Definition of the maximum size (content-length)

i3, our image management solution, allows you to dynamically and transparently restrict the maximum size (Content-Length) of your images by applying a progressive degradation in their quality.

To achieve this, we use our TCDN-i3-transform header, specifying the desired operation type, which in this case is max_length. Unlike other operations, such as conversion to WebP format, this operation requires a mandatory parameter: the maximum size that the resulting image will have. This parameter has the format <size>[<unit>], where if no unit is specified, it is implicitly assumed to be in bytes. The accepted values for <unit> are b (bytes), k (kilobytes), and m (megabytes). For example, a valid value could be 640k.

The exact syntax for this operation is as follows: max_length:<size>[<unit>].

Unlike the quality operation, this operation is not restricted to a specific image format.

For instance, if you wanted all the images in your domain under the URL /estaticos/imagenes to be served with a maximum size of 1 MiB, you would simply deploy a VCL configuration similar to the following from the dashboard:

# i3 - max_length
sub vcl_recv {
    if ( == "") {
        if (req.url ~ "^/estaticos/imagenes/") {
            set req.http.TCDN-i3-transform = "max_length:1m";

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