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DNS, SSL & Network Troubleshooting Guides

The fix for the error on your screen, the DNS server addresses that work, and how to secure email and websites: written by the founder and tested with our own tools.

Most read in English

  1. 01ERR_QUIC_PROTOCOL_ERROR: Meaning & Fix in Chrome and EdgeTroubleshooting8 min read
  2. 02What Is Private DNS? Meaning, Hostname List & SetupDNS11 min read
  3. 03ERR_SSL_PROTOCOL_ERROR: Fix It in Chrome, Edge & LocalhostTroubleshooting11 min read

Latest

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  1. Updated.si Domain Price: Cheapest Registrars Compared (Oct 2026)
  2. Updated.si vs .ai Domain: Price, SEO & Which to Choose (2026)
  3. UpdatedIPv4 vs IPv6: Key Differences, Speed Test & Which to Use
  4. UpdatedWhat Is a DNS Server? How It Works, Types & Examples
  5. UpdatedCloudflare DNS Servers: 1.1.1.1, 1.0.0.1 & IPv6 Setup
  6. Updated400 Bad Request: What It Means & How to Fix It

Fix an error

Find the exact message your screen shows. Every guide names the browser and system it was tested on, and the tool that checks it.

All 38 troubleshooting guides

Chrome & Edge errors16

ERR_ADDRESS_UNREACHABLE Fix for Router, Mac & Android11 minERR_CACHE_MISS Fix It in Chrome, Edge, Android & WebView9 minERR_CERT_AUTHORITY_INVALID Fix in Chrome, Edge & Android9 minERR_CONNECTION_CLOSED What It Means & How to Fix It10 minERR_CONNECTION_REFUSED Meaning & Fix (Chrome, All Browsers)11 minERR_CONNECTION_RESET What It Means & How to Fix It11 minERR_CONNECTION_TIMED_OUT & ERR_TIMED_OUT: Causes and Fixes11 minERR_EMPTY_RESPONSE What It Means & How to Fix It11 minERR_HTTP2_PROTOCOL_ERROR Meaning & Fix in Chrome and Edge11 minERR_NAME_NOT_RESOLVED (-105): Meaning & Fix in Chrome8 minERR_NETWORK_CHANGED What It Means & How to Fix It10 minERR_QUIC_PROTOCOL_ERROR Meaning & Fix in Chrome and Edge8 minERR_SSL_PROTOCOL_ERROR Fix It in Chrome, Edge & Localhost11 minERR_SSL_VERSION_OR_CIPHER_MISMATCH Fix in Chrome & Edge7 minERR_TOO_MANY_REDIRECTS How to Fix It (All Browsers)11 minERR_TUNNEL_CONNECTION_FAILED What It Means & How to Fix It9 min

HTTP status codes11

400 Bad Request: What It Means & How to Fix It10 min401 Unauthorized & 401 Authorization Required: How to Fix13 min403 Forbidden Error: What It Means & How to Fix It12 min405 Method Not Allowed: What It Means & How to Fix It8 minHTTP Error 429 Too Many Requests: Meaning & Fix10 minHTTP 500 Internal Server Error: Causes & Fix (nginx, Apache)11 min502 Bad Gateway: What It Means & How to Fix It12 min503 Service Unavailable: What It Means & How to Fix It9 min504 Gateway Time-out: What It Means & How to Fix It10 minCloudflare Error 520: What It Means & How to Fix It10 minHTTP 302 Status Code: What It Means & 302 vs 30110 min

DNS & connection8

DNS_PROBE_FINISHED_NXDOMAIN What It Means & How to Fix It10 minDNS_PROBE_STARTED Meaning & Fix on Chrome, Android, Windows8 min"This Network Is Blocking Encrypted DNS Traffic" Fix10 minDNS Server Unavailable: What It Means & How to Fix It9 minHow to Fix DNS Server Not Responding (Step-by-Step)8 minHow to Fix Slow DNS Lookup in Chrome, Windows & Mac9 minHow to Flush DNS: Windows, Mac, Linux, Fedora & Chrome8 minWiFi Connected But No Internet? 10 Fixes That Work10 min

Certificates, Firefox & other4

Connection Is Not Private Fix It on iPhone, iPad & Chrome11 minPR_CONNECT_RESET_ERROR in Firefox: Causes & How to Fix It9 minX-Frame-Options Fix “Refused to Connect” in an iframe12 minHow to Test a Public API Endpoint: DNS, TLS, Headers & CORS10 min

DNS servers & setup

Addresses, Private DNS hostnames and setup for every device, with our own speed and filter tests.

