Estimate data saved with compression.
Compression only helps on traffic that is not already compressed. Text, JSON, HTML, logs and uncompressed databases shrink well, often 3:1 or better; video, images, audio and encrypted payloads are already dense and gain almost nothing. Applying the ratio only to the compressible share, and leaving the rest untouched, gives a realistic overall reduction instead of the headline ratio — which is why a 2.5:1 engine yields well under 60 percent in practice.
Blended compression saving
Compressible GB = total x share; compressed total = compressible / ratio + incompressible; saved = total - compressed total
On a typical mixed connection, 40-60 percent. Web APIs, text and code compress well, while video streaming and image-heavy browsing — often the bulk of the bytes — do not, because they are already encoded.
Not at the application layer. Gzip and Brotli operate inside the TLS session and are used by nearly all modern web servers. It does prevent transparent compression by an intermediate proxy, which is why network-level compression appliances have become far less effective.
On text, gzip typically reaches 3-4:1 and Brotli 4-5:1. Log files and database dumps can exceed 10:1. Already-compressed formats such as JPEG, MP4 and ZIP gain 1-2 percent at best.