Page-aware image resampling
The engine measures each page and only scales down images that have more pixels than your chosen resolution can show. Multi-step filtering keeps edges smooth.
PDF tools · Free
Compress PDF: Free Online PDF Compressor That Keeps Quality
Make PDFs smaller for email, uploads and storage without blurring the text. The engine resamples only the images that are bigger than they need to be, keeps fonts and vector graphics untouched, and rebuilds the file leaner. Everything happens in your browser, so your documents stay on your device.
- 100% free, no limits
- Files never leave your device
- No sign up or watermark
- Works on phone, tablet and desktop
By Entertainment Couch · Updated
PDF compressorRuns in your browser · files are never uploaded · batch and ZIP supported
On-device · PrivateDrop PDFs here
Or choose them from your device. Add as many as you like; each one is compressed in turn.
- Text stays sharp
- Never larger than your original
Compression level
Fine-tune settings
Higher keeps more photo detail. Graphics and screenshots always stay lossless.
Images with more pixels than this, measured against the page size, are resampled down.
Your files
No files yet. Add a PDF above and it will appear here.
Compare quality
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Drag across the page to compare the original and compressed versions.
What is the Compress PDF tool?
Compress PDF is a free online tool from Entertainment Couch that reduces PDF file size in your web browser. It resamples oversized images to the resolution your pages need, keeps text and vector graphics untouched, and rebuilds the file more efficiently. Files are processed on your own device and are never uploaded, and you never get a file larger than the one you started with.
Compress PDF at a glance
| Price | Free. No limits on files, no watermark and no premium version. |
|---|---|
| Account | None. No sign-up, email or download. |
| Privacy | Files are processed in your browser and never uploaded to a server. |
| Devices | Any modern browser on phone, tablet, laptop or desktop. |
| Levels | 4: Lossless, Balanced, Strong and Smallest, plus fine-tune settings. |
| Typical reduction | 40% to 90% for scanned and photo-heavy PDFs. Text-only PDFs shrink less. |
| Keeps | Text, fonts, vector graphics, links, bookmarks and form fields (unless you flatten). |
| Batch | Compress many PDFs at once and save them as one ZIP file. |
| Quality check | Side-by-side before-and-after slider with zoom, page by page. |
| Made by | Entertainment Couch. Last updated 21 October 2026. |
How do you compress a PDF?
Add your PDF to the tool, pick a compression level and wait a few seconds. Check the result with Compare, then press Save PDF. No account, upload or software is needed.
- 1
Add your PDF
Drop one or more PDFs onto the tool or press Choose PDFs. Nothing is uploaded.
- 2
Pick a level
Balanced suits most files. Choose Strong for email and Smallest for strict upload limits.
- 3
Let the engine work
Each file is analysed, its images are optimized and the file is rebuilt in seconds.
- 4
Check and save
Use Compare to inspect quality, then press Save PDF, or Save all as ZIP for several files.
Which compression level should you choose?
Choose Balanced for most PDFs, Strong for email attachments and websites, and Smallest when an upload portal has a strict size limit. Choose Lossless when the document must stay visually identical, such as contracts or archived records.
| Level | Photo quality | Resolution limit | Flattening | Best for |
|---|---|---|---|---|
| Lossless | Unchanged | Unchanged | No | Contracts, archives, files that must stay identical |
| Balanced | 80 | 200 DPI | No | Everyday use and sharp home printing |
| Strong | 66 | 150 DPI | No | Email attachments, websites and on-screen reading |
| Smallest | 50 | 110 DPI | When 15% smaller | Upload portals with strict size limits |
Every level keeps text and vector graphics untouched. You can adjust image quality, resolution, grayscale, metadata removal and flattening yourself under Fine-tune settings.
How does it reduce PDF size without losing quality?
Most of a large PDF’s size comes from images stored at far higher resolution than the page needs. The tool scales those images down to your chosen DPI, re-encodes photos efficiently, leaves text and vector graphics alone, and removes data the file doesn’t use.
