The proxy is highly effective against legacy URL filters and SNI-based blockers but fails against modern CSP or outbound traffic analysis.
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Here is a breakdown of how these work, the terminology used, and the technical landscape surrounding them. The proxy is highly effective against legacy URL
These sites provide lists of "mirrors"—external links that are not yet flagged by school filters. the terminology used
This is the most common use of Google Sites for unblocking. Because Google Sites is a legitimate productivity tool, most school and work firewalls (like GoGuardian or Lightspeed) whitelist the domain sites.google.com .