SSL Certificate Checker
Check the SSL/TLS certificate currently presented by a public hostname. Review expiration, trust status, issuer, subject, SAN coverage, TLS version, cipher and custom-port details.
Ready to check a certificate
Enter a hostname and port above. Standard HTTPS normally uses port 443.
No Subject Alternative Names were returned.
This page is a browser-based interface, but the live TLS inspection itself must be performed by a network service because browsers do not expose arbitrary remote certificate handshakes to page JavaScript. The hostname and port you enter are sent to the third-party lookup endpoint used by this tool. Do not enter private/internal hostnames or confidential infrastructure names. The page itself may also load interface resources from CDNs and advertising resources from external providers.
Free Online SSL Certificate Checker
The Utiliverse SSL Certificate Checker is a practical browser-based interface for checking the SSL/TLS certificate presented by a public website or other TLS-enabled hostname. It can help you confirm whether a certificate is still valid, how many days remain before expiration, who issued it, which hostname it was issued for, which Subject Alternative Names are covered, and which TLS protocol and cipher were negotiated during the check. These details are useful when diagnosing HTTPS warnings, confirming a renewal, checking a migration, or reviewing the basic certificate status of a server before a problem reaches visitors.
Although people commonly say “SSL certificate,” modern secure web connections use TLS, the successor to the older SSL protocols. The familiar SSL wording remains common in hosting dashboards, search terms, and certificate products, so this tool uses both terms. A successful result does not replace a full security audit: application security, HTTP security headers, revocation behavior, supported cipher suites, legacy-protocol exposure, DNS configuration, server patching, and content security all require separate checks. For a layer-by-layer explanation of hostname mismatch, expiration, trust-chain problems, deployment failures, and HTTP-vs-TLS clues, see the SSL certificates and errors guide.
How to Use the SSL Certificate Checker
Start by entering the public domain name or hostname you want to inspect. You can type a simple hostname such as example.com, a subdomain such as www.example.com, or paste a complete HTTPS URL. The tool removes the URL scheme, path, query string, and fragment so the check is performed against the hostname itself. If you are troubleshooting a particular subdomain, check that exact subdomain instead of assuming every hostname on the same parent domain presents the same certificate.
Next, confirm the port. Port 443 is the standard port for HTTPS and is correct for most websites. Some administration panels, staging systems, APIs, mail services, or other TLS-enabled applications listen on different ports. If your service intentionally uses a custom TLS port, enter it before running the check. The port matters because two services on the same hostname can present different certificates.
Select Check Certificate to perform the lookup. The browser sends the hostname and port to the remote certificate-checking service, which opens the TLS connection and returns the certificate information to this page. This external step is necessary because standard browser JavaScript is restricted from opening arbitrary raw TLS sockets or directly reading another server’s certificate chain. If a lookup fails, confirm that the hostname is public, spelled correctly, resolves in DNS, and accepts TLS connections on the selected port. Use the DNS and Network Troubleshooting guide when the hostname itself will not resolve, and the TCP vs UDP Ports guide when the question is whether you are testing the correct transport and port.
Read the overall certificate status first
The status banner provides the quickest interpretation. A valid, authorized certificate with comfortable time remaining is shown as healthy. A certificate approaching expiration is shown as a warning, while an expired or unauthorized result is shown as a problem that needs attention. Renewal systems are often automated, but automation can fail because of DNS changes, ACME challenge errors, permission problems, an outdated load balancer certificate, or a service that was not reloaded after renewal.
Review expiration and validity dates
The Days Remaining card shows how much time is left before expiration, while the valid-from and valid-to fields show the certificate’s full validity window. If you recently renewed a certificate, use the valid-to date to confirm that the new certificate is actually being served. A renewed file sitting on the server does not help visitors if the web server, reverse proxy, CDN, or load balancer is still presenting the previous certificate.
Check the issuer, subject, and hostname coverage
The issuer identifies the certificate authority that signed the certificate, while the subject or common name provides a concise identity field. For modern hostname validation, pay close attention to the Subject Alternative Name list. SAN entries identify the hostnames the certificate is designed to cover. A certificate may include one hostname, several names, or a wildcard such as *.example.com. If the hostname you are testing is missing from the allowed names, users can receive a name-mismatch warning even when the certificate is current and signed by a trusted authority.
Understand trust and authorization
A certificate can be unexpired and still fail validation. The authorization result helps identify whether the live TLS connection was considered trusted by the checking service. Trust normally depends on a valid chain from the site certificate through the required intermediate certificate authorities to a trusted root. A missing intermediate, self-signed certificate, unknown certificate authority, invalid hostname, or another verification problem can cause failure. An independent check is useful when one device works while another reports a certificate warning.
