Does compressing a PDF reduce its quality?

It depends on the mode. Preserve mode re-compresses embedded images but keeps selectable text, links and bookmarks. It refuses PDFs with fillable form fields. Aggressive mode turns every page into a JPEG image, which removes selectable text and document structure. Visual quality depends on the preset you choose.

Can I still select and copy text after compressing?

In Preserve mode, yes — selectable text survives compression. In Aggressive mode, no. Aggressive flattens each page to a raster image, so text is no longer selectable, searchable, or copy-able. If you need to keep text accessible, use Preserve.

Why did Preserve mode barely reduce my file size?

Text and vector graphics use little space in many PDFs. Preserve mode only re-compresses embedded images, so it may have little to change. Aggressive turns every page into an image. It may reduce a scan, but it can make a compact text PDF larger. You also lose selectable text.

What happens to fillable form fields?

Preserve mode refuses to compress PDFs that contain fillable form fields (AcroForms) rather than risk corrupting them silently. You will see a message explaining the refusal. Aggressive mode will process these PDFs, but it flattens form fields to images — they will no longer be fillable. If you need to keep form fields functional, keep the original file.

Is there a file size limit?

On the free tier the limit is 100 MB per PDF and up to 10 PDFs per batch. A Day or Project Pass raises that to 500 MB per file and 50 files per batch. Because processing happens in your browser's memory, your device is still the hard limit: phones and tablets may struggle with very large files even within those numbers. See the pricing page for details.

Is my PDF uploaded to a server?

No. The PDF Compressor processes the file entirely in your browser. The file stays on your device, so there is no server queue and no question of how long a copy is kept.

How to Compress a PDF Free in Your Browser

Why compress a PDF

PDFs accumulate weight quickly. Scanned documents can get large quickly when each page is a high-resolution image. Reports exported from design tools embed full-resolution graphics. Slide decks converted to PDF carry every image at its original size.

Large PDFs cause friction: email attachment limits bounce them, cloud storage fills up faster, and page-load times slow down when the PDF is hosted on a website. Compression removes that friction by reducing the file size while keeping the document usable.

Two modes: Preserve and Aggressive

The PDF Compressor offers two distinct compression strategies. They are not just quality levels — they work differently under the hood, and the tradeoffs matter.

Preserve mode (default)

Preserve mode re-compresses raster images inside the PDF. It keeps selectable text, links, bookmarks and vector graphics. It refuses PDFs with fillable form fields. The document structure stays intact in accepted files.

This is the right choice for invoices, reports, contracts and e-books where you need to copy text or click links after compression.

The tradeoff: if your PDF is mostly text and vector art with few embedded images, Preserve mode may not reduce the file size meaningfully. The tool will tell you when this happens.

One important limitation: Preserve mode refuses to process PDFs with fillable form fields (AcroForms). Rather than risk silently corrupting interactive fields, the tool blocks the operation and explains why. If you need to compress a PDF with form fields, you can use Aggressive mode — but the fields will be flattened to images and will no longer be fillable.

Aggressive mode

Aggressive mode renders every page of the PDF to a JPEG image at a resolution and quality level you choose, then assembles those images into a new PDF. The output is a flat image-based document.

This mode can reduce scanned and photo-heavy PDFs. The result depends on the source file and quality preset. It can also make a compact text PDF larger. Check the output before you replace the original.

The tradeoff is real: Aggressive mode removes selectable text, links, bookmarks, and form fields. The output cannot be made searchable again without running OCR on it (which this tool does not do). Always keep your original if you may need the text later.

Aggressive mode offers three quality presets:

Smallest file — maximum compression, lower visual quality. Good for archival copies you rarely view at full zoom.
Balanced — a middle ground between size and clarity.
Best quality — lighter compression, sharper images. Good for documents you still need to read on screen.

Step-by-step: compress a PDF

1. Open the PDF Compressor.

2. Drop one or more PDF files onto the upload area, or click to browse. You can also paste a PDF from your clipboard.

3. Choose Preserve (the default) or Aggressive. If you pick Aggressive, an inline warning reminds you that selectable text will be removed.

