HTTP compression, otherwise known as content encoding, is a publicly defined way to compress textual content transferred from web servers to browsers. HTTP compression uses public domain compression algorithms, like gzip and brotli, to compress HTML, JavaScript, CSS, and other text files at the server. This standards-based method of delivering compressed content is built into HTTP 1.1, and most modern browsers that support HTTP 1.1 support ZLIB inflation of deflated documents. In other words, they can decompress compressed files automatically, which saves time and bandwidth. https://developer.mozilla.org/en-US/docs/Web/HTTP/Compression​

In Iris you can enable the best offered compression with a single line of code:

app.Use(iris.Compression)

The first, iris.Compression is a middleware which enables writing compressed data to the client and allows server to read compressed data from the client.

To enable compression on all server's responses and requests:

func main() {
    app := iris.New()
    app.Use(iris.Compression)
​
    app.Post("/data", handler)
}
​
func handler(ctx iris.Context) {
    response := iris.Map{"name", "kataras"}
    ctx.JSON(response)
}

If you want to enable only writing and not reading compressed data, you can skip the iris.Compression and use the ctx.CompressWriter(true) alone, and visa-versa.

func handler(ctx iris.Context) {
    ctx.CompressWriter(true)
​
   // [...]
}

There is also the Context.ClientSupportsEncoding(s ...string) bool method which reports if the client does accept and support gzip encoding:

func handler(ctx iris.Context) {
    if ctx.ClientSupportsEncoding("gzip") {
        // client expects and supports gzip replies.
    } else {
        // client does not support gzip.
    }
}

That's all, your handlers will send and/or receive compressed data automatically, no further actions are required.

Q/A

How Iris selects the compression algorithm to use on write?

• Iris reads the request's Accept-Encoding header value, if it contains more than one compression algorithm then it negotiates best candidate and compress data using the selected algorithm. By-default browsers accept the gzip one.

How Iris selects the algorithm to decompress the request body?

• Based on the request's Content-Encoding header value.

What are the builtin compression algorithms?

• ​"gzip"​

• ​"deflate"​

• "br" brotli​

• ["snappy"](https://en.wikipedia.org/wiki/Snappy_(compression)) and

How can I see the selected algorithm used to write and read?

• You have to import "github.com/kataras/iris/v12/context" package to access the Iris writer and reader types.

func handler(ctx iris.Context) {
    if cw, ok := ctx.ResponseWriter().(*context.ResponseCompressWriter); ok {
        alg := cw.Encoding
        // [...]
    }
​
    if cr, ok := ctx.Request().Body.(*context.CompressReader); ok {
        alg := cr.Encoding
        // [...]
    }
}