# sysadmin.lk > Free online DNS, email authentication, SSL/TLS, network, website and security diagnostics, plus Linux, Kubernetes, JSON and XML utilities for sysadmins and DevOps engineers. No account is needed for any lookup, and every network check is also a JSON API. Each check runs server-side and explains what was checked, what was found, why it matters and how to fix it. Scores follow published rules: https://sysadmin.lk/methodology ## Start here - [Super Scanner](https://sysadmin.lk/scanner): runs 24 DNS, email, website, TLS and reputation checks on a domain and returns one 0-100 score. - [All tools](https://sysadmin.lk/tools): every tool on one page. - [Scoring methodology](https://sysadmin.lk/methodology): how the Super Scanner score, SSL grade and deliverability score are calculated. - [Full tool guides](https://sysadmin.lk/llms-full.txt): every tool's explanation, examples and FAQ as one Markdown file. ## Developer Utilities [Developer Utilities overview](https://sysadmin.lk/utilities) - [Base64 Encoder / Decoder](https://sysadmin.lk/utilities/base64): Encode text to Base64 or decode it back - [URL Encoder / Decoder](https://sysadmin.lk/utilities/url-encoder): Percent-encode or decode URL and query-string text - [HTML Entity Encoder / Decoder](https://sysadmin.lk/utilities/html-entities): Escape text to HTML entities or decode them back - [Hash Generator](https://sysadmin.lk/utilities/hash-generator): MD5, SHA-1, SHA-256, SHA-384 & SHA-512 of any text - [.htpasswd Generator](https://sysadmin.lk/utilities/htpasswd-generator): Basic-auth user:hash lines (apr1 / SHA-1) - [QR Code Generator](https://sysadmin.lk/utilities/qr-generator): Encode a link or text as an SVG/PNG QR code - [Password Generator](https://sysadmin.lk/utilities/password-generator): Generate a strong, random password - [UUID / GUID Generator](https://sysadmin.lk/utilities/uuid-generator): Generate one or many random v4 UUIDs - [JWT Decoder](https://sysadmin.lk/utilities/jwt-decoder): Decode a JWT's header, payload, and expiry - [JWT Generator](https://sysadmin.lk/utilities/jwt-generator): Build and HMAC-sign an HS256/384/512 token - [Regex Tester](https://sysadmin.lk/utilities/regex-tester): Test a regular expression with live matches and groups - [Text Diff](https://sysadmin.lk/utilities/text-diff): Compare two blocks of text line by line - [Unix Timestamp Converter](https://sysadmin.lk/utilities/timestamp-converter): Convert Unix timestamps to and from dates - [Password Breach Checker](https://sysadmin.lk/utilities/password-breach-checker): Check a password against known data breaches - [Nginx / Apache Config Generator](https://sysadmin.lk/utilities/webserver-config): Generate a reverse-proxy or static-site vhost config ## Network Tools [Network Tools overview](https://sysadmin.lk/network) - [Ping](https://sysadmin.lk/network/ping): Latency and packet loss - [Traceroute](https://sysadmin.lk/network/traceroute): Hop-by-hop network path - [Port Checker](https://sysadmin.lk/network/port-checker): Common TCP ports - [IP Lookup](https://sysadmin.lk/network/ip-lookup): PTR, ASN, WHOIS/RDAP - [Subnet Calculator](https://sysadmin.lk/network/subnet-calculator): CIDR, netmask, and host range ## DNS Lookup Tools [DNS Lookup Tools overview](https://sysadmin.lk/dns) - [A Record](https://sysadmin.lk/dns/a): IPv4 address for a domain - [AAAA Record](https://sysadmin.lk/dns/aaaa): IPv6 address for a domain - [CNAME Record](https://sysadmin.lk/dns/cname): Domain alias lookup - [MX Record](https://sysadmin.lk/dns/mx): Mail