4. If you chose Aggressive, pick a quality preset: Smallest file, Balanced, or Best quality.

5. Click Compress. The tool processes each file in your browser, so it stays on your device.

6. Review the results. Each file shows its original size, compressed size, and the percentage reduction.

7. Download individual files or, if you compressed multiple PDFs, download them all as a single ZIP.

What to expect from file sizes

Compression results vary widely depending on the content of the PDF:

Scanned documents (image-based PDFs): Both modes re-compress image data. Either mode can produce a smaller file, but the result depends on the source images and quality preset.
Text-heavy reports and contracts: Preserve mode may produce little change because the text is compact. Aggressive mode can make these files larger and removes selectable text.
Design-heavy PDFs (marketing collateral, slide exports): Preserve mode can reduce embedded image data. Results depend on how the PDF was originally exported.

If Preserve mode reports minimal savings on a text-heavy PDF and you need a smaller file, consider whether losing selectable text is acceptable before switching to Aggressive.

Browser limits

All processing happens in your browser using JavaScript. The PDF never leaves your device, which is the privacy advantage — but it also means the tool runs within your browser's memory constraints.

Available memory varies by browser and device. Large files or batches can fail even when they meet the site limits. If the tab stops responding, compress fewer files or use a device with more memory.

Free-tier users have batch and file-size limits. See the pricing page for current thresholds.

How browser-local compression works (and its limits)

Most online PDF compressors upload your file to a remote server, process it there and send it back. The PDF Compressor does the work inside your browser instead:

1. You select or drop a PDF. The browser reads it into memory.

2. The tool parses the PDF structure: pages, fonts, images, form fields and metadata, using pdf-lib and the browser's built-in canvas APIs.

3. Depending on the mode, it re-encodes embedded images at a lower quality (Preserve) or renders each page to a compressed image (Aggressive).

4. The result is assembled into a new PDF and offered as a download.

5. When you close the tab, the browser discards the working memory.

No network request carries the file content. The page can request site assets and optional analytics after you accept. Analytics never receives your PDF or its contents.

That design has genuine limits, and it is better to know them up front:

No OCR. If the input is a scan with no text layer, the tool cannot make it searchable, and Aggressive output is never searchable.
No font subsetting. Unused font glyphs are not removed, so a PDF that embeds full font files keeps that weight.
No linearisation. The output is not optimised for fast page-by-page web viewing, a server-side feature some hosted tools offer.
Memory-bound. Very large PDFs (hundreds of high-resolution pages) can slow the tab or crash it. That is why the free tier caps files at 100 MB. A Day or Project Pass raises the cap, but your device's memory is still the hard limit.

If you need OCR, font optimisation or server-scale batches, a hosted or desktop tool is the better fit. For everyday invoices, scans, contracts and reports, browser-local means your file stays on your device, with no queue and no account.

Compress a PDF to under 1 MB (or for email)

Many email services and upload forms reject large attachments, and online forms often ask for a file under 1 MB or 2 MB. The tool does not let you type a target size, so work towards it in steps:

1. Run Preserve first. Check the result size shown for each file.

2. If it is still too large and the PDF is a scan or photo-heavy, switch to Aggressive and try Balanced, then Smallest file.

3. If it is still over the limit, split the PDF into parts, or extract only the pages you need, and compress those.

4. If the document started life as phone photos, rebuild it at a smaller size: resize the images first, then turn them into a PDF.

Keep the original. Aggressive mode removes selectable text, links and form fields, so only send the Aggressive version when a flat copy is acceptable.

When to use each mode

Scenario	Recommended mode
Emailing an invoice or contract	Preserve
Shrinking a scan for archival	Aggressive (Balanced or Smallest)
Reducing a slide deck export	Preserve first; Aggressive if savings are insufficient
Compressing a photo album PDF	Aggressive (Best quality)
PDF with fillable form fields	Keep original — Preserve refuses, Aggressive flattens fields

Related guides

How to Extract Pages from a PDF — pull specific pages into a new file.
How to Remove Pages from a PDF — delete unwanted pages and keep the rest.