Compress PNG Images Online
Free, private, no upload. Reduce PNG file size by up to 80% — right in your browser.
Compress PNG images online for free. 100% browser-based — files never uploaded. Reduce PNG file size by up to 80% without quality loss. Batch compression supported.
CompressFast is a pure browser-side image processing tool — no files are ever uploaded to any server during compression. Your files stay on your device, processing is fast, and privacy is absolute.
Detailed Usage Guide
PNG (Portable Network Graphics) is the go-to format when you need lossless quality — screenshots, logos, UI elements, and any image with text or sharp edges. But PNG files are notoriously large. A single screenshot can easily exceed 2-3MB, which slows down your website and eats storage.
CompressFast's PNG compressor tackles this with a two-pronged approach:
1. Lossless optimization via oxipng WASM — This is the star of the show. oxipng runs entirely in your browser as WebAssembly, trying multiple compression strategies (different zlib levels, Zopfli, PNG filter combinations) and automatically picking the smallest result. The output is pixel-perfect — every single pixel matches the original. Typical savings range from 20% to 60% for screenshots and UI images.
2. Lossy compression with color quantization — For cases where you're willing to trade a tiny bit of quality for dramatic size savings, we offer color bit-depth reduction (down to 2 bits per channel) and PNG quantization. A 24-bit PNG with millions of colors can become an 8-bit PNG with virtually no visible difference, slashing the file size by 50-80%.
When you combine these with our built-in resize tool, you can take a 1920×1080 screenshot at 2.5MB and turn it into a 1280×720 optimized PNG at 400KB — that's an 84% reduction, all without uploading a single byte to any server.
Privacy is baked in: every compression, every resize, every watermark runs inside a Web Worker in your browser. You can literally disconnect your internet after loading the page and everything still works. No server ever sees your files.
Why Choose CompressFast?
100% Private
Your PNG files never leave your device. All compression happens locally in your browser.
Lossless Compression
Powered by oxipng WASM — achieve up to 80% size reduction without any quality loss.
Batch 30 Images
Compress up to 30 PNG images at once. ZIP download all results in one click.
How to PNG Images Online
Drop or Select PNG Files
Drag PNG images into the upload area, click to browse, or paste from clipboard with Ctrl+V.
Choose Compression Settings
Select "Lossless" for maximum quality preservation, or adjust the quality slider for smaller files.
Download Compressed PNGs
Click download on each image, or use "Download All" to get a ZIP file of all compressed PNGs.
FAQ
Does PNG compression lose quality?
No — CompressFast offers lossless PNG compression powered by oxipng WASM. Your PNG images will be visually identical to the original while being up to 80% smaller.
Are my PNG files uploaded to a server?
Never. All compression happens locally in your browser using Web Workers. You can disconnect from the internet and it still works.
Can I compress multiple PNG files at once?
Yes — compress up to 30 PNGs at once for free (500 with Pro). All processed in parallel for maximum speed.
What is oxipng and how does it work?
oxipng is a lossless PNG optimizer that runs as WebAssembly (WASM) in your browser. It trial-runs multiple compression strategies — zlib, Zopfli, filter combinations — and picks the smallest result. Unlike lossy compression, oxipng guarantees pixel-perfect output every time.
Can I resize PNG images while compressing?
Yes. CompressFast includes a resize feature — set target width and height in pixels, or use one-click presets like 50%, 75%, 1080p, or 720p. The resize respects aspect ratio and never upscales small images, preserving quality.
What file size can I expect after PNG compression?
Results vary by content: screenshots and UI images typically compress 30-60%, while photographs as PNG may see 10-30% reduction. Images with large solid-color areas (logos, icons) can achieve up to 80% savings. The oxipng engine automatically finds the best strategy for each image.
Is there a file size limit for PNG compression?
Free users can compress PNG files up to 10MB each and 20 files per batch. Pro users get 50MB per file and 500 files per batch. There is also a monthly quota of 400 free compressions — reset at the start of each month.
Can I add watermarks to my PNG images?
Yes — CompressFast supports both text and image watermarks. Position them anywhere in a 9-grid layout, adjust opacity, rotation, and scale. All watermark rendering happens locally in your browser.