Response compression

Easel CDN compresses eligible responses at the edge based on the client Accept-Encoding header. Compression reduces transfer size for HTML, CSS, JavaScript, JSON, and other text-like content.

Preferred algorithms

When the client advertises support, Easel prefers:

1. Brotli (br)
2. gzip

If the client does not send Accept-Encoding, or only requests encodings Easel does not apply, the response is sent uncompressed.

When compression applies

Easel compresses a response when all of the following are true:

• The client accepts br or gzip.
• The response is not already encoded (Content-Encoding is empty).
• The response is not a partial range response.
• The body is large enough to benefit (at least 256 bytes for complete-body responses).
• The Content-Type is on the compression allowlist.
• The compressed body is smaller than the original.

When Easel applies compression, it sets Content-Encoding and merges Vary: Accept-Encoding so caches distinguish encodings correctly.

Allowlisted content types

Easel compresses common text and structured formats, including:

• Application: JSON and related (json, ld+json, manifest+json, …), JavaScript, XML feeds, WASM, and similar
• Text: HTML, CSS, JavaScript, plain text, markdown, CSV, and similar
• Images: SVG, BMP, and ICO (not JPEG, PNG, WebP, or video)
• Fonts: OpenType (otf) and TrueType (ttf)

Already-compressed formats such as JPEG, PNG, WebP, MP4, and WOFF2 are not re-compressed. Compressing them again usually wastes CPU and can increase size.

Checking compression

Inspect the response in your browser or with curl:

curl -sI -H "Accept-Encoding: br, gzip" https://www.example.com/

Look for Content-Encoding: br or Content-Encoding: gzip.