The param_block setting "allows to specify URL param which will not be checked by redirector." This feature proves useful when URL signed protection is disabled, enabling you to restrict modifications to download settings configured at the account or domain level.

Suppose your account's default download speed is configured as 120% of video bitrate.

A standard link appears as:

Without URL signed protection enabled, users could manually adjust speed parameters:

However, if you add 'speed' to the param_block setting, such speed modifications become ineffective, preserving your configured download settings.