Compress PDF: Shrink Files in Your Browser, Without Uploading
A free PDF compressor that runs entirely in your browser. Three presets (Light, Recommended, Strong) cover most workflows, and a Custom mode unlocks DPI and JPEG quality sliders for fine control. Smallpdf gates Strong compression behind a $9/month Pro plan; we ship every quality level free. Sejda caps free use at 50 MB and 3 tasks per hour; we do not. Most importantly, the file never leaves your device, which makes this the safe option for tax records, contracts, medical files, and anything else you would not entrust to a third-party server.
Drop your PDF here, or click to choose
Compression runs in your browser. Nothing is uploaded.
🔒 The PDF is compressed in your browser. Confirm zero uploads in Developer Tools → Network.
Six reasons people choose Gizmoop's PDF compressor
The differences that matter when you are shrinking files you would not upload to a stranger's server.
Three presets plus full custom
Light (150 DPI, 90% JPEG), Recommended (110 DPI, 75% JPEG), Strong (90 DPI, 60% JPEG), or set your own DPI and JPEG quality. Smallpdf only offers two and gates Strong behind Pro.
100% browser-based
Compression uses pdfjs-dist + pdf-lib in your browser. Confidential documents (tax PDFs, contracts, medical reports) stay on your device. Confirm via Developer Tools → Network.
No upload, signup, or daily limit
Smallpdf caps free use at 2 tasks per day. Sejda caps at 50 MB and 3 tasks per hour. Gizmoop has no caps because the file never leaves your browser.
Grayscale option
Convert to grayscale for an extra 30-50% reduction on color documents. Useful for B&W printing, archive copies, and internal review where color is not needed.
Honest reduction stats
After compression, see the original size, compressed size, and exact percentage reduction. No fake "up to 99%" marketing; real numbers per file.
Privacy for sensitive PDFs
Tax records, signed contracts, medical scans, and HR documents all benefit from compression for sharing. Doing it locally means the file never reaches a third-party server.
When you need to compress a PDF
Real workflows where the file size limit is blocking the next step.
Getting a PDF under 10 MB or 25 MB for email
Gmail caps attachments at 25 MB. Most corporate mail at 10 MB. The Strong preset typically gets a 50 MB scanned PDF under 10 MB without quality issues for most readers.
Compressing scanned documents
Scans from office MFPs default to high DPI and produce huge PDFs. Compressing to 100 DPI keeps print-quality but cuts size 70-90%.
Web upload size limits
Forms that accept PDF uploads often cap at 5 MB or 10 MB (tax filings, school applications, job applications). Compress to fit the limit.
Archiving long-term
Storing decades of records on local drives or cloud storage adds up. Compressing once cuts storage 30-70% without losing legibility.
Mobile bandwidth
Sharing PDFs over cellular data is slow and costly with large files. Compress before sharing to make mobile viewing fast.
Printer queue limits
Office print servers sometimes reject documents over 50 MB. Compressing first sidesteps the issue while keeping print quality.
About compressing PDFs
What makes PDFs big, how compression actually works, and what Gizmoop does differently.
What actually makes a PDF big?
Three things contribute to PDF file size, in roughly decreasing order. First, embedded images: scanned documents and photo-heavy reports often dedicate 80-95% of their bytes to image data. Second, embedded fonts: corporate-style documents with non-standard fonts carry the font files inside the PDF, which can add 200 KB to a few MB. Third, metadata and structural overhead: title, author, keywords, thumbnails, JavaScript, form definitions, and embedded files. For most documents, images dominate. That is why every effective PDF compressor focuses primarily on images.
If your PDF is small (under 1 MB) and made of text, there is not much to compress; the text encoding is already efficient. If your PDF is large (10+ MB) and image-heavy or scanned, compression can typically cut 50-90% of the size without obvious visible loss at typical reading distances.
How this compressor works
Our tool uses a render-then-re-embed approach. For each page in your PDF, pdfjs-dist renders the page to a canvas at your chosen DPI (resolution). The canvas is then encoded as a JPEG at your chosen quality level. The JPEG is embedded as a single image filling the page in a fresh PDF document built with pdf-lib. The result is a PDF that visually looks like the original at the selected resolution but is encoded as a sequence of JPEG images rather than mixed text and image content.
