How this works in your browser
The two modes work in genuinely different ways. Standard mode keeps the PDF structure intact and targets the embedded images: each is decoded, re-encoded at a lower quality and written back, while text remains as vector glyph instructions so it stays sharp at any zoom and fully selectable. Strong mode takes a heavier approach, rendering each page to a bitmap through PDF.js and rebuilding the document from those images. That discards the text layer entirely, which is exactly why it compresses so much further and why the output is no longer searchable. Both run through pdf-lib in your browser with no upload.
Compress PDF vs. traditional online converters
| Feature | Compress PDF (in-browser) | Traditional online converters |
|---|---|---|
| File upload required | No - never leaves your device | Yes - file is sent to a server |
| Processing queue | None - starts instantly | Often, especially at peak times |
| Watermark on output | Never | Common on free plans |
| Usage limits | None - free, unlimited use | Often capped per day or file size |
| Works offline once loaded | Yes, for most tools | No - requires a live connection |
| Account required | No | Often, for anything beyond a trial |
How to use Compress PDF
- 1
Open the Compress PDF tool
Go to tools.slaytic.com and open the Compress PDF tool. No sign-up or account required.
- 2
Drop your PDF and pick a mode
Drop the file in and choose Standard to keep text selectable, or Strong to rasterise pages for maximum size reduction.
- 3
Download the smaller file
The compressed document is written in your browser and offered for download, typically 20-70% smaller depending on content.
Common ways to use Compress PDF
Getting under an email attachment limit
Bring a report or portfolio under the typical 10-25MB cap most mail servers enforce, without splitting it up.
Uploading to a portal with a size cap
Meet the file size limits imposed by job applications, tender submissions and government forms.
Shrinking scanned documents
Scans are the best case for compression, since every page is an image and often scanned at far higher resolution than reading requires.
Frequently asked questions
How much smaller will my file be?
Typically 20–70% smaller. Image-heavy PDFs compress the most. Text-only PDFs with no embedded images may see only modest reduction.
What is the difference between Standard and Strong modes?
Standard reduces image quality while keeping text as vector (sharp at any zoom). Strong converts every page to a rasterised image for maximum size reduction but may slightly soften very small text.
Will compression affect text selection or search?
Standard mode preserves selectable text. Strong mode converts pages to images, so text is no longer selectable in the output - run OCR afterwards if searchability is needed.
Why did my PDF barely shrink?
Almost certainly because it is text and vector graphics rather than photos. Compression works by reducing embedded image data, so a document with no images has very little to remove. Scanned documents, which are really pages of images, compress the most.
Can I compress the same PDF twice?
You can, but the second pass gives you very little and costs real quality, because it re-compresses images that were already degraded. If Standard was not enough, switch to Strong on the original rather than stacking passes.
Which mode should I choose?
Start with Standard: it keeps text sharp and selectable, which is what you want for anything someone will read or search. Only reach for Strong when hitting a hard size limit matters more than text staying selectable.