Why PNG Files Are So Large
PNG is a lossless format, which means it preserves every pixel of image data. This is excellent for quality but creates large files. Understanding why PNGs are large helps you choose the right compression strategy.
The Trade-Off: Quality Versus Size
PNG uses DEFLATE compression, the same algorithm used in ZIP files. While efficient for graphics with flat colors and sharp edges, it struggles with photographs and complex images. A PNG photo can be 5-10 times larger than the same image in JPG or WebP format.
Consider a typical scenario: a website hero image saved as a PNG might be 2 MB. The same image as a WebP could be 400 KB. That is an 80% reduction with no visible quality loss. For web performance, this difference is significant.
When PNG Makes Sense
PNG remains the right choice for logos, icons, screenshots, and any image requiring transparency. Its lossless nature ensures pixel-perfect quality. The challenge is balancing this quality with acceptable file sizes.
Common Causes of Large PNG Files
| Factor | Impact on File Size | Solution |
|---|---|---|
| High bit depth (32-bit) | Very High | Convert to 8-bit indexed PNG |
| Photographic content | Very High | Convert to JPG or WebP |
| Large dimensions | High | Resize to display dimensions |
| Unnecessary metadata | Low to Medium | Strip EXIF data |
| Wrong format choice | Very High | Convert to WebP or AVIF |
The most impactful way to compress a PNG image is often to convert it to a more efficient format. Modern formats like WebP and AVIF provide dramatically better compression while maintaining quality.
Convert PNG to WebP for Better Compression
WebP is the best alternative to PNG for most use cases. Developed by Google, it provides 25-35% better compression than PNG for lossless images and 25-35% better than JPG for lossy images. It also supports transparency, making it a true PNG replacement.
Why WebP Compresses Better Than PNG
WebP uses advanced compression algorithms that PNG cannot match. It employs predictive coding and entropy coding techniques that reduce file size without sacrificing quality. For web developers, this translates directly to faster page loads and better Core Web Vitals scores.
Browser support for WebP is now excellent. All modern browsers support it, including Chrome, Firefox, Safari, and Edge. This means you can safely use WebP as your primary image format with PNG as a fallback for older browsers.
Real-World Example
A company logo saved as a 90 KB PNG becomes a 25 KB WebP with identical visual quality. That is a 72% reduction in file size. For a website with 20 such images, the cumulative savings significantly improve page load time.
How to Convert PNG to WebP
Converting PNG to WebP is straightforward. You can use online tools, command-line utilities, or desktop software depending on your needs.
Steps to convert PNG to WebP online
- Navigate to the PNG to WebP converter
- Upload your PNG files (up to 50 at once)
- Select lossless or lossy compression (lossy provides smaller files)
- Click "Convert" and wait for processing
- Download your WebP files as a ZIP archive
For developers, command-line tools like cwebp offer precise control. You can integrate WebP conversion into build scripts for automated optimization:
cwebp -q 85 input.png -o output.webpThe -q 85 flag sets quality to 85%, which typically provides the best balance between file size and visual quality. You can learn more about WebP conversion in our WebP format guide.
When to Use AVIF Instead
AVIF is the next-generation image format that pushes compression even further. It can achieve 50% smaller file sizes than PNG while maintaining the same visual quality. For maximum compression, AVIF is the best choice.
AVIF vs WebP vs PNG Comparison
| Format | Compression vs PNG | Transparency | Browser Support |
|---|---|---|---|
| PNG | Baseline | Yes | Universal |
| WebP | 25-35% smaller | Yes | Excellent (96%+) |
| AVIF | 50% smaller | Yes | Good (91%+) |
AVIF uses the AV1 video codec for image compression, which is significantly more advanced than WebP. The trade-off is slightly lower browser support, though this improves continuously.
Converting PNG to AVIF
The workflow for converting PNG to AVIF is similar to WebP. Online converters handle the technical details automatically, making it accessible to anyone.
Steps to convert PNG to AVIF
- Go to the PNG to AVIF converter
- Upload your PNG files
- Choose your quality setting (75-85% recommended)
- Process and download your AVIF files
Progressive Enhancement Strategy
For production websites, consider using the <picture> element to serve AVIF to supporting browsers while falling back to WebP or PNG for others. This ensures maximum compression where possible without breaking compatibility.
AVIF is particularly effective for photographs and complex images. A PNG photo that is 2 MB might become a 400 KB AVIF. That level of compression directly impacts your website's performance metrics.
Converting PNG to JPG for Photos
While WebP and AVIF are excellent formats, JPG remains the most universally compatible option. If your PNG contains photographic content, converting to JPG often produces the smallest file size with acceptable quality trade-offs.
When JPG Beats PNG
JPG uses lossy compression, which permanently discards some image data. This sounds bad but is actually ideal for photographs. The human eye is less sensitive to the type of data JPG removes, so the quality loss is often imperceptible at appropriate settings.
