How to Compress PDF Files in Python

What Is IronPDF and Why Use It for PDF Compression?

IronPDF is a Python PDF library that handles creation, reading, editing, and optimization of PDF documents. It works with files generated from scratch, converted from HTML, or loaded from disk. Its compression API targets images, which are the primary contributor to large PDF sizes.

The CompressImages method accepts a quality integer from 1 to 100 and an optional boolean that scales images down to their visible resolution. This dual-parameter design lets you tune compression precisely: a high-traffic reporting dashboard might use quality 70 to keep visuals sharp, while an internal archive system might use quality 40 to maximize storage savings. The library handles all encoding internally, so no additional dependencies are required.

IronPDF is part of the Iron Suite, which covers document creation, barcode processing, OCR, and ZIP archiving, all from a shared Python installation. For developers already using IronPDF to create PDFs from scratch, compression slots in as a natural follow-on step before saving or distributing files.

How Do You Install IronPDF in Python?

:path=/static-assets/ironpdf-python/content-code-examples/how-to/python-compress-pdf/install.sh
:ProductInstall

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:ProductInstall

After installation, configure your license key for production environments. IronPDF includes a free 30-day trial that covers all features, including compression, with no credit card required. The PyPI package page lists the latest release notes and dependency details.

How Do You Compress PDF Files Using IronPDF?

Pass a quality integer to CompressImages to reduce the size of embedded images across the entire document. Lower integers produce smaller files at the cost of image fidelity; higher integers preserve more detail. The example below shows both a standard compression call and an advanced call that also scales images down to their visible size.

:path=/static-assets/ironpdf-python/content-code-examples/how-to/python-compress-pdf/compress-basic.py
from ironpdf import PdfDocument

# Load the PDF document from a file
pdf = PdfDocument("Image based PDF.pdf")

# Compress images to quality 60 (lower numbers increase compression)
pdf.CompressImages(60)
pdf.SaveAs("document_compressed.pdf")

# Advanced: also scale images down to their visible size in the PDF
# Note: scaling can affect image clarity if pages are resized later
pdf.CompressImages(90, True)
pdf.SaveAs("Compressed.pdf")

// THIS CODE SNIPPET IS NOT AVAILABLE!
from ironpdf import PdfDocument

# Load the PDF document from a file
pdf = PdfDocument("Image based PDF.pdf")

# Compress images to quality 60 (lower numbers increase compression)
pdf.CompressImages(60)
pdf.SaveAs("document_compressed.pdf")

# Advanced: also scale images down to their visible size in the PDF
# Note: scaling can affect image clarity if pages are resized later
pdf.CompressImages(90, True)
pdf.SaveAs("Compressed.pdf")

How Do You Apply Batch Compression to Multiple PDF Files?

Processing a folder of PDF files follows the same API: iterate over each .pdf file, load it with PdfDocument, call CompressImages, and save the result. The function below wraps that pattern into a reusable utility.

:path=/static-assets/ironpdf-python/content-code-examples/how-to/python-compress-pdf/batch-compress.py
import os
from ironpdf import PdfDocument

def batch_compress_pdfs(input_folder, output_folder, quality=60):
    """
    Compress all PDF files in a folder.

    Args:
        input_folder: Path to folder containing source PDFs
        output_folder: Path where compressed PDFs will be saved
        quality: Compression quality (1–100); default is 60
    """
    # Create the output folder if it does not exist
    os.makedirs(output_folder, exist_ok=True)

    for filename in os.listdir(input_folder):
        if filename.endswith(".pdf"):
            input_path = os.path.join(input_folder, filename)
            output_path = os.path.join(output_folder, f"compressed_{filename}")

            try:
                pdf = PdfDocument(input_path)
                pdf.CompressImages(quality)
                pdf.SaveAs(output_path)
                print(f"Compressed: {filename}")
            except Exception as e:
                print(f"Error compressing {filename}: {e}")

// THIS CODE SNIPPET IS NOT AVAILABLE!
import os
from ironpdf import PdfDocument

def batch_compress_pdfs(input_folder, output_folder, quality=60):
    """
    Compress all PDF files in a folder.

