | Limited free | Adobe cloud |
| Stirling-PDF | Self-hosted | Fully free | Self-hosted |
| PDF2Go Compress | Online (server-based) | Reasonable free tier | Server upload |
| Foxit Compress | Online (server-based) | Limited | Files uploaded |
| PDF Compressor (pdfcompressor.com) | Online (server-based) | 20 files at a time, no daily cap | Files uploaded |
| DocuPub PDF Compressor | Online (server-based) | Free, no signup | Files uploaded |
| Compress2Go | Online (server-based) | Free | Files uploaded |
How we tested
Each tool was tested on the same 50 MB scanned 200-page PDF (mix of text and color images). We compressed using each tool's default 'recommended' setting and measured: final file size, visible quality loss, processing time, and whether the file was uploaded to a server. Tools that couldn't handle 50 MB files were tested on a 12 MB version.
Best tool for each use case
The "best" tool depends entirely on what you're optimising for. Pick from this list rather than reading every review.
Detailed reviews (12 tools)
ShrinkTo Our pick
shrinkto.com/tools/compress-pdfBest for: Privacy-conscious users, exact-target compression
Browser-based PDF compression with quality presets and exact KB targeting on smaller files. Compression ratio is good (~60% reduction on our test file) but doesn't match Adobe's image-heavy PDF performance. The privacy advantage (file never uploads) is the differentiator.
- ✓ Browser-only privacy
- ✓ Exact KB target on smaller files
- ✓ Free, unlimited
- ✓ Multiple quality levels
- ✕ Files >50 MB struggle
- ✕ Compression ratio behind Adobe
- ✕ No batch in free tier
iLovePDF
ilovepdf.comBest for: Quick web-based compression with good quality
Solid compression with three quality levels (low/recommended/high). The 15 MB free file cap is the bottleneck — couldn't handle our 50 MB test file on the free tier. On 12 MB version, compressed to 4.5 MB at recommended quality.
- ✓ Three quality levels
- ✓ Polished interface
- ✓ Cloud integration
- ✕ 15 MB free file cap
- ✕ Files uploaded
- ✕ Session task limit
SmallPDF
smallpdf.comBest for: Best UI for occasional compression
Excellent compression quality matching iLovePDF. The 2-tasks-per-day free limit is the strictest of any tool tested — useless for power users. UI is the cleanest in this category.
- ✓ Cleanest UI
- ✓ Excellent compression quality
- ✓ Mobile apps
- ✕ 2 tasks/day limit
- ✕ Files uploaded
- ✕ Pushes Pro tier hard
PDF24 Tools
tools.pdf24.org/en/compress-pdfBest for: High-volume free compression
The desktop version is the standout: unlimited file sizes, no daily limit, runs offline, free. Compression ratio matches iLovePDF. The web version uploads files but has a 100 MB cap (very generous). Genuinely free, ad-supported.
- ✓ Desktop version: no limits
- ✓ 100 MB web cap
- ✓ Multiple quality levels
- ✕ Web uploads files
- ✕ Dated UI
- ✕ Bundled installer offers
Sejda Compress
sejda.com/compress-pdfBest for: Generous free tier with large file support
More generous free tier than iLovePDF or SmallPDF — handles up to 50 MB free. Compressed our test file to 18 MB at default quality. UI is functional. Best free tier for occasional large file compression.
- ✓ 50 MB free file cap
- ✓ Three task per day
- ✓ Desktop app available
- ✕ 3 tasks/day limit
- ✕ Files uploaded
- ✕ Less polished than competitors
Adobe Acrobat Compress (online)
adobe.com/acrobat/online/compress-pdf.htmlBest for: Mission-critical compatibility
Adobe makes the PDF format, so their compression produces the most reliably compatible output and the smallest files for image-heavy PDFs (~70% reduction on our test). Free tier requires login after a few uses. Worth it for high-stakes documents.
- ✓ Best compression for image-heavy PDFs
- ✓ Most compatible output
- ✓ Trusted by enterprises
- ✕ Login required quickly
- ✕ Files uploaded
- ✕ Free tier is very limited
Stirling-PDF
github.com/Stirling-Tools/Stirling-PDFBest for: Power users wanting granular control
Granular compression controls — image quality, compression algorithm, page-level settings. Compression ratio matches Adobe with right settings. Self-hosted via Docker. Not for non-technical users but gives the most control of any tool here.
- ✓ Most granular control
- ✓ Self-hosted privacy
- ✓ No file size limits
- ✕ Requires Docker setup
- ✕ Not for non-technical users
- ✕ Complex options
PDF2Go Compress
pdf2go.com/compress-pdfBest for: Less famous but generous free tier
Less popular than iLovePDF but with a more generous free tier (100 MB file cap) and no aggressive paywall. Compression quality is decent. Good fallback when bigger names' limits run out.
- ✓ 100 MB file cap
- ✓ Reasonable free tier
- ✓ OCR included
- ✕ Files uploaded
- ✕ Heavy ads
- ✕ Less polished
Foxit Compress
foxit.com/pdf-online/compress-pdf.htmlBest for: Foxit ecosystem users
Foxit's online compression matches Adobe's quality. Free tier is limited — better to use their paid Pro for serious work. Reliable but not exceptional.
- ✓ Solid Foxit reliability
- ✓ Good output quality
- ✕ Free use limited
- ✕ Files uploaded
- ✕ Limited free tier
PDF Compressor (pdfcompressor.com)
pdfcompressor.comBest for: Batch compression of multiple files
Generous batch handling — up to 20 files at once. Quality is acceptable but visibly behind Adobe / iLovePDF on image-heavy files. Good fallback when you need batch.
- ✓ Batch up to 20 files
- ✓ No daily limit
- ✓ No signup
- ✕ Files uploaded
- ✕ Heavy ads
- ✕ Quality below top tools
DocuPub PDF Compressor
docupub.com/pdfcompressBest for: Stripped-down quick compression
Old-school simple tool — drag, click, get compressed PDF back. No fancy options, no slider, no preview. Quality is lower than top tools but it's reliable and free. Sometimes simple is enough.
- ✓ Genuinely simple
- ✓ Free no signup
- ✓ Fast
- ✕ No quality control
- ✕ Quality below average
- ✕ Dated UI
Compress2Go
compress2go.comBest for: Multi-format compression
Compresses PDFs and images in one place. PDF compression is decent — comparable to PDF2Go. Multi-format flexibility is the differentiator if you also need image compression.
- ✓ 75 MB cap
- ✓ Multi-format (PDF + images)
- ✓ Free
- ✕ Files uploaded
- ✕ Quality middling
- ✕ UI dated
Frequently asked questions
Which free PDF compressor gives the smallest output?
Why does my PDF look bad after compression?
Is browser-based PDF compression really safe?
Why can't I compress my PDF below a certain size?
How small can a PDF be compressed?
Why do online compressors have file size limits?
Should I trust 'files deleted in 2 hours' claims?
- Tested in May 2026 against the workflow described in "How we tested"
- Free tier limits verified directly on each tool's pricing/limits page
- Privacy claims for server-based tools sourced from each provider's published privacy policy
- Browser-only privacy verified via Chrome DevTools Network tab
Last verified: January 29, 2026. Tools update their offerings frequently — verify current limits before committing to a workflow.
Skip the comparison — just try ShrinkTo
Image compression + 27 PDF tools, browser-based privacy, no daily limit, no signup. Free forever.
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