[2] It achieves higher compression ratios than mainstream Deflate and zlib implementations at the cost of being slower.

[5] Zopfli can either generate a raw Deflate data stream or encapsulate it into gzip or zlib formats.

Under default settings, the output of Zopfli is typically 3–8% smaller than zlib's maximum compression, but takes around 80 times longer.

[12] The reference implementation is a software library under the terms of Apache License 2.0, written in C.[2] Since then, the open-source community made attempts to modify Zopfli for optimizing Portable Network Graphics (PNG) files because PNG uses a Deflate compression layer.

[13] The Zopfli algorithm has also been integrated into other PNG compression optimization tools like advpng (from the AdvanceCOMP utility suite)[14] and OxiPNG.