    Args:
        input_folder: Path to folder containing source PDFs
        output_folder: Path where compressed PDFs will be saved
        quality: Compression quality (1–100); default is 60
    """
    # Create the output folder if it does not exist
    os.makedirs(output_folder, exist_ok=True)

    for filename in os.listdir(input_folder):
        if filename.endswith(".pdf"):
            input_path = os.path.join(input_folder, filename)
            output_path = os.path.join(output_folder, f"compressed_{filename}")

            try:
                pdf = PdfDocument(input_path)
                pdf.CompressImages(quality)
                pdf.SaveAs(output_path)
                print(f"Compressed: {filename}")
            except Exception as e:
                print(f"Error compressing {filename}: {e}")

The try/except block prevents a single corrupted or password-protected file from halting the entire batch. Logging the filename alongside the exception message makes it easier to identify which files need manual review. For higher-volume pipelines, consider splitting the folder into chunks and processing them in parallel threads.

What Quality Settings Should You Use for PDF Compression?

The right quality setting depends on how the PDF will be used after compression. Three ranges cover the most common scenarios.

High quality (70–90): Documents destined for printing or formal distribution benefit from staying in this range. Text stays sharp and diagrams remain legible at standard print resolutions. The file size reduction is modest, typically 10–25%, but the output is indistinguishable from the source for most readers.

Medium quality (50–70): This range suits web delivery and email attachments. Photographic content shows minor softening on close inspection, but the reduction in file size (often 25–50%) meaningfully improves load times and email deliverability. Most document management systems and portal uploads work well at quality 60.

Aggressive compression (30–50): Internal archives, long-term storage backups, and documents that will not be printed can use this range. At quality 40, images are noticeably softer, but text rendered by the PDF engine (rather than embedded as images) remains fully crisp. This approach is also appropriate for documents that will be converted to images and resized before display.

How Do You Verify Compression Results in Python?

Checking the output file size programmatically confirms that compression met your target before the file moves to the next step in a pipeline. Python's built-in os.path.getsize returns the byte count for any file path, so verification requires no additional libraries.

:path=/static-assets/ironpdf-python/content-code-examples/how-to/python-compress-pdf/verify-compression.py
import os
from ironpdf import PdfDocument

# Load and compress the document
pdf = PdfDocument("report.pdf")
original_size = os.path.getsize("report.pdf")

pdf.CompressImages(60)
pdf.SaveAs("report_compressed.pdf")

compressed_size = os.path.getsize("report_compressed.pdf")
reduction_pct = (1 - compressed_size / original_size) * 100

# Report results to confirm compression was effective
print(f"Original:   {original_size / 1024:.1f} KB")
print(f"Compressed: {compressed_size / 1024:.1f} KB")
print(f"Reduction:  {reduction_pct:.1f}%")

// THIS CODE SNIPPET IS NOT AVAILABLE!
import os
from ironpdf import PdfDocument

# Load and compress the document
pdf = PdfDocument("report.pdf")
original_size = os.path.getsize("report.pdf")

pdf.CompressImages(60)
pdf.SaveAs("report_compressed.pdf")

compressed_size = os.path.getsize("report_compressed.pdf")
reduction_pct = (1 - compressed_size / original_size) * 100

# Report results to confirm compression was effective
print(f"Original:   {original_size / 1024:.1f} KB")
print(f"Compressed: {compressed_size / 1024:.1f} KB")
print(f"Reduction:  {reduction_pct:.1f}%")

The output gives a clear reduction percentage that can be logged or checked against a threshold. If the reduction falls below expectations, the document may contain few or no embedded images. In that case, the file size will remain largely unchanged regardless of the quality setting, since CompressImages targets raster images only. Text and vector graphics are unaffected by this method.

What Are the Next Steps for PDF Compression in Python?

IronPDF's CompressImages method gives Python developers a single, well-scoped API for reducing PDF file sizes. Adjust the quality parameter to balance storage savings against visual fidelity, and add the resolution-scaling boolean for a second reduction pass when output dimensions are fixed. For a broader look at what IronPDF handles, see the Python PDF library overview page.

Start your free trial to test compression alongside IronPDF's full feature set, including HTML to PDF conversion, digital signatures, form handling, and document merging. When the trial period ends, view licensing options to find the plan that fits your deployment.

Ready to see what else IronPDF can do? Explore the full Python PDF tutorial for a walkthrough of IronPDF's core capabilities.