Compress PDF Online
Reduce your PDF file size quickly and easily. Compression runs entirely in your browser — your document is never uploaded to a server.
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Tap to choose a PDF file
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Your files stay on your device
Compression uses the same in-browser processing as our merge and split tools. Your PDF is read from your device, processed locally and never uploaded to a server.
About this compress PDF tool
This tool tries to make a PDF smaller in two different ways and keeps whichever result is genuinely lighter. First it rewrites the document's internal structure to strip redundant data. Then, depending on the level you choose, it re-renders the pages and stores them as compressed images at a lower resolution.
The saving you see reported is measured, not estimated: the original size and the new size are compared, and if neither approach produces a smaller file the tool tells you so instead of handing back a fake result.
Understanding size versus quality
Where the megabytes actually are
In most heavy PDFs, almost all the weight comes from images: scanned pages, phone photos and screenshots stored at far higher resolution than any screen or printer needs. Text and vector graphics contribute very little.
Two different kinds of saving
Rewriting the file's structure removes duplicated and unused data without touching a single pixel — that saving is free. Re-rendering pages as images trades visible detail for size, which is why it is offered as a choice rather than applied silently.
How much is enough
Compress to meet a specific limit, not as far as possible. A 4 MB file that must fit a 5 MB inbox needs the gentlest setting; pushing to Maximum only makes the pages harder to read for no benefit.
When a page must stay searchable
If the recipient will copy text out of the document or search it, stop at the level that preserves the text layer. Once pages are rasterised, the words are a picture of words.
How to reduce PDF file size
- 1
Choose your PDF
Select a file or drag it in. Documents made from scans and photos usually shrink the most, because images are what makes a PDF heavy.
- 2
Pick a compression level
Recommended keeps pages sharp for everyday sharing. Strong pushes further for email attachments. Maximum produces the smallest file and is best for drafts or receipts.
- 3
Check the saving and download
The result shows the original size, the new size and the percentage saved. Download the compressed PDF, or run it again at a different level if you need more.
When shrinking a PDF helps
Get past upload limits
Application portals, tax sites and contact forms often cap attachments at a few megabytes. Compression is usually the fastest way under the line.
Email attachments that send
Mail providers reject oversized messages. A smaller PDF sends first time instead of bouncing back.
Tame heavy scans
Phone-scanned pages are stored at very high resolution. Re-rendering them at a sensible resolution can cut the size dramatically.
Honest results only
If the file is already efficient, the tool keeps the original rather than producing a larger or degraded copy.
Common use cases
Fit an application portal's limit
Reduce a scan or application packet when the upload field accepts a smaller maximum than the original file.
Send a document by email
Bring a photo-heavy attachment below the mail provider's message limit while keeping it readable.
Make phone scans easier to handle
Downsample pages captured at unnecessarily high camera resolution for faster opening and sharing.
Store routine records efficiently
Shrink receipt, invoice and archive copies when perfect print detail is less important than convenient storage.
Practical examples
A scan rejected by an upload form
Six pages scanned at high resolution come to 18 MB against a 5 MB limit. Scanned pages are images, so this is exactly the case compression handles well — the text stays legible on screen while the file drops far below the cap.
A merged application packet for email
The combined file is a few megabytes over a mailbox limit. A light pass is usually enough, and it is worth stopping there: the less the pages are redrawn, the sharper small print stays.
A text-only document that barely shrinks
A contract exported from Word is already compact, because text costs very little space. If the saving is only a few percent, the file was not the problem — check whether the limit applies to the whole message, attachments included.
A file that must stay searchable
If the recipient will search or copy the text, avoid the strongest setting, which redraws each page as a picture. That produces the smallest file but leaves nothing selectable behind. Removing unneeded pages first is the safer route.
Compression happens in your browser
Your PDF is read, analysed, re-rendered and rebuilt on your own device using the same local processing as the merge and split tools. It is never uploaded to a server, queued for processing or stored anywhere.
That means salary documents, invoices and identity scans can be compressed without ever being transmitted over the internet.
What the tool does with your document
Before compressing
The file is read locally and its size recorded, so the before-and-after figures shown to you are real measurements of your own file rather than a generic promise.
During compressing
Both approaches run on your device and the outputs are compared. Whichever is smallest while still being a valid PDF is the one offered; if neither beats the original, the original is kept.
After compressing
The compressed copy exists only as a download. Your original file is untouched on disk, so you can always go back to the full-quality version if a reviewer asks for it.
Performance on different devices
Compression is the heaviest of these tools because pages may be re-rendered one by one. A laptop will finish a long scanned document noticeably faster than a phone, though both produce the same file.
Files up to 100 MB are accepted and the first 60 pages are processed, which keeps memory use within what mobile browsers allow. Keep the tab in the foreground on a phone — background tabs are throttled and the job will crawl.
It runs in current versions of Chrome, Edge, Firefox and Safari on desktop and mobile. No plug-in, extension or desktop application is involved at any stage.
Tips for best results
Check the target limit first
If a portal accepts 10 MB and your PDF is 11 MB, Recommended is a better first choice than Maximum.
Keep a full-quality original
Compression creates a new file. Retain the source in case small print or photographs need closer inspection later.
Inspect text after strong compression
Open the result and zoom into signatures, figures and fine print before submitting it.
Remove pages before lowering quality
Splitting out unneeded appendices can save more space than compression and keeps the remaining pages untouched.
Compress PDF questions
How much smaller will my PDF get?
- It depends entirely on the file. Image-heavy scans often drop by 80% or more, while a short text-only document may barely change because there is little redundant data to remove.
Will the text still be selectable?
- When the structural optimisation wins, yes. When pages are re-rendered as images to reach a much smaller size, the text becomes part of the picture and can no longer be selected or searched.
Which level should I choose?
- Start with Recommended and download it. Only move to Strong or Maximum if the file still exceeds the limit you are trying to meet.
Why did nothing shrink?
- Some PDFs are already well optimised. In that case the tool reports no reduction and gives you back the original file untouched.
Is there a file size limit?
- Files up to 100 MB are accepted, and the first 60 pages are processed. Very large documents depend on the memory your device has available.
Is PDF compression free?
- Yes. All three levels and the resulting download are available without payment.
Do I need an account?
- No. There is no registration, sign-in or email request.
Is the file uploaded for compression?
- No. Analysis, page rendering and PDF creation take place locally inside your browser.
Does compression work on mobile?
- Yes, although long scanned files finish faster on a computer with more memory. Keep the tab open and in the foreground.
Which format can I upload?
- This tool accepts PDF files and produces a PDF. For photos, convert them with JPG to PDF first.
Is a watermark added?
- No. The result has no PDF Toolkit branding or added footer.
What happens to the file when the tab closes?
- The browser releases the selected file and temporary compressed copy from memory; nothing remains on the website.