This approach has one trade-off worth knowing about: text in the output is no longer selectable. The text is now part of the page image, not stored separately. For documents where text searchability matters (legal exhibits, technical manuals, archival records), this trade-off may not be acceptable; keep the original PDF for that purpose and use a compressed copy only for sharing. For documents where the visual content is the deliverable (scanned forms, image-heavy reports, sharing-only copies), the trade-off is well worth the size savings.
Three presets, explained
Light (150 DPI, 90% JPEG) aims for near-original quality with modest savings (20-40% reduction on typical documents). Text in the rendered image remains crisp at normal viewing distance and prints cleanly on a standard office printer. Use for documents where appearance matters more than size.
Recommended (110 DPI, 75% JPEG) is the balanced default (40-70% reduction). Text remains readable on screen and acceptable on print. Most users will find this preset matches their needs. iLovePDF's "Recommended" tier targets a similar quality level.
Strong (90 DPI, 60% JPEG) maximises size reduction (60-90% on image-heavy PDFs). Text is still readable on screen but visibly softer; printed output is acceptable for internal use, not for client-facing print. Use when you absolutely need the smallest file (email attachments, web upload caps).
Custom exposes both knobs (DPI 60-200, JPEG quality 40-95%) for fine control. Useful when none of the presets quite fit your file, or for experimenting with the trade-off.
Why Smallpdf gates Strong behind Pro and we do not
Smallpdf monetizes by limiting free users to "Basic" compression. To get aggressive compression (their "Strong" tier), users must upgrade to Pro at $9/month or $108/year. This works as a business model because compression is one of the most-needed PDF operations and Smallpdf has high traffic on the free tier.
Gizmoop's business model is different: we display ads on the surrounding pages and the tools themselves are free, including aggressive compression. There is no Pro tier and no upsell. Compress as many PDFs as you want, at any quality level. This is sustainable because we do not have server costs to amortise; the compression runs on your CPU, not ours.
Grayscale option
If your document does not need color in the output, converting to grayscale before JPEG compression cuts another 30-50% off the file size. Color JPEGs encode three channels (red, green, blue); grayscale encodes one. The reduction is largest on documents that already have predominantly grayscale content (text, line drawings, monochrome scans) because the color channels in those documents add bytes without contributing visible information.
Common uses: producing a B&W print-ready copy of a color report, archiving documents where future viewing is for content not appearance, internal review copies sent to many people. Keep grayscale off if your document has meaningful color content (photos, charts where color encodes data, branded material).
Email size limits and the practical playbook
Mail provider attachment limits are the single most common reason people compress PDFs. Gmail: 25 MB. Outlook personal: 20 MB. Outlook 365 default: 35 MB. Yahoo: 25 MB. Enterprise mail systems often impose 10 MB or lower. Practical playbook: try Recommended first; if still too large, try Strong; if still too large, enable grayscale. If your source PDF is huge (200+ MB scanned book), also consider splitting into separate files (our Split PDF tool can split a large PDF into chunks each under a size limit).
Working with very large PDFs
Because compression runs in your browser, the practical limit is your device's available memory and patience. Desktops with 8+ GB RAM handle 200-500 MB source PDFs comfortably. Mobile devices and lower-RAM machines may struggle past 100 MB. The progress bar shows per-page progress so you always know how far through the document the tool is. If your browser tab hangs on an enormous PDF, retry on a desktop or try splitting the file first.
Will Acrobat, Preview, Chrome, and Edge open the result?
Yes. The output is a standards-compliant PDF (PDF 1.7) with embedded JPEG content. Every modern PDF reader opens it without issue. Print quality matches what the chosen DPI would deliver in any other JPEG-based output. The file is also portable across operating systems and devices.
What does not survive this compression
Selectable text becomes part of the page image (not selectable, not searchable in PDF readers). Form fields are rasterised into the page image (no longer fillable). Annotations and comments are baked into the image (no longer editable). Digital signatures invalidate because the file content changed. Hyperlinks are lost (the URL text is still visible but no longer clickable in the output). For workflows where any of those properties matter, do not compress with this tool; the trade-off is too steep. Use this tool when the visual content is the deliverable.
How we differ from PDF24, iLovePDF, Sejda, and Smallpdf
PDF24 has the most granular server-side controls (DPI slider, JPEG quality, grayscale, font subsetting, metadata strip, stream dedup) but still uploads your file. iLovePDF has three quality tiers and 100 MB free upload cap. Sejda has multiple PPI presets and grayscale, but caps free use at 50 MB and 3 tasks per hour. Smallpdf has two tiers with Strong gated behind Pro. Gizmoop matches the preset feature set (3 quality tiers plus custom plus grayscale), removes every cap, and runs entirely in your browser, which makes it the only fully local option in this comparison.
