The output generated by Zopfli is typically 3–8% smaller compared to zlib at maximum compression, and we believe that Zopfli represents the state of the art in Deflate-compatible compression. Zopfli is written in C for portability. It is a compression-only library; existing software can decompress the data. Zopfli is bit-stream compatible with compression used in gzip, Zip, PNG, HTTP requests, and others.

Due to the amount of CPU time required, 2–3 orders of magnitude more than zlib at maximum quality, Zopfli is best suited for applications where data is compressed once and sent over a network many times — for example, static content for the web.