Compress PDF

What this PDF compressor actually does

PDF compression is not one single operation. A PDF may contain selectable text, embedded fonts, photographs, scanned pages, drawings, and internal objects that are larger than necessary. This tool examines the file in your browser and creates a separate optimized PDF. It can reorganize PDF objects, compress streams, remove unnecessary overhead, and—depending on the level you select—reduce the resolution and JPEG quality of embedded images.

The right result depends on what is inside your PDF. A text-heavy report may already be compact, while a scanned document or a PDF containing full-resolution photographs may become much smaller. The tool shows the original size, page count, compressed size, and calculated reduction after the operation so you can judge the result instead of relying on a promise that every file will shrink by the same percentage.

Upload by clicking or dragging a PDF

Start by clicking the upload area and selecting a PDF from your device, or drag a PDF onto the drop zone. The page accepts PDF files only. If a different file type is selected or dropped, the tool stops before processing and displays an invalid-file message. This prevents an image, document, or unrelated file from being sent to the PDF engine by mistake.

After you choose a file, the page reads it locally and briefly shows an analysis progress bar. It uses PDF.js to open the document and count its pages. If the file is damaged, unsupported, or encrypted in a way that needs a password, the tool explains that it could not read the PDF and resets the screen so you can try another file.

Review the file before compression

Once the PDF has been read successfully, the upload area changes into a file information panel. You can confirm the original file name, original size, and number of pages before pressing the compression button. This is useful when several files have similar names or when you want to make sure you selected the correct version of a document.

The panel also reserves space for the compressed size and reduction percentage. Those two values are filled in only after compression finishes. The reduction is calculated from the original byte size and the downloaded result, so it reflects the actual output for your document rather than a fixed marketing estimate.

Safe mode: preserve quality and optimize structure

Safe is the default choice and is designed for PDFs where preserving the existing appearance matters most. In this mode, the page sends the PDF to a QPDF WebAssembly worker for lossless-style structural optimization. It compresses streams, generates efficient object streams, recompresses Flate data, and improves the internal organization of the PDF without applying the image downsampling used by the stronger modes.

Choose Safe for contracts, text reports, forms, invoices, study notes, or any PDF where you do not want photographs and scanned pages re-encoded. It may produce a moderate reduction, especially when the original file already uses efficient compression. Because it prioritizes the existing quality, it is not always the smallest option.

Balanced mode: a practical size-quality compromise

Balanced is intended for everyday sharing. It uses a Ghostscript WebAssembly worker to rewrite the PDF and downsample embedded images to a moderate resolution. Color and grayscale images are handled at a lower resolution than Safe mode, monochrome content receives its own setting, and JPEG quality is reduced enough to save space while keeping normal documents comfortable to read.

After Ghostscript produces its result, the tool runs a second QPDF optimization pass. The extra result is used only when it is non-empty and no larger than the first result. If that optional pass fails, the tool keeps the valid Ghostscript output instead of discarding a usable compressed file. Balanced is a good starting point for mixed PDFs containing text, screenshots, diagrams, and ordinary photographs.

Maximum mode: prioritize the smallest practical file

Maximum applies stronger image reduction than Balanced. It uses lower target resolutions and a lower JPEG quality setting, then attempts the same aggressive QPDF optimization pass. This can make a noticeable difference for scanned pages, camera photographs, and image-heavy PDFs, especially when the file is being uploaded to a portal with a size limit.

Maximum is not the best choice for every document. Small text inside a scan, fine lines, screenshots, or detailed photographs can lose visual sharpness when their resolution and JPEG quality are reduced. If the PDF will be printed, archived, submitted as evidence, or inspected at high zoom, compare it with Safe or Balanced before choosing the final copy.

Understand the three compression choices

The percentages shown beside the choices are practical estimates, not guarantees. The final reduction depends on the original PDF, how its images were encoded, the number of pages, and whether it contains mostly text or scanned artwork. Use the presets as a decision guide:

• Safe: choose it when visual fidelity and selectable document content are the priority.
• Balanced: choose it when you need a meaningful reduction without making normal images look unnecessarily soft.
• Maximum: choose it when upload or storage size matters more than fine image detail.

If the first result is not suitable, you can select another radio option and compress the original file again. Each click starts from the original file held by the page, not from a previously compressed result, so repeated testing does not compound quality loss.

Compression runs in Web Workers

The heavy PDF engines run in separate browser workers. Ghostscript and QPDF are loaded as WebAssembly modules, which lets the page run the compression code on your device without a conversion request to our server. Moving the work off the main browser thread also helps the interface remain usable while a larger PDF is being processed.

The first compression can take longer because the browser may need to download and initialize the WebAssembly engine. The page warms up both workers after it becomes idle, so the engines can be ready before you click Compress PDF. Processing time still depends on the PDF size, page content, available memory, processor speed, and whether you are using a phone or computer.

Follow the progress and compare the result

When compression starts, the button is disabled temporarily and a progress message appears. The status may identify whether the file is being optimized losslessly or compressed for a smaller size. When the output is ready, the file information panel displays the compressed size and the percentage reduction calculated from the two files.

A smaller number is not the only measure of success. Open the downloaded PDF and check the pages you care about: small text, charts, signatures, photographs, and scanned pages. If the output is larger than expected or image quality is not right, try a different level and compare the actual files.

Your PDF stays in the browser

This compressor reads the selected file with the browser File API and passes its bytes to local Web Workers. The code does not submit the PDF to a MyPDF Guru conversion endpoint. The result is created as a browser Blob and downloaded directly to your device. The PDF engines may use temporary in-memory virtual files while they work; those are part of the browser process and are not a server-side file archive.

For sensitive documents, remember that browser extensions, device security, downloaded files, and any external resources in your browsing session are separate from this tool. Keep your browser updated, use a trusted device, and delete temporary copies when you no longer need them.

Use it on desktop, tablet, or phone

The compressor uses the same upload, quality, and download flow on desktop and mobile browsers. Drag and drop is convenient on a computer; on a phone, tap the upload area and choose the PDF from your files app. A phone may take longer with a large scanned document because compression needs memory and processor time, so keeping other demanding apps closed can help.

Download a separate compressed copy

When processing completes, the browser creates a new PDF and starts the download automatically. The name is based on the original file, followed by _compressed.pdf; for example, report.pdf becomes report_compressed.pdf. Your original file remains unchanged on your device.

Use the Clear file button when you want to remove the current selection from the page and start again. The tool asks for confirmation, clears the displayed size and page information, and returns the upload area to its initial state.

When should you compress a PDF?

Compressing is useful before attaching a report to email, uploading an assignment, submitting an application, sending invoices to a client, sharing scanned identity or travel documents through an approved portal, or keeping a large archive manageable. For a text-only PDF, start with Safe. For a mixed office document, Balanced is usually the practical first test. For a scan or photo-heavy file with a strict upload limit, test Maximum and inspect the result carefully.

Need another PDF task first?

A password-protected PDF may need to be opened with the correct password before PDF.js can analyze it. If you own the document and know its password, use the PDF Password Remover first, then return here to compress the unlocked copy. If you need to remove blank or unwanted pages before compression, use Remove PDF Pages first so you do not spend time optimizing pages you will later delete.