servers for a domain - [NS Record](https://sysadmin.lk/dns/ns): Authoritative nameservers - [TXT Record](https://sysadmin.lk/dns/txt): Arbitrary text records - [SOA Record](https://sysadmin.lk/dns/soa): Zone authority details - [CAA Record](https://sysadmin.lk/dns/caa): Authorized certificate issuers - [Propagation Checker](https://sysadmin.lk/dns/propagation): Check a record across global resolvers - [WHOIS Lookup](https://sysadmin.lk/dns/whois): Registrar, creation/expiry dates, and nameservers - [DNSSEC Checker](https://sysadmin.lk/dns/dnssec): Check DNSSEC signing and chain-of-trust validation - [RDNS Lookup](https://sysadmin.lk/dns/rdns): Reverse DNS (PTR) lookup for an IP address - [SRV Record](https://sysadmin.lk/dns/srv): Service records (priority, weight, port, target) - [DS Record](https://sysadmin.lk/dns/ds): DNSSEC delegation signer records at the parent zone - [Zone Transfer Test](https://sysadmin.lk/dns/zone-transfer): Check whether nameservers allow an AXFR transfer ## Email Authentication & Deliverability Tools [Email Authentication & Deliverability Tools overview](https://sysadmin.lk/email) - [SPF Checker](https://sysadmin.lk/email/spf): Validate SPF syntax and the 10-lookup limit - [DKIM Checker](https://sysadmin.lk/email/dkim): Look up and validate a DKIM key by selector - [DMARC Checker](https://sysadmin.lk/email/dmarc): Check DMARC policy, alignment and reporting - [BIMI Checker](https://sysadmin.lk/email/bimi): Brand indicators for email - [MTA-STS Checker](https://sysadmin.lk/email/mta-sts): Enforced TLS mail delivery - [TLS-RPT Checker](https://sysadmin.lk/email/tls-rpt): SMTP TLS reporting - [Deliverability Test](https://sysadmin.lk/email/deliverability-test): Send a test email, get a 0-10 score - [SMTP Test](https://sysadmin.lk/website/smtp-test): Connect, STARTTLS, log in and send through an SMTP server - [Header Analyzer](https://sysadmin.lk/email/header-analyzer): Parse a received email's headers, auth results, and hop delays - [SPF Record Generator](https://sysadmin.lk/email/spf-generator): Build an SPF record with a 10-lookup check - [DMARC Record Generator](https://sysadmin.lk/email/dmarc-generator): Build a DMARC policy record from your settings - [DKIM Key Generator](https://sysadmin.lk/email/dkim-generator): Generate an RSA key pair and DKIM DNS record ## Website & HTTP Tools [Website & HTTP Tools overview](https://sysadmin.lk/website) - [HTTP Checker](https://sysadmin.lk/website/http): Response, timing, redirects - [Security Headers](https://sysadmin.lk/website/security-headers): HSTS, CSP, and more ## SSL/TLS & Security Tools [SSL/TLS & Security Tools overview](https://sysadmin.lk/security) - [SSL/TLS Checker](https://sysadmin.lk/security/ssl): Certificate chain, expiry, protocol and an A+ to F grade - [CSR & Key Generator](https://sysadmin.lk/security/csr-generator): Generate a CSR and private key to buy an SSL certificate - [Blacklist Checker](https://sysadmin.lk/security/blacklist): DNSBL reputation lookup - [Subdomain Takeover](https://sysadmin.lk/security/takeover): Dangling CNAME detection - [security.txt Generator](https://sysadmin.lk/security/security-txt): Build or validate an RFC 9116 security.txt - [Certificate Decoder](https://sysadmin.lk/security/cert-decoder): Read a PEM X.509 certificate's details - [HSTS Preload Checker](https://sysadmin.lk/security/hsts-preload): Check HSTS header against preload-list requirements ## Linux Tools for Sysadmins [Linux Tools for Sysadmins overview](https://sysadmin.lk/linux) - [Linux