systrex
Tools for the people who keep the network up.
Small, single-purpose utilities for operators. Each one does one job and asks nothing of you: no account, no cookie banner, no upsell. Tools marked local run entirely in your browser, so what you paste never leaves the machine. Tools marked edge answer from the point of presence nearest you, which is the only way a DNS or TLS result means anything.
Network
05- Subnet calculatorNetwork and broadcast address, usable host range, masks, and subnet splitting. IPv4 and IPv6.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- CIDR overlap checkTest a list of prefixes for overlaps, gaps and containment. Built for reviewing allocation tables.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- MTU and MSSWork out MSS from MTU across encapsulation layers, including VXLAN, IPsec and PPPoE overhead.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- ASN lookupFind the autonomous system, organisation and announced prefixes behind an IP address.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
- MAC vendor lookupResolve a MAC address to its OUI registrant.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
DNS
03- DNS lookupQuery A, AAAA, CNAME, MX, NS, TXT, SOA and CAA records from the edge location nearest you.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
- DNS propagationCompare answers from several public resolvers to see where a change has landed.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
- Reverse DNSPTR lookup for an address, and a forward-confirmed check of the result.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
TLS
02- TLS certificate inspectorIssuer, subject, SANs, validity window, days to expiry and the full chain for any host.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
- CSR and certificate decoderPaste a PEM certificate or signing request and read the decoded fields.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
HTTP
03- HTTP traceFollow a redirect chain hop by hop and show the request and response headers at each step.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
- Cache header analyserRead Cache-Control, ETag, Vary and Age, then explain what a shared cache will actually do.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
- Security header checkAudit HSTS, CSP, frame options and referrer policy on a live origin.edge — Runs at the point of presence nearest you, and reports which one answered. Do not put a secret into an edge tool.coming soon — In the catalogue, not yet in service.
Encoding
03- Base64Encode and decode, with URL-safe and raw byte modes.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- JWT decoderRead header and claims, and check expiry. The token never leaves the browser.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- URL parserSplit a URL into its parts and decode percent-encoded query values.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
Time
04- Work timerCountdown for focused work, with break cycling and an alarm that survives a background tab.local — Runs entirely in your browser. What you paste is never transmitted.online — Built and ready to use.
- Cron expression parserExplain a cron line in words and list the next run times in any time zone.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- Timestamp converterConvert between Unix epoch, ISO 8601 and local time, in seconds, milliseconds or nanoseconds.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- Duration converterRead and normalise Go, Prometheus and ISO 8601 duration strings.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
Text
03- YAML and JSONConvert in both directions, with anchor expansion and multi-document support.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- Regex testerTest a pattern against sample text and see every capture group.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- Text diffLine and word level diff for config files and manifests.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
Reliability
02- Error budget calculatorTurn an SLO into allowed downtime and failed requests per window, and show burn rate thresholds.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.
- Percentile calculatorCompute p50 to p99.9 from a pasted set of latency samples, and show the histogram.local — Runs entirely in your browser. What you paste is never transmitted.coming soon — In the catalogue, not yet in service.