Content-aware encoding
Every image is sampled for colour variety. Photos and scans get tuned JPEG encoding, while charts, logos and screenshots stay lossless so they don’t pick up blurry artefacts.
Text and vectors untouched
Fonts, text and vector drawings are left exactly as they are, so text stays crisp at any zoom and remains selectable and searchable.
Structure cleanup
Unused objects are removed, uncompressed data is deflated at maximum level, and objects are packed into object streams for a leaner file.
Never-larger guarantee
A recompressed image is only kept if it is at least 3% smaller. If the whole file can’t be reduced, you get your original back unchanged.
Optional flattening
For scans and image-only files, pages can be rendered as images. This is only used when it saves at least 15% more, and the tool tells you when it happens.
How much can a PDF be compressed?
Scanned and photo-heavy PDFs typically shrink by 40% to 90% at the Balanced or Strong level. Text-only PDFs usually shrink by less than 30%, because text is already compact. Results depend on how the original file was made.
| Type of PDF | Typical reduction | Why |
|---|---|---|
| Scanned documents | 50% to 90% | High-resolution page images are resampled and re-encoded. |
| Photo-heavy brochures and reports | 40% to 80% | Large photos are scaled to page size and recompressed. |
| Slides exported to PDF | 20% to 70% | Screenshots stay lossless; oversized photos shrink. |
| Text-only documents | 0% to 30% | Mostly structure savings, because text is already compact. |
| PDFs already optimized | Often 0% | Your original is returned unchanged. |
Figures are typical ranges, not guarantees. The tool never returns a file larger than your original.
How can you get the smallest PDF with good quality?
Start with Balanced, lower the resolution limit only as far as your use needs, try grayscale for black-and-white paperwork, and flatten only image-only scans. Always check the result with Compare before sending it.
- Start with Balanced. It usually removes most of the excess size with no visible change. Step up to Strong only if the file is still too big.
- Match resolution to use. 150 DPI is plenty for screens and email, 200 DPI for sharp home printing and 300 DPI for professional print.
- Try grayscale for paperwork. Black-and-white scans of forms, receipts and letters shrink further with grayscale turned on.
- Flatten scans, not text documents. Flattening helps image-only scans but makes text unselectable, so leave it off for documents you need to search or copy from.
- Always compare before you send. Open Compare, zoom in on small print and photos, and check a few pages.
Is it safe to compress PDFs online?
With this tool, yes. Your PDF is compressed entirely inside your web browser and is never uploaded, stored or seen by anyone else. That makes it safe for contracts, bank statements, medical records and other private documents.
Many online PDF compressors send your file to a server, process it there and ask you to download the result. This tool works differently: the compression engine is loaded into the page, and your file is read, rebuilt and saved locally. Once the page has loaded you can even disconnect from the internet and keep working.
Removing metadata also strips hidden details such as the app that created the file and page thumbnails, which can be useful before sharing a document publicly.
Key terms in PDF compression
Short definitions of the ideas behind the tool and its settings.
- DPI (dots per inch)
- How many image pixels fit into one inch of the printed page. 150 DPI looks sharp on screens; 300 DPI is print quality.
- Lossy compression
- Compression that throws away detail the eye is unlikely to notice, such as JPEG. It gives the biggest savings for photos.
- Lossless compression
- Compression that keeps every pixel and character exactly, such as Deflate. Used for text, graphics and the Lossless level.
- JPEG
- The standard lossy format for photographs. Inside a PDF it appears as DCTDecode image data.
- Deflate
- The lossless algorithm behind PDF’s FlateDecode filter and ZIP files.
- Object stream
- A PDF feature that packs many small objects into one compressed block, cutting file overhead.
- Flattening (rasterizing)
- Turning a page into a single image. It can shrink scans a lot but removes selectable text, links and form fields.
- Metadata
- Hidden information stored in a file, such as the creating app, XMP data and page thumbnails.
About the Compress PDF tool
Who makes the tool, exactly what it changes in your file, its limits, and the standards it follows.