Commands Cheat Sheet](https://sysadmin.lk/linux/commands): Searchable reference of everyday Linux commands with examples - [Crontab Generator](https://sysadmin.lk/linux/crontab-generator): Build a cron expression and preview its next run times - [SAR Report Analyzer](https://sysadmin.lk/linux/sar-analyzer): Visualize CPU, memory, load, and network from sar -A ## Kubernetes YAML Tools [Kubernetes YAML Tools overview](https://sysadmin.lk/kubernetes) - [Manifest Generator](https://sysadmin.lk/kubernetes/manifest-generator): Generate Deployment, Service, Ingress, and more - [Secret Encoder / Decoder](https://sysadmin.lk/kubernetes/secret-encoder): Base64 key/value pairs into a Secret, or decode one - [kubeconfig Validator](https://sysadmin.lk/kubernetes/kubeconfig-validator): Check clusters, users, and contexts resolve - [RBAC Generator](https://sysadmin.lk/kubernetes/rbac-generator): Role / ClusterRole plus binding YAML ## XML Tools [XML Tools overview](https://sysadmin.lk/xml) - [XML Formatter](https://sysadmin.lk/xml/formatter): Pretty-print messy XML - [XML Validator](https://sysadmin.lk/xml/validator): Check XML well-formedness - [XML Minifier](https://sysadmin.lk/xml/minifier): Strip whitespace and comments - [XML ↔ JSON Converter](https://sysadmin.lk/xml/json-converter): Convert between XML and JSON - [XML → YAML Converter](https://sysadmin.lk/xml/yaml-converter): Convert XML to YAML - [XML → CSV Converter](https://sysadmin.lk/xml/csv-converter): Extract tabular XML data - [XML → XSD Generator](https://sysadmin.lk/xml/xsd-generator): Infer a schema from sample XML - [XSD Validator](https://sysadmin.lk/xml/xsd-validator): Validate XML against an XSD - [XPath Tester](https://sysadmin.lk/xml/xpath-tester): Test XPath expressions against XML - [XML Diff](https://sysadmin.lk/xml/diff): Compare two XML documents - [XML Escape / Unescape](https://sysadmin.lk/xml/escape): Encode/decode XML entities - [XML Sitemap Generator](https://sysadmin.lk/xml/sitemap-generator): Build a sitemap.xml ## JSON Tools [JSON Tools overview](https://sysadmin.lk/json) - [JSON Formatter](https://sysadmin.lk/json/formatter): Pretty-print messy JSON - [JSON Validator](https://sysadmin.lk/json/validator): Check JSON syntax - [JSON Minifier](https://sysadmin.lk/json/minifier): Strip whitespace from JSON - [JSON ↔ YAML Converter](https://sysadmin.lk/json/yaml-converter): Convert between JSON and YAML - [JSON ↔ CSV Converter](https://sysadmin.lk/json/csv-converter): Convert between a JSON array and CSV - [JSON Escape / Unescape](https://sysadmin.lk/json/escape): Escape text for a JSON string, or decode it - [JSONPath Tester](https://sysadmin.lk/json/jsonpath-tester): Evaluate a JSONPath expression against JSON - [JSON Schema Validator](https://sysadmin.lk/json/schema-validator): Validate JSON against a JSON Schema - [JSON Diff](https://sysadmin.lk/json/diff): Compare two JSON documents by structure - [JSON → Code](https://sysadmin.lk/json/to-code): Generate TypeScript, Go, or Python types ## API - [OpenAPI 3 description](https://sysadmin.lk/openapi.json): the public diagnostic endpoints, machine-readable. - [Developer documentation](https://sysadmin.lk/developers): authentication, rate limits and response envelope. ## Optional - [Blog](https://sysadmin.lk/blog): tutorials on Linux, networking, Kubernetes, DNS and email infrastructure. - [About](https://sysadmin.lk/about): built and maintained by Prabath Thalangama. - [Privacy](https://sysadmin.lk/privacy): what is and isn't stored.