Path MTU Probe

Send HyperText Transfer Protocol (HTTP) requests with custom method, headers, body, and authentication — inspect the full response.

Load a Uniform Resource Locator (URL) in headless Chromium and stream every fetched resource with size and timing.

The simplest possible check: fetch the page, confirm it returns 2xx.

Test any Uniform Resource Locator (URL) for Cross-Origin Resource Sharing (CORS) with a custom method, headers, and body — see exactly why a browser would allow or block the request.

Crawl a website and find broken internal links — renders JavaScript (JS) pages with a headless browser.

Check an IPv4 address against 49 major Domain Name System (DNS) blacklists (Spamhaus, SORBS, Barracuda, SpamCop, etc.).

Continuous traceroute with per-hop loss and Round-Trip Time (RTT) statistics.

Trace the path packets take to a destination host, hop by hop.

Ping many hosts in parallel and report which are alive.

Send Internet Control Message Protocol (ICMP) echo requests and report round-trip time (RTT) and packet loss.

Resolve a domain or Internet Protocol (IP) address to its city, country, Autonomous System Number (ASN)/org, and coordinates — with a map.

Convert IPv4 to/from IPv4-mapped IPv6 (::ffff:a.b.c.d).

Look up a Media Access Control (MAC) address's first 3 octets in the IEEE Organizationally Unique Identifier (OUI) vendor database (curated subset).

One-click domain scorecard — Blacklist, Mail Server, Web Server, and Domain Name System (DNS) checks graded Errors / Warnings / Passed, MXToolbox-style.

Consolidated Mail Exchange (MX), Sender Policy Framework (SPF), Domain-based Message Authentication, Reporting & Conformance (DMARC), and DomainKeys Identified Mail (DKIM)-selector lookup for an email domain.

Look up and validate a domain's Sender Policy Framework (SPF) Text (TXT) record.

Resolve a domain's Mail Exchange (MX) hosts to Internet Protocol (IP) addresses and check each against 49 IP blacklists plus the domain itself against 9 domain blacklists.

Connect to a Simple Mail Transfer Protocol (SMTP) server, capture its banner + EHLO capabilities, and test STARTTLS.

Check Transmission Control Protocol (TCP) port reachability; optionally send a payload and read the reply.

Inspect a server's Transport Layer Security (TLS) handshake: version, cipher, Application-Layer Protocol Negotiation (ALPN), full cert chain.

Probe a list of hostnames (max 16) for HyperText Transfer Protocol (HTTP) and HyperText Transfer Protocol Secure (HTTPS) availability.

Send N HyperText Transfer Protocol (HTTP) HEAD requests to a Uniform Resource Locator (URL) and report min/median/mean/max/stddev latency. From this server's vantage.

Break a Classless Inter-Domain Routing (CIDR) block into network, broadcast, mask, wildcard, and usable host range.

Verbose subnet calculator with address classification flags.

Look up the announcing Autonomous System Number (ASN), covering prefix, country, and Autonomous System (AS) neighbours for a public Internet Protocol (IP) via RIPEstat.

Generate router prefix-list and AS-path filters from IRR data.

Probe which Transport Layer Security (TLS) protocol versions a server accepts and show the cipher each negotiates.

Full chain validation, Online Certificate Status Protocol (OCSP) stapling, Signed Certificate Timestamp (SCT) count, and per-Transport Layer Security (TLS)-version cipher matrix.

Days remaining before a server's Transport Layer Security (TLS) certificate (and its full chain) expires.

Search Certificate Transparency logs for every Secure Sockets Layer (SSL) certificate ever issued to a domain — reveals subdomains, issuers, and historical issuance.

Query a public Network Time Protocol (NTP) server: stratum, offset, round-trip, ref-id, root delay/dispersion. Does not change the system clock.

Fetch a server's SSH version banner and host public keys (Ed25519, ECDSA, RSA) with fingerprints. No authentication.

Negotiate HTTP/2 via Application-Layer Protocol Negotiation (ALPN) and decode the server's SETTINGS frame (window size, max streams, etc.).

Send a WebSocket Upgrade handshake and verify the Sec-WebSocket-Accept response, subprotocols, and extensions.

Benchmark HTTP/2 server performance — measure requests per second, latency distribution, and concurrent stream throughput under sustained load.

Convert UTF-8 text to a hex string, or parse a hex string back to text (separators :/.- ignored).

Convert UTF-8 text to 8-bit binary, or parse a binary string back to text.

Convert text between common casings: UPPER, lower, Title, snake_case, kebab-case, camelCase.

Convert a number between decimal, binary, octal, and hexadecimal representations.

Convert between Unix epoch seconds and International Organization for Standardization (ISO)/Request for Comments (RFC) datetime formats (Coordinated Universal Time (UTC)).

Convert between dotted IPv4 notation, 32-bit decimal, hex, and dotted binary.

Decode a JSON Web Token (JWT) into its header and payload (no signature verification — that needs the signing key).

Compute the cryptographic hash of UTF-8 text using MD5, SHA-1, SHA-256, SHA-384, or SHA-512.

Compute a Hash-based Message Authentication Code (HMAC) of a message using a shared key and a chosen hash algorithm.

Days remaining before a domain's registration expires.

Days remaining before a domain's Resource Record Signatures (RRSIGs) — the cryptographic signatures used by Domain Name System Security Extensions (DNSSEC) — expire.