Articles & Guides
Useful resources for web developers and system administrators
DNS
AdGuard DNS Addresses: 94.140.14.14 Setup and What It Blocks
AdGuard DNS: 94.140.14.14 and 94.140.15.15 block ads and trackers, 94.140.14.15 is the family filter, 94.140.14.140 is unfiltered. DoH, DoT, DoQ.
DNS
Quad9 DNS 9.9.9.9: Addresses, Setup and Malware Blocking
Quad9 DNS: 9.9.9.9 and 149.112.112.112 block malicious domains, 9.9.9.10 is unfiltered, 9.9.9.11 adds ECS. IPv6, DoH and DoT setup, vs 1.1.1.1.
Performance
Forced Reflow: When Reading the DOM Costs You a Frame
Browsers batch layout work until something reads a geometry value. Do that inside a loop that writes, and one recalculation becomes one per iteration.
DNS
Ghost Domain: Why a Removed Delegation Still Resolves
A resolver learns your nameservers from two places, and the second one can refresh itself forever. That is why a nameserver migration can outlive its own TTL.
Performance
content-visibility: Skipping Work the User Cannot See
Browsers lay out and paint pages nobody has scrolled to. One property skips that work — and without its companion, it trades rendering time for a jumping page.
Performance
Speculation Rules: Prerendering Pages Before the Click
Prerendering makes navigation feel instant by loading the page before the click. It also runs that page, and pays for visits that never happen. Both matter.
Performance
Server-Timing: Making Backend Time Visible in the Browser
A client can measure how long the server took but never what it did. Server-Timing carries the breakdown to the browser and opens the largest interval in a load.
Security
MTA-STS and TLS-RPT: The Control That Can Stop Mail
SPF and DMARC change how mail is classified; MTA-STS changes whether it is delivered. Roll it out with TLS-RPT first, and know what enforce mode really costs.
HTTP
HTTP 413 Request Entity Too Large: Which Layer Rejected It
Five components each enforce their own body-size limit, and one of them returns an empty form instead of a 413. Find the narrowest gate before editing configs.
Networking
ERR_TUNNEL_CONNECTION_FAILED: The Proxy Refused Your CONNECT
The tunnel is a CONNECT request to a forward proxy. Read what the proxy answers, and learn the one server-side setting that causes this for corporate users.