All 12 DNS guides
Cloudflare1.1.1.11.0.0.1Cloudflare DNS Servers: 1.1.1.1, 1.0.0.1 & IPv6 SetupUpdated Oct 2711 minAdGuard DNSTested by us94.140.14.1494.140.15.15AdGuard DNS Servers: 94.140.14.14, Private DNS & SetupOct 2612 minCleanBrowsingTested by us185.228.168.168185.228.169.168CleanBrowsing DNS: Family Filter IPs, Setup & Test ResultsOct 2612 minNextDNSNextDNS is a DNS firewall you configure yourself, free for 300,000 queries a month. Set it up on Android, iPhone, Windows or a router and check that it works.NextDNS Setup: Free Limit, Every Device & Best SettingsOct 2612 minQuad9Tested by us9.9.9.9149.112.112.112Quad9 DNS Servers: 9.9.9.9 IPs, IPv6 & Setup GuideOct 2612 minGoogle Public DNS8.8.8.88.8.4.4Google DNS: 8.8.8.8, 8.8.4.4, IPv6 Addresses & SetupUpdated Oct 2612 minAT&T68.94.156.168.94.157.1AT&T DNS Servers (68.94.156.1) & How to Change ThemUpdated Oct 2610 minComcast / Xfinity75.75.75.7575.75.76.76Comcast / Xfinity DNS Servers (75.75.75.75) & How to ChangeUpdated Oct 2610 minVerizon Fios71.252.0.12by regionVerizon Fios DNS Servers by Region & How to Change ThemUpdated Oct 269 minSpectrum71.10.216.171.10.216.2Spectrum DNS Servers (71.10.216.1) & How to Change ThemUpdated Oct 2610 minDNS Speed TestA DNS server turns domain names into IP addresses. See how one resolves a name step by step, the 4 types of DNS servers, how to find yours and which to use.What Is a DNS Server? How It Works, Types & ExamplesUpdated Oct 2711 minDNS Leak TestPrivate DNS encrypts the site names your phone looks up, so your network and ISP can't read them. What it means, the hostname to type, and setup on any device.What Is Private DNS? Meaning, Hostname List & SetupUpdated Oct 2611 min

Guides & how-tos

Step-by-step guides and comparisons, each ending in the tool that proves the result.

All 22 guides
Spamhaus Blacklist Removal: Check & Delist an IP or DomainCheck if Spamhaus lists your IP or domain, what SBL, XBL, CSS, PBL and DBL listings mean, how to get delisted for free, and why 1.1.1.1 can't check it.GuidesOct 2612 minIP Blacklist CheckWHOIS Lookup Guide: Find Who Owns a Domain & Read the RecordHow to do a WHOIS lookup: run it online or from the command line, read every field and status code, get past REDACTED FOR PRIVACY, and why RDAP replaced WHOIS.GuidesUpdated Oct 2716 minWHOIS LookupTracert Command: How to Traceroute on Windows, Mac & LinuxHow to use tracert on Windows and traceroute on Mac and Linux: the syntax, the options that matter, example output, and how to read timeouts and latency jumps.GuidesUpdated Oct 2712 minTraceroute
.si Domain Price: Cheapest Registrars Compared (Oct 2026)Updated Oct 279 min.si vs .ai Domain: Price, SEO & Which to Choose (2026)Updated Oct 2710 minIPv4 vs IPv6: Key Differences, Speed Test & Which to UseUpdated Oct 2711 minHow to Generate a QR Code (Free): Types, Sizes and LogosUpdated Oct 2715 minWhat Is a MAC Address? How to Find It on Any DeviceUpdated Oct 2712 min.si Domain: Country, Rules, Price & Why It's TrendingUpdated Oct 2611 minBest Vibe Coding Tools in 2026: 10 AI App Builders ComparedSep 3016 minBest Website Builder in 2026: 10 Builders Compared by JobSep 3013 minCan AI Make My Portfolio? Yes: How to Build One in an Hour (With Prompts)Sep 3011 minContent Calendar Template: Free Layout, Columns and a 30-Day ExampleSep 3011 minFleet Management Dashboard: 12 KPIs to Track and How to Build OneSep 3013 minFree Portfolio Website Templates: 15 Genuinely Free Options (2026)Sep 3012 minHow to Create a Social Media App in 2026: Features, Stack, Cost and LaunchSep 3013 minHow to Start a Medical Transport Business (NEMT) in 2026Sep 3015 minResume Website Template: Free HTML Layout and How to Publish ItSep 3010 minVibe Coding Apps: Beginner's Guide and 8 Apps You Can Build This WeekendSep 3013 minTitan Email: Plans, Prices & DNS Setup (MX, SPF, DKIM)Sep 2610 minBest OpenClaw Hosting in 2026: 7 VPS Options ComparedAug 1810 minHow to Install OpenClaw on a VPS (Docker & npm Guide)Aug 1811 min

Hosting & domain reviews

All 6
A2 Hosting Black Friday 2026: Hosting.com Deal & PricesOct 2611 minA2 Hosting (Hosting.com) vs Hostinger: 2026 ComparisonSep 299 minHosting.com Pricing 2026: Every Plan & Renewal PriceSep 2911 minHosting.com Reseller Hosting: Enhance vs cPanel (2026)Sep 299 minHosting.com Coupon (A2 Hosting): Up to 86% Off, No CodeSep 269 minVerpex Hosting Review 2026: Plans, Pricing & VerdictAug 1810 min

Explainers

All 3
HTTP 302 Status Code: What It Means & 302 vs 301Updated Oct 2610 minWhat Is a Landing Page? Definition, Types, Anatomy and ExamplesSep 3012 minA2 Hosting Is Now Hosting.com: What Changed (2026)Sep 268 min

Security

All 2
Web Security Best Practices: A Layer-by-Layer Guide (2026)Updated Oct 2732 minWhat Is an SSL Certificate Chain? Order, Check & FixUpdated Oct 2711 min

Every guide ends in a tool

Check it yourself

Each guide links the free tool we built for the same problem, so you can run the check it describes on your own domain or connection. These are the tools these guides use most.

All 50+ tools

About the author

Shaik Vahid Founder of DNS Robot

Vahid spent years in web hosting support fixing domains, DNS records, SSL certificates and email delivery for customers. He builds DNS Robot's tools and writes these guides from the errors people actually hit.