Reduce file size while optimizing for maximum PDF quality.
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Click the red Select PDF File button or drag and drop your PDF directly onto the page. No account or sign-up required. Your file is read instantly inside your browser — it never leaves your device.
Pick from three levels. Light makes a modest size reduction with no visible quality change — ideal for text-heavy documents. Medium is the best balance for most files. Strong achieves the smallest possible size — best when file size matters more than pixel-perfect image quality.
Click Compress PDF and your optimised file downloads directly to your device in seconds. The result shows you the original size, the new size, and how much was saved — so you can see exactly what was achieved.
Most email providers cap attachments at 10–25MB. A single PDF with scanned pages or high-resolution images can easily exceed this. Compressing the file before sending means it goes through first time, without needing to use a file-sharing link.
Job applications, tender submissions, visa applications and university portals often enforce strict file size limits — commonly 2MB, 5MB or 10MB. Compressing your PDF lets you stay within those limits without splitting or removing content.
A folder full of uncompressed PDFs can consume significant space on your phone, laptop or cloud storage. Compressing them regularly keeps your storage tidy and ensures you have room for new documents.
If you publish PDFs on a website — reports, brochures, price lists — file size directly affects how fast they load for visitors. A smaller PDF loads faster, reduces bounce rate and improves the experience for users on mobile connections.
WhatsApp, Telegram and similar apps have file size caps on documents. A PDF that is too large to send can be compressed to fit within those limits without any quality loss that is noticeable on a phone screen.
If you are building a digital archive of invoices, contracts or records, compressing each PDF as you save it keeps the archive manageable. Years of documents at a smaller size means lower storage costs and faster backups.
Light compression removes redundant internal data and optimises the file structure without touching images or fonts. The size reduction is modest — typically 5–15% — but quality is indistinguishable from the original. Best for documents where appearance is critical, such as contracts, presentations or portfolios.
Medium compression resamples images to a lower resolution that still looks sharp on screen and when printed at standard sizes. Size reductions of 20–50% are typical. This is the right choice for the vast majority of everyday PDFs — reports, invoices, forms and letters.
Strong compression applies aggressive image downsampling to achieve the maximum reduction in file size. Reductions of 50–80% are possible on image-heavy PDFs. The trade-off is that images may appear slightly soft when zoomed in or printed at large sizes. Ideal for scanned documents where readability matters more than sharp images.
It depends on the level you choose. Light compression has virtually no visible effect on quality — it only removes redundant internal data. Medium compression is barely noticeable for most documents. Strong compression reduces image resolution more aggressively, which can make images appear slightly soft when zoomed in. Text and vector graphics are never affected by compression at any level.
Results vary significantly based on the content of the PDF. Text-only documents typically compress 10–25%. PDFs containing scanned pages or high-resolution photographs can compress 40–80% on Strong level. The result screen shows you the exact before and after sizes so you always know what was achieved.
No. SlashPDF compresses your PDF entirely inside your browser using JavaScript. Your file is never transmitted to any server at any point. This also means compression is fast — there is no upload or download wait time, just local processing on your own device.
No. SlashPDF reads your file in memory and produces a new compressed output file. The original PDF stored on your device is never touched, modified or deleted. Both files exist independently after compression.
This can happen with PDFs that are already heavily optimised, or PDFs that contain mostly vector graphics and text with no images. In these cases there is little redundant data to remove and the file may not shrink meaningfully. If the compressed version is larger than the original, simply keep the original.
Yes. Scanned PDFs — which are essentially images embedded in a PDF container — often achieve the highest compression ratios because the images are large. Strong compression works particularly well on scanned documents where the goal is readability rather than perfect image sharpness.
PDFs with edit or print restrictions can usually still be compressed. Fully encrypted PDFs that require a password to open cannot be processed until the password protection is removed, as SlashPDF cannot access the content without it.
Yes. SlashPDF is fully responsive and works on iPhone, iPad, Android phones and tablets in any modern browser. Open slashpdf.com/compress-pdf/, select your file from your device, choose a compression level and download the result — no app installation needed.