Tool facts
- Input and output
- image/png → image/png
- Files per operation
- 1
- Total input limit
- 100 MiB
- Processing
- In your browser; no file upload
- Account
- Not required
- Price
- Free
Scope of these facts
- Selected file contents stay in the browser for processing. Loading the website and its separate usage analytics can still use the network.
- Verification covers the declared checks for supported files, not independent certification or acceptance by another portal. A format-signature check is not digital-signature validation.
- JavaScript, the required browser APIs and sufficient device memory are needed. Limits are admission ceilings, not a guarantee for every file, browser or iPhone.
- Lossless applies to decoded pixels and transparency for accepted PNG variants. Supported non-image chunks are preserved; this is not a metadata-removal tool.
How it works
- Select one PNG image.
- Choose Compress PNG to optimize its lossless data packing locally.
- Download only if the new PNG is smaller and passes pixel-data, transparency and decoding checks.
Lossless optimization, not JPEG conversion
PNG stores image data without JPEG-style quality loss. This tool repacks the compressed image data and compares the complete decompressed scanlines afterwards. It does not resize, quantize colors or convert your PNG to another format.
Transparency stays intact
The image header, alpha data and supported transparency chunks stay unchanged. Accepted color and metadata chunks are retained byte for byte. This tool is not a metadata removal service.
Why a PNG may not get smaller
A well-optimized PNG already packs its pixels efficiently. Repacking cannot guarantee further savings. This tool offers a download only when the output is genuinely smaller; otherwise your original remains the best available result within this strategy.
Supported PNGs and privacy
This initial version accepts non-interlaced 8-bit grayscale, RGB, grayscale-alpha and RGBA images. Palette images, 16-bit PNGs, animation, compressed metadata such as ICC profiles and unknown chunks are declined. The current file-size, pixel-count, dimension, chunk and Worker limits are shown in the technical facts above. Processing stays on your device with no file upload.
Frequently asked questions
Is this PNG compression lossy?
No. The filtered image data and supported non-image chunks must match exactly after recompression. No colors or transparency values are intentionally removed.
Will a transparent background turn white?
No. Alpha and transparency are preserved. This tool never silently converts to JPEG.
Why are some valid PNGs rejected?
The first version supports a bounded subset that can be verified safely. Interlaced, palette, 16-bit, animated and compressed-metadata variants need additional support before they can be processed here.
Does PNG compression work on mobile?
Yes, in browsers supporting native compression streams and image decoding. Large images can exceed a phone’s available memory and will fail without a download.