Compress PDF — Reduce File Size to Any Target
Shrink your PDF to a specific size like 100KB or 1MB, or pick a quick preset. Pro Mode adds custom DPI/quality control, grayscale mode and batch compression for multiple files.
Processed entirely in your browser — never uploaded to any server
Enter any size — the tool will iteratively optimize toward it (best-effort).
How to Compress a PDF
From an oversized PDF to a target file size in a few clicks — no signup, nothing ever leaves your browser.
Everything above runs entirely in your browser — your PDF is never uploaded to a server, so your document stays completely private from start to finish.
Compress PDF Online — Reduce File Size to 100KB, 300KB or 1MB, Free
Compressing a PDF reduces its file size by lowering image resolution and quality, or by cleaning up its internal structure. This tool renders pages with pdf.js and rebuilds the file with pdf-lib, both running locally in your browser — pick a target size like 100KB, or a quick preset, and it optimizes toward it without ever uploading your file anywhere.
A scanned assignment, a lecture slide export, or a portfolio full of screenshots can easily balloon past what an email attachment limit or a university submission portal will accept. Desktop PDF software handles this, but it means installing something just for a task that takes thirty seconds. This tool does the same job — compress a PDF to a specific size — directly in a browser tab, on any operating system, with no installation and no account required.
1Two Compression Methods, and When to Use Each
| Method | How It Works | Typical Size Cut | Text Stays Selectable |
|---|---|---|---|
| Maximum Compression | Rasterizes each page into an optimized image | Largest — hits small KB targets | No |
| Keep Text Selectable | Structural cleanup only, text is untouched | 5–20% | Yes |
If the goal is hitting a specific number — under 100KB for a portal that rejects anything larger — Maximum Compression is the only method that gets there reliably, because it controls image resolution and JPEG quality directly. If the PDF needs to stay searchable, copyable or accessible to a screen reader, Keep Text Selectable is the right choice, with the trade-off that it won't shrink a file nearly as much.
2Simple vs Pro — Compression Control
| Feature | Simple Mode | Pro Mode (Free) |
|---|---|---|
| Light / Recommended / Strong presets | ✓ | ✓ |
| Target size: 100KB, 300KB, 500KB, 1MB | ✓ | ✓ |
| Keep Text Selectable mode | ✓ | ✓ |
| 2MB target & custom target size (any value) | — | ✓ |
| Manual DPI and JPEG quality sliders | — | ✓ |
| Grayscale conversion | — | ✓ |
| Before/After page preview | — | ✓ |
| Batch compress multiple PDFs + ZIP download | — | ✓ |
3Common Reasons to Compress a PDF
Scanned assignments and lecture slide exports are usually the biggest offenders — a 20-page scanned PDF at full resolution can easily exceed 30MB, well past most application-tracking system limits of 2–10MB. The Recommended preset typically brings that down by 70–90% while staying perfectly readable, and government forms or ID uploads that specifically ask for "under 100KB" are exactly what the 100KB target chip is built for. Cloud storage limits on a free account tier are another common trigger — compressing a folder of scanned receipts or old coursework before uploading can be the difference between fitting in the free tier and needing to pay for more space.
When a target like 100KB is selected, the tool doesn't guess once — it renders each page at a starting DPI and JPEG quality, checks the resulting size, and iteratively lowers those values until the output lands at or near the target, balancing size against remaining readability.
4Works the Same on Mac, Windows and Linux
Because this runs entirely as a web page rather than installed software, it behaves identically regardless of operating system — there's no separate download for Mac versus Windows, and no command-line setup required the way a tool like Ghostscript needs on Linux. Open the page in any modern browser, drag in a PDF, and the same pdf.js and pdf-lib libraries do the work locally, whether that's a MacBook, a Windows laptop, a Chromebook, or a Linux desktop. That also means there's nothing to keep updated and nothing that stops working after an OS update breaks a desktop plugin.
5Frequently Asked Questions
Built on real, open-source libraries — page rendering runs on pdf.js and the final file is assembled with pdf-lib, the same open-source tools used across the PDF Studio suite, following the ISO 32000 PDF specification rather than a proprietary format.
Related Tools
The rest of PDF Studio — other free PDF tools that pair well with compressing