Why "up to 99% reduction" claims are misleading
Most server compressors advertise dramatic reduction figures ("up to 99%") because the headline catches attention. In practice the actual reduction depends on the input. Already-efficient text-only PDFs may shrink 5-15%. Heavily image-laden PDFs may shrink 90%+. The honest framing is: most users will see 50-80% reduction on Recommended preset, with bigger savings on Strong, and the result table after compression shows the exact number for your specific file.
Chaining with other tools
Common compression workflows include other steps. To compress a password-protected PDF, unlock it first with our Unlock PDF tool (you must know the password). To send a compressed PDF privately, run our Protect PDF tool afterward to re-encrypt with a new password. To clean up a document before compressing, use Delete PDF Pages to drop unneeded pages, or Rotate PDF to fix sideways scans. Every step runs in your browser, so a confidential document can pass through the full chain without ever leaving your device.
Frequently asked questions
If you don't find your question here, ask us directly.
Drop your PDF, pick a preset (Light, Recommended, or Strong), optionally toggle grayscale, and click Compress PDF. The tool re-renders each page at a lower resolution and re-encodes it as a JPEG inside a fresh PDF. Everything runs in your browser; nothing is uploaded.
It depends on the input. Image-heavy or scanned PDFs typically shrink 60-90% on Strong, 40-70% on Recommended, 20-40% on Light. Already-compressed PDFs or text-only PDFs may shrink less. The result table after compression shows the exact reduction.
This compressor rasterises each page, so text in the output is no longer selectable. The visual appearance of text depends on DPI: 90 DPI (Strong) is fine for screen reading but slightly soft; 150 DPI (Light) prints cleanly. For documents that must stay text-searchable, use a different workflow (e.g. keep the original; share only with people who need a smaller version).
Smallpdf gates Strong compression behind a Pro subscription ($9/month). Gizmoop offers Strong, Recommended, Light, and full custom mode (DPI + JPEG quality sliders), all free, all in-browser. No daily quota like Smallpdf, no 50 MB cap like Sejda.
No. Compression uses pdfjs-dist and pdf-lib running in your browser. Open Developer Tools → Network during compression to confirm zero outbound transfers. Sensitive documents (financial statements, tax records, medical reports) stay on your device.
Converts every page to grayscale before JPEG compression. Color images have three channels (R, G, B); grayscale has one. The data reduction is roughly 30-50% on top of whatever the DPI/quality preset already saves. Useful when color is not needed in the output (text-only documents, B&W scans, internal review copies).
Start with Recommended. If the result is still too large, try Strong. If still too large, enable grayscale. For very large source PDFs, also consider splitting first (our Split PDF tool has a "Under X MB" mode that produces smaller files without compression at all).
No hard limit. Desktops handle 200 MB to 1 GB+ PDFs because processing is local. Mobile is more constrained at around 100 MB. Sejda blocks files over 50 MB on free; iLovePDF blocks over 100 MB. We do not.
Yes. The output is a standards-compliant PDF (PDF 1.7) with embedded JPEG content. Every modern reader opens it without issue. Print quality matches what you would expect for the chosen DPI.
Diminishing returns. A PDF that was already compressed once may shrink another 10-30% on Strong, but each pass loses more quality. Repeated heavy compression is visible. Run compression once at the right level rather than compounding passes.
No. Because the compressor rasterises pages, form fields, annotations, comments, and digital signatures are converted into the page image and become non-interactive. For documents where interactivity matters, do not use this compressor. For documents where the visual content is what matters, this is the trade-off for the size savings.
A few specific cases produce slightly larger output: very low-resolution source PDFs already encoded as JPEG, or PDFs at the smallest DPI presets when the source was already small. The tool shows the actual result honestly; if you see a positive percentage, try a lower DPI or higher compression preset, or accept that the source is already efficient.
All four upload your file to their servers. Smallpdf gates Strong behind Pro. iLovePDF offers three tiers, all server-side. PDF24 has the most granular controls (DPI, JPEG, grayscale, font subsetting, metadata stripping) but still uploads. Sejda caps free at 50 MB and 3 tasks per hour. Gizmoop has no caps, no upload, no signup, and a custom mode with full slider control.
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