Who made it
Compress PDF is designed and maintained by Entertainment Couch, which also publishes a collection of free online tools and free browser games. It was last updated on .
What the engine changes
- Images are resampled only when they have more pixels than the page can show at your resolution limit, measured against the largest page in the document.
- Images with many colours, such as photos and scans, are re-encoded as JPEG at your quality setting. Images with few colours, such as charts and screenshots, are kept lossless with Deflate.
- Uncompressed and weakly compressed data streams are recompressed with Deflate at maximum level [3], and objects are packed into object streams as defined in the PDF standard [1].
- Objects that nothing in the document refers to are removed. With Remove metadata on, XMP metadata, thumbnails and editor leftovers are removed too.
- A change is kept only if it makes the data at least 3% smaller, and the finished file is only used if it is smaller than the original.
Known limits
- CMYK, JPEG 2000 and JBIG2 images are left unchanged to avoid colour shifts.
- Embedded fonts are kept in full, so text-heavy files shrink less than image-heavy ones.
- Password-protected PDFs can be compressed only with flattening on, and only if they open without a password.
- The maximum file size depends on your device’s memory.
Sources
- ISO 32000-2:2020. Document management: Portable document format, Part 2: PDF 2.0. International Organization for Standardization. www.iso.org/standard/75839.html
- ITU-T Recommendation T.81 (1992). Digital compression and coding of continuous-tone still images (JPEG). www.w3.org/Graphics/JPEG/itu-t81.pdf
- P. Deutsch (1996). RFC 1951: DEFLATE Compressed Data Format Specification version 1.3. IETF. www.rfc-editor.org/rfc/rfc1951
- Mozilla. PDF.js, the open-source PDF renderer used for previews and flattening. mozilla.github.io/pdf.js
- pdf-lib, the open-source JavaScript library used to read and rebuild PDF structure. pdf-lib.js.org
More free tools on Entertainment Couch
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Frequently asked questions
Search, or pick a topic. Using the tool, quality, privacy, file limits and more.
General
What is the Compress PDF tool?
Compress PDF is a free online tool from Entertainment Couch that makes PDF files smaller in your web browser. It resamples oversized images, keeps text and vector graphics untouched, and rebuilds the file structure more efficiently. Files are processed on your device and never uploaded.
Is Compress PDF really free?
Yes. Every level and feature is free, with no limit on the number of files, no watermark and no premium version.
Do I need to sign up or install anything?
No. There is no account, email or download. Open the page, add a PDF and compress it.
Can I compress a PDF online without uploading it?
Yes. This tool compresses PDFs entirely inside your browser. Your file is read and rebuilt on your own device and is never sent to a server, which makes it suitable for private and confidential documents.
How do I reduce the size of a PDF for email?
Add the PDF, choose the Strong level and save the result. Strong resamples images to 150 DPI, which looks sharp on screen and usually brings large files under the 20 to 25 MB attachment limit that many email services use.
How do I compress a PDF on iPhone or Android?
Open this page in Safari or Chrome, tap Choose PDFs and pick a file from Files, Drive or Downloads. When it finishes, tap Save PDF to keep the smaller copy on your phone.
Can I compress several PDFs at once?
Yes. Add as many PDFs as you like. They are compressed one after another, and when two or more are done you can save them together with Save all as ZIP.
Using the tool
How do I compress a PDF?
Drop your PDF onto the tool or press Choose PDFs, pick a compression level, wait a few seconds while the engine works, then press Save PDF. Use Compare first if you want to check quality.
Which compression level should I choose?
Balanced is best for most files and keeps images at up to 200 DPI. Strong (150 DPI) suits email and web. Smallest (110 DPI, with flattening allowed) is for strict upload limits. Lossless changes no images and only optimizes the file structure.
What do the fine-tune settings do?
They let you set image quality from 30 to 95, choose a resolution limit from 96 to 300 DPI or no limit, convert images to grayscale, remove metadata, and allow flattening. Changing a setting after compressing shows a Recompress with new settings button.
What does “No reduction” mean?
