Compress PDF
Reduce PDF file size by re-encoding pages — with an honest report of the result.
Portals cap uploads at 2 MB and your scan is 11 MB. This re-renders each page at a lower resolution and re-encodes it, which is the compression approach that actually works in a browser — and it tells you honestly when a file will not get smaller.
Your file never leaves your device. It is read and processed by JavaScript running in this tab. Nothing is uploaded or stored.
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What the Compress PDF does
Compression works well on scanned documents, because the bulk is high-resolution page images that can be re-encoded smaller. It works badly on text PDFs, where the content is already compact vector instructions and there is nothing large to shrink — rasterising such a file can make it bigger.
The tool reports the actual before and after sizes rather than promising a percentage, and if the result is larger it says so and tells you to keep the original.
How to use this tool
- Check the current size first with the file size checker so you know your target.
- Select the PDF and choose a resolution. 120 DPI is a good starting point for documents that will be viewed on screen.
- Set the JPEG quality. 70% is a reasonable balance; below 50% text starts to look rough.
- Press Compress PDF and compare the before and after sizes.
- If the reduction is not enough, try a lower resolution rather than lower quality — resolution has a much larger effect.
How the size reduction works
Each page is rendered to a canvas at the chosen DPI,
encoded as JPEG at the chosen quality, and placed on a new
page of the original dimensions.
Pixels per page ∝ DPI²
Halving DPI cuts the pixel count to a quarter.
This is why resolution matters far more than quality.
Works well on: scanned documents, image-heavy PDFs
Works badly on: text-only PDFs, already-compressed files
The cost: every page becomes an image. Text is no longer
selectable or searchable.
Worked example
Example: a scanned 10-page document
| Original | 11.4 MB, scanned at 300 DPI |
| At 120 DPI, 70% quality | about 1.6 MB |
| Reduction | roughly 86% |
| Readability | fine on screen, slightly soft in print |
The same settings applied to a 300 KB text-only PDF would produce a larger file, because text costs almost nothing to store while page images cost a great deal.
What your result means
The reported reduction is the real one, measured on the file produced. No percentage is promised in advance because it depends entirely on what is inside your document.
"No reduction achieved" means your PDF is already efficient — almost always a text document. Keep the original; splitting or removing pages is the better route.
Text becomes unselectable. That is inherent to this method. If you need searchable text, do not compress this way.
Important considerations
- Resolution affects size far more than quality, because pixel count rises with the square of DPI. Try 96 DPI before dropping quality below 60%.
- Compressed pages cannot be searched or have text copied from them. Keep the original if that matters.
- For a text-heavy PDF, removing pages or splitting the document reduces size far more effectively than compression.
- Genuine text-PDF compression requires font subsetting and stream optimisation, which browsers cannot do. Desktop tools can.
- Some portals check the page count and dimensions as well as the size, both of which are preserved here.
- Compressing an already-compressed file again degrades quality without much further saving.
Limitations of this tool
- Password-protected PDFs cannot be opened without the password and will report an error rather than failing quietly.
- Everything runs in your device's memory, so very large documents can be slow or exhaust available memory.
- Damaged or partially downloaded files cannot be parsed.
- Every page becomes an image, so text is no longer selectable, searchable or accessible to screen readers.
- Text-only PDFs will not shrink and may grow. The tool detects this and tells you to keep the original.
- Font subsetting and content-stream optimisation, which desktop tools use, are not achievable in a browser.
Frequently asked questions
How much can a PDF be compressed?
It depends entirely on the content. Scanned documents commonly drop by 70–90%. Text-only PDFs barely shrink at all, and may grow. The tool reports the real figure rather than promising one.
Why did my PDF get bigger?
Because it was a text document. Text is stored as compact instructions; converting each page into an image replaces that with far more data. Keep the original — it is already efficient.
Will I still be able to search the text?
No. This method renders pages as images, so text is no longer selectable or searchable. That is the trade-off for a large size reduction.
What settings should I use for a 2 MB upload limit?
Start at 120 DPI and 70% quality, then check the result. If it is still too large, drop to 96 DPI — resolution reduces size much faster than quality does.
Is there a better way to reduce size without losing text?
In a browser, no. Removing pages or splitting the document works without rasterising. Desktop tools such as Acrobat can subset fonts and optimise streams, which browsers cannot.