Network Tools Online for when something on the web is not answering
Ping a host, check a port, resolve DNS, read response headers, inspect a certificate, look up WHOIS and find broken links. The tools you reach for between it works and it does not.
7 tools here, 150+ across the site
$ dig convertnow.tools +short
104.21.44.12
$ curl -I https://convertnow.tools
HTTP/2 200 · strict-transport-security: max-age=31536000
All tools
Broken Link CheckerScan a URL for broken or dead linksNetwork & Web
Domain Age CheckerFind out when a domain was first registeredNetwork & Web
Page Speed AnalyzerTest page load time and get actionable improvement tipsNetwork & Web
Ping ToolTest connectivity and response time to any hostNetwork & Web
Port CheckerCheck if a specific port is open on a serverNetwork & Web
Website Screenshot ToolCapture a full-page screenshot of any URLNetwork & Web
Whois LookupCheck domain registration details and ownership infoNetwork & Web
the journey
Five things that happen between a click and a page
When a site fails to load, it failed at one of these. Knowing which one narrows the problem immediately, and each tool here probes a different step.
STEP 1DNS resolutionThe name becomes an IP address. Fails when a record is missing, misconfigured or still propagating. Probe it with the DNS lookup tool.
STEP 2ReachabilityPackets have to get there and back. Ping measures round trip time and whether the host answers at all.
STEP 3Port openThe right service must be listening. A closed 443 means TLS never starts, regardless of DNS being perfect.
STEP 4TLS handshakeCertificate must be valid, unexpired, and match the hostname. The certificate checker reads the whole chain.
STEP 5HTTP responseOnly now does the server return a status code and headers. The header checker reads what came back.
Work through them in order. It sounds obvious and it saves an enormous amount of time, because a certificate error and a DNS error produce similar looking browser messages while requiring completely different fixes.
http status
The status codes worth recognising on sight
The first digit tells you who has the problem. Two hundred is success, three hundred is redirection, four hundred is your request, five hundred is their server.
200OK. The request succeeded and the body is the answer.
301Moved permanently. Passes ranking signals to the new URL. The one to use for a real move.
302Found, temporary. Search engines keep the old URL indexed. Using this for a permanent move is a common SEO error.
304Not modified. Your cached copy is still good, so no body is sent. Good for performance.
401Unauthorised. You have not authenticated. Confusingly named, since it means unauthenticated.
403Forbidden. You authenticated fine and still may not have it.
404Not found. Nothing at this URL. The broken link checker hunts for these.
429Too many requests. You are being rate limited. Back off and check for a Retry-After header.
500Internal server error. Something broke server side and it did not say what.
502Bad gateway. A proxy got an invalid response from upstream. Very common behind a CDN.
503Service unavailable. Overloaded or in maintenance. Usually temporary by design.
504Gateway timeout. Upstream took too long to answer.
The full registry lives in RFC 9110, which replaced the older 7231. Worth knowing that a 200 with an error message in the body is a real and common antipattern, so checking the code alone is not always enough.
dns records
The record types you will actually meet
DNS holds far more than addresses. These are the ones that come up when something is broken.
| Type | Holds | Breaks when |
|---|---|---|
| A | An IPv4 address for a name | Missing or pointing at an old server after a migration |
| AAAA | An IPv6 address | Present but pointing somewhere dead, so IPv6 clients fail while IPv4 works |
| CNAME | An alias to another name | Set on a root domain, which the spec does not allow. Providers offer ALIAS or ANAME instead. |
| MX | Mail servers and their priority | Missing, so mail bounces while the website works perfectly |
| TXT | Arbitrary text, used for SPF, DKIM and domain verification | Two SPF records exist, which is invalid and fails the check silently |
| NS | Which nameservers are authoritative | Registrar and DNS host disagree, so changes appear to do nothing |
| CAA | Which certificate authorities may issue for the domain | Set too narrowly, blocking your own certificate renewal |
TTL is the value that explains most propagation confusion. It tells resolvers how long to cache an answer, so a change to a record with a 24 hour TTL can take a day to appear even though the authoritative server updated instantly. Lower the TTL a day before a planned migration and the cutover becomes far less painful.
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Other categories
Every category on ConvertNow, free and growing.
From the blog
How the web actually moves
DNS, TLS, headers and the hops between a click and a page.
FAQ
Questions about these network tools online
What gets queried, what is public, and how to read the results.
Do these tools actually contact the sites I enter?
Yes, and they have to. Unlike most of this site, a DNS lookup, certificate check, port probe or header read cannot be answered from your own machine. The domain or URL you type is what gets queried, and nothing else about you is attached to it.
Why does DNS show one address while my browser goes somewhere else?
Caching, almost always. Your operating system, your router and your internet provider all cache DNS answers for the duration of the record TTL. A lookup here queries a resolver directly and may see the new value before your browser does.
What is TTL and why do changes take so long?
Time to live tells resolvers how long to cache an answer. A record with a 24 hour TTL can take a full day to propagate even though your authoritative server updated instantly. Lowering the TTL a day before a planned migration makes cutover far less painful.
Why does ping fail on a site that clearly works?
Because many hosts and most CDNs block ICMP echo requests deliberately, to reduce noise and limit reconnaissance. A failed ping means the host did not answer that particular probe, not that the site is down. Check the port or the HTTP response instead.
What does a 502 bad gateway actually mean?
A proxy or CDN in front of the real server got an invalid response from it. The edge is up, the origin is not answering properly. It is one of the most common errors behind a CDN, and it points at the origin rather than at DNS or TLS.
Can I check a page that sits behind a login?
No. These tools make unauthenticated requests, so anything requiring a session will return the login page or a 401 or 403. That is also why the broken link checker cannot see inside a members area.
Do you keep a history of my lookups?
No. Queries run on demand and render straight to the page. Nothing is stored against you, and DNS resolution goes through an encrypted DNS over HTTPS resolver rather than plain port 53, so the query is not readable in transit.
Why does my certificate show as invalid on mobile but fine on desktop?
Usually a missing intermediate certificate. Desktop browsers often cache intermediates from previous visits and fill the gap silently, while a fresh mobile client cannot. The certificate checker shows the full chain, which makes an incomplete one obvious.
Transparency
Explore all tools
What we look up, and where
Unlike most of this site, these tools genuinely have to talk to the network. Here is exactly what that means.
Only the target is sentThe domain, host or URL you type is what gets queried. Nothing else about you or your session is attached to the lookup.
Public data onlyDNS records, response headers, certificate chains and WHOIS entries are all published information. These tools read what any client could read.
DNS over HTTPSResolution goes through an encrypted DoH resolver rather than plain port 53, so the query is not readable in transit.
No results are storedLookups are performed on demand and rendered. Nothing is cached against you or kept after the page closes.