It means the file was already well optimized and no setting could make it smaller, so your original is kept unchanged. Try a stronger level or a lower resolution limit for more reduction.
How can I check the quality before saving?
Press Compare on a finished file. Drag the slider across the page to see the original on the left and the compressed version on the right, zoom up to 4×, and step through every page.
How long does compression take?
Most files take a few seconds. Large scans with hundreds of high-resolution pages can take a minute or more, depending on your device.
Quality & levels
Will compressing a PDF reduce its quality?
The Lossless level changes no images at all. The other levels only change images that are larger or heavier than needed, and photos are re-encoded at the quality you choose. Text, fonts and vector graphics are never altered unless you flatten pages.
Does compression affect the text in my PDF?
No. Text and fonts are kept exactly as they are, so they stay sharp, selectable and searchable. Only the optional flattening setting turns pages into images.
What DPI should I use?
Use 150 DPI for screens, email and casual printing, 200 DPI for sharp home or office printing, and 300 DPI for professional print. Lower values make smaller files.
What is flattening and when should I use it?
Flattening renders each page as a single image. It can greatly shrink scanned documents, but text is no longer selectable and links and form fields are removed. The tool only uses it when it is turned on and saves at least 15% more than normal compression.
Will links, bookmarks and form fields still work?
Yes, with normal compression. The document structure, including links, bookmarks, annotations and form fields, is kept. Flattened files keep only the page images.
Why were some images not compressed?
Images are skipped when changing them could alter colours or appearance, such as CMYK print images, JPEG 2000 and JBIG2 images, masks and very small images. Images that would not get at least 3% smaller are also kept.
Can compression make my PDF bigger?
No. Each image is only replaced if the new version is smaller, and if the finished file is not smaller than the original, the tool gives you the original back.
Privacy & security
Are my files uploaded to a server?
No. The compression engine runs in your browser using JavaScript. Your PDF is read, processed and saved on your own device and is never transmitted anywhere.
Is it safe to compress confidential documents?
Yes. Because files never leave your device, contracts, medical records, bank statements and other private documents stay private. You can even disconnect from the internet after the page has loaded.
Does the tool work offline?
Yes. Once the page has fully loaded, you can go offline and keep compressing files.
What does Remove metadata delete?
It removes the XMP metadata stream, page thumbnails, editor-specific leftovers and the Producer, Creator and Keywords fields. The document title and author are kept.
Files & limits
Is there a maximum file size?
There is no fixed limit. Because everything runs on your device, the practical limit depends on its memory. Computers usually handle files of several hundred megabytes; on phones, files under about 100 MB work best.
Can I compress a password-protected PDF?
Yes, if you turn on flattening and the PDF opens without a password. If it asks for a password to open, remove the protection in your PDF reader first.
Does it work on scanned PDFs?
Yes, and scans usually shrink the most, often by 50% to 90%, because they consist of large page images. Turning on grayscale helps further for black-and-white paperwork.
Why did my text-only PDF barely shrink?
Text is already very compact, so there is little to remove. Most of the size in text documents comes from embedded fonts, which are kept to make sure the document looks right.
Will my PDF stay PDF/A compliant?
Not necessarily. Rebuilding the file and removing metadata can break PDF/A conformance. If archive compliance matters, use the Lossless level with Remove metadata turned off and validate the result.
Technical help
Which browsers are supported?
Any up-to-date version of Chrome, Edge, Firefox, Safari, Samsung Internet or Opera on Windows, macOS, Linux, Android, iPhone and iPad. JavaScript must be enabled.
The tool is slow or stopped responding. What can I do?
Very large files use a lot of memory. Close other heavy tabs, compress one large file at a time, and on phones try a lower resolution limit.
Is the tool accessible?
Yes. Every control works with a keyboard, buttons have text labels, and animations are reduced automatically when your device has the reduced-motion setting turned on.
How do I report a problem?
Use the contact options on Entertainment Couch and tell us what happened, which device and browser you used, and roughly how large the file was. Please don’t send the file itself if it is private.