- Use JPG for — Photographs, complex images with gradients, images without transparency
- Keep PNG for — Logos, icons, text, images with transparency, images requiring pixel-perfect accuracy
Quality Settings for PNG to JPG Conversion
When converting PNG to JPG, the quality setting is crucial. Higher quality means larger files. Finding the right balance depends on your use case.
| Quality Setting | File Size vs PNG | Best Use Case |
|---|---|---|
| 90-100 | Similar or larger | Archival, print |
| 75-85 | 60-80% smaller | Web images, email |
| 50-70 | 80-90% smaller | Thumbnails, previews |
A quality setting of 75-85 typically provides the best balance for web use. The file size reduction is substantial while visual quality remains high.
Transparency Loss
JPG does not support transparency. Any transparent areas in your PNG will be filled with a solid color (usually white) when converted to JPG. If you need transparency, use WebP or AVIF instead.
To convert PNG to JPG, use our PNG to JPG converter. Learn more about JPG format benefits and when to use it.
Batch Convert and Compress PNGs
Processing PNG files one by one is inefficient. For websites with many images or large projects, batch conversion is essential. Modern tools allow you to convert dozens or hundreds of PNGs simultaneously.
The Batch Conversion Workflow
A professional batch workflow involves uploading all your PNGs, selecting the output format and quality settings, and processing them as a group. The converted files are then packaged into a ZIP archive for easy download.
Steps for batch PNG conversion
- Gather all PNG files you need to convert
- Drag and drop the entire folder onto the converter
- Select your target format (WebP, AVIF, or JPG)
- Choose quality settings appropriate for your use case
- Process and download the ZIP archive with all converted files
Security and Privacy Considerations
When uploading multiple files, especially client work or sensitive images, security matters. Professional conversion tools should provide transparent privacy protections.
| Security Feature | Why It Matters |
|---|---|
| TLS 1.3 Encryption | Protects files during upload and download |
| EU Data Residency | Ensures GDPR compliance |
| Auto-Delete Policy | Files removed automatically after processing |
Convert.FAST processes files on encrypted EU servers and deletes them automatically after one hour. This approach protects your data while providing the convenience of online conversion.
Performance Metrics
Convert.FAST processes typical PNG conversions with a p50 (median) response time of 0.7 seconds and p95 of 2.9 seconds for 12 MB images. This performance makes batch processing practical even for large projects.
For users who need to keep files in PNG format but want smaller sizes, Compress.FAST offers specialized PNG compression. This is useful when you cannot change formats but still need to reduce file size.
Your PNG Compression Questions Answered
Here are direct answers to common questions about compressing PNG images.
Does compressing a PNG reduce quality?
It depends on the method. Lossless PNG compression reduces file size without changing any pixel data. The image remains identical to the original.
Converting PNG to a lossy format like JPG, WebP, or AVIF with quality settings below 100 will reduce quality slightly. However, at appropriate settings (75-85%), the difference is usually imperceptible while file size drops by 50-80%.
What is the best format to compress PNG images?
WebP is the best overall choice. It provides 25-35% better compression than PNG while supporting transparency. Browser support is excellent at over 96%.
AVIF offers the best compression (50% smaller than PNG) but has slightly lower browser support at 91%. Use it when maximum compression is priority.
JPG is best for photographs where you do not need transparency. It is universally supported and produces small file sizes.
Can I keep transparency when compressing a PNG?
Yes, but only if you convert to formats that support transparency. WebP and AVIF both support alpha channels (transparency), making them ideal PNG replacements.
JPG does not support transparency. Converting a transparent PNG to JPG will fill transparent areas with a solid color, typically white.
If you must keep the PNG format but want smaller files, use a specialized PNG compression tool that optimizes without converting formats.
How do I compress a PNG without converting formats?
If you must keep the PNG format, there are several techniques to reduce file size:
- Reduce bit depth — Convert 32-bit PNGs to 8-bit indexed PNGs. This reduces the color palette from millions to 256 colors, which is sufficient for most graphics.
- Remove metadata — Strip EXIF data, comments, and other metadata that adds size without affecting the image.
- Use PNG optimizers — Tools like OptiPNG or pngquant can reduce PNG file sizes by 20-40% through better compression algorithms.
For online PNG compression without format conversion, Compress.FAST provides specialized PNG optimization tools.
Convert.FAST handles PNG to WebP, AVIF, and JPG conversion on encrypted EU-based servers. Files are automatically deleted after one hour for privacy.
Stewart Celani
Founder
15+ years in enterprise infrastructure and web development. Stewart built Tools.FAST after repeatedly hitting the same problem at work: bulk file processing felt either slow, unreliable, or unsafe. Convert.FAST is the tool he wished existed—now available for anyone who needs to get through real workloads, quickly and safely.
Read more about Stewart