Twenty seven checkers for uptime, certificates, DNS and email records, status codes and log patterns. No sign-up, and fourteen of them never send your input anywhere.
Showing 27 tools
Check SSL certificate validity, expiration calculation, and chain validation. Get alerted before your certificate expires.
Check SSL certificate status, expiry, and issuer for multiple domains at once. Export results to CSV for easy reporting.
Check if a specific port is open on an IP or domain. Useful for verifying firewall rules and service reachability.
Measure TCP connection latency to any server. Check reachability and response time instantly.
Is it down? Check the HTTP status of any website. Get response codes, time, and downtime alerts instantly.
Perform advanced DNS lookups for specific record types (A, MX, TXT, CNAME, NS, SOA) using a real command-line style output.
Check DNS records across multiple global servers to verify propagation status after making changes to your domain configuration.
Check if an IP address or domain is listed on major email blacklists (DNSBL) like Spamhaus, Barracuda, and Sorbs.
Analyze and validate SPF records to ensure email deliverability. Detect syntax errors and potential security issues.
Check the HTTP status code for one URL, or up to 10 at once in the bulk checker. Explanations, response headers, and the full redirect chain for debugging APIs and websites.
Parse cron expressions into human-readable format and generate cron schedules visually. Calculate next execution times and visualize schedules.
Test and validate XPath and CSS selectors instantly against live websites or HTML snippets. Get intelligent suggestions for robust selectors.
Format, validate, compare, minify, and generate JSON Schema entirely in your browser. Includes JSONPath click-to-copy, line numbers, and error location reporting.
Test JavaScript regular expressions with real-time match highlighting, capture groups, replace preview, a built-in pattern library, and a regex cheatsheet.
Convert Unix timestamps to human-readable dates and vice versa. Calculate time differences, work with multiple timezones, and add/subtract time from timestamps.
Decode and validate JWT tokens instantly in your browser. View header, payload, check expiration, and validate claims. 100% client-side and secure.
Convert between JSON, CSV, and XML formats instantly. 100% client-side with advanced options for flattening, formatting, and customization. Free forever.
Decode SSL/TLS error codes like ERR_SSL_PROTOCOL_ERROR instantly. Get plain-English explanations, common causes, and step-by-step fixes.
Scan any website's HTTP security headers (HSTS, CSP, X-Frame-Options) and get an instant A-F security grade with actionable recommendations.
Generate a tailored pre-deployment checklist for your stack. Covers build, tests, security, infrastructure, monitoring, and rollback. Export as markdown.
Test your API endpoint security instantly. Check CORS policy, authentication, rate limiting, server info leakage, and more.
Paste your GitHub Actions or GitLab CI config and get instant validation. Detects misconfigurations, hardcoded secrets, and missing best practices.
Test your Kubernetes readiness and liveness probe endpoints. Verify HTTP status, response time, and response body before deploying.
Test regex patterns against log samples. See matches highlighted with captured groups. Includes Apache, Nginx, and JSON log samples.
Inspect webhook payloads, validate JSON structure, check timestamps, verify signatures, and detect common issues.
Generate a structured incident response template with timeline, impact assessment, root cause analysis, and post-mortem sections.
Convert an SLA percentage into allowed downtime per day, week, month, quarter, and year. Includes a common-tiers reference table and nines terminology.
ObserveOne provides automated testing, monitoring, and observability for your entire stack. Run tests 24/7, get instant alerts, and ship with confidence.
Most people arrive here with a symptom rather than a tool name. This table maps the symptom to the check that settles it, and says what the check gives back.
| What you are seeing | Use | What it tells you |
|---|---|---|
| A site will not load and you do not know if it is only you | Website status checker | The HTTP status code and response time seen from outside your network. |
| A request returns a code you did not expect | HTTP status code checker | The code, the response headers and the full redirect chain. |
| The browser warns that a certificate is expired or untrusted | SSL and TLS expiry checker | Expiry date, issuer and whether the chain validates. |
| You need the same certificate answer for a list of domains | Bulk SSL checker | Status, expiry and issuer for every domain, exportable as CSV. |
| A browser shows an SSL error code and no explanation | SSL error decoder | What the code means, the usual causes, and what to change. |
| Mail you send is landing in spam | SPF record checker | Syntax errors and lookup problems in the published SPF record. |
| Mail is rejected outright and you suspect the sending IP | IP blacklist monitor | Whether the address appears on the major DNSBL lists. |
| A DNS change does not seem to have taken effect | DNS propagation checker | The answer several resolvers around the world currently give. |
| You need one record type resolved and read properly | DNS record lookup | A, MX, TXT, CNAME, NS and SOA records in dig-style output. |
| A service is unreachable and you suspect a firewall rule | Open port checker | Whether the port accepts a connection from outside. |
| You want to know what an endpoint gives away | API security tester | CORS policy, authentication, rate limiting and server headers. |
| You need allowed downtime for an SLA percentage | SLA and uptime calculator | Permitted downtime per day, week, month, quarter and year. |
Fourteen of these tools only transform text you paste, and they make no network request at all. A JWT, a log sample, a CI config or a JSON payload stays on your machine: the JSON formatter, the JSON, CSV and XML converter, the JWT decoder, both regex testers, the XPath and CSS selector tester, the cron parser, the Unix timestamp converter, the SLA and uptime calculator, the SSL error decoder, the CI/CD pipeline validator, the webhook debugger, the deployment checklist generator and the incident response template.
The other thirteen check a live host, so the request is made from our network rather than yours. That is not a design preference. A page in a browser can only speak HTTP, and cross-origin requests are limited by the target site's CORS policy, so reading another domain's certificate chain, opening a TCP port or asking a DNS resolver directly are all outside what browser code is allowed to do.
Running server side has a second effect. The answer you get is what a machine outside your network sees, not what your machine sees. If a check reports a host as reachable and you still cannot load it, the fault sits between you and the host: a stale DNS entry, a VPN, a proxy, or ISP routing.
No. Every tool on this page runs without a sign-up, a key or an email address.
For the fourteen tools that only transform text you paste, no. They make no network request at all, so a token, a log line or a JSON payload never reaches our servers. The thirteen tools that check a live host have to make the request from our network, because a browser cannot open a raw socket or read another site's certificate chain.
A page in a browser can only make HTTP requests, and cross-origin requests are limited by the target site's CORS policy. Reading a certificate chain, opening a TCP port or querying a DNS resolver directly are all outside what a page is allowed to do, so those checks run server side.
For the server-backed checks it is what a machine outside your network sees. That is the point of asking a third party. If a check reports a site as up and you still cannot reach it, the problem is between you and the site rather than at the site itself.
No. They answer a question once, when you press the button. Continuous checks on a schedule, with alerting and history, are what the ObserveOne product does.
Twenty seven. They cover uptime and HTTP, SSL and TLS, DNS and email records, security scanning, and text and format conversion.