Review the TLS protocol and cipher
The protocol and cipher fields show what the checker negotiated during its connection. These values confirm that TLS is working and provide a quick technical snapshot of the session. They are not a complete cipher-suite or protocol audit because a server can support many combinations even though one connection negotiates only one. For deeper testing, use a dedicated TLS scanner that enumerates supported protocol versions, cipher suites, and related server settings.
Choose the Next Troubleshooting Layer
An SSL/TLS certificate check is most useful after the hostname resolves and the target port can be reached. If the failure occurs earlier, move down the stack instead of replacing a certificate that may be working correctly.
Check Methodology, Interpretation, and Important Limits
This page does not read a remote server certificate directly from browser JavaScript. Instead, it normalizes the hostname, validates the public host and TCP port, then sends that target to the configured certificate-checking API. The remote service performs the TLS connection and returns the certificate and negotiated-session data displayed here.
Worked example: why an unexpired certificate can still be a problem
Certificate valid-to date: 90 days away
Expired: No
Authorized: No
Interpretation:
The certificate is not expired,
but the remote TLS check did not validate it as authorized/trusted.
Possible causes can include:
• hostname mismatch
• missing intermediate certificate
• untrusted/self-signed issuer
• another certificate-chain validation problem
“Authorized” is the checking service's validation result
The trust/authorization field reflects what the remote checking service reported for its connection. It is not a universal statement about every browser, device, operating system, enterprise trust store, or private certificate authority. A certificate trusted on one managed device can still be untrusted by the public checker, and the reverse can also occur in unusual local environments.
One TLS handshake does not enumerate the server's full configuration
The protocol and cipher fields describe the single connection negotiated by the remote checker. A server may support several TLS versions and many cipher suites even though one connection reports only one protocol and one cipher. Use a dedicated TLS scanner when you need full protocol and cipher-suite enumeration.
SAN display is coverage data, not an independent hostname-verification engine
The page displays Subject Alternative Names returned by the lookup service, but it does not independently reimplement wildcard matching or RFC service-identity verification in browser code. The remote service's authorization result remains the primary validation signal shown by this tool.
Days remaining is approximate
The tool displays the days-until-expiry value returned by the remote service. The exact boundary can differ slightly depending on the service clock, certificate expiration timestamp, time zone presentation, and whether the API rounds or truncates partial days.
Public endpoint only
The hostname validator intentionally rejects localhost and ordinary single-label internal hostnames. The configured API is intended for public endpoints. Private networks, internal DNS zones, VPN-only services, split-horizon names, and certificates reachable only from your own environment are outside this tool's scope.
CDNs, load balancers, and multi-node services can vary
A public hostname may resolve to different edges or backend paths depending on geography, DNS response, load balancing, SNI routing, or deployment state. This check shows what the remote service observed on that request. It does not prove that every node behind the hostname is serving the same certificate.
Rate limits and service failures are not certificate verdicts
The checker can report API rate limits, HTTP errors, timeouts, and network failures. Those conditions mean the lookup could not be completed reliably; they should not be interpreted as proof that the target certificate is invalid.
Related Utiliverse Tools & Guides
Last reviewed: October 9, 2026 · Host normalization, port validation, external lookup behavior, authorization/expiration interpretation, SAN display, TLS protocol/cipher reporting, copy fallback, rate-limit handling, and theme behavior reviewed against the current implementation.
Practical Use Cases for a Domain Certificate Checker
Confirm that a certificate renewal reached production
One of the most useful checks is immediately after renewal. Whether the certificate was renewed manually through a hosting provider or automatically through an ACME client such as Certbot, the new certificate still has to be deployed to the service that users actually reach. In environments with a CDN, reverse proxy, load balancer, multiple web servers, or regional endpoints, renewal and deployment are not always the same event. Checking the live hostname verifies the expiration date that an outside client currently sees.
Troubleshoot browser privacy and trust warnings
When a visitor reports “Your connection is not private,” “certificate not trusted,” or a similar warning, checking the affected hostname can quickly narrow the cause. An expired certificate points toward renewal. An authorization failure can suggest a chain or trust issue. A hostname absent from the SAN list suggests that the wrong certificate may have been installed, or traffic may be reaching an unexpected virtual host. Comparing the apex domain, the www hostname, and application subdomains can reveal whether only one endpoint is misconfigured.
Validate a new website, migration, CDN, or load balancer
Infrastructure changes often move TLS termination from one system to another. A site migration may shift HTTPS from a shared hosting server to a reverse proxy, cloud load balancer, CDN edge, or managed application platform. After DNS is changed, check the public hostname to confirm the new endpoint presents the expected certificate and correct hostname coverage. This is especially useful during staged migrations where the origin server and public edge can have different certificates.
Check multiple subdomains independently
Organizations often run separate certificates or TLS endpoints for www, APIs, login pages, webmail, dashboards, development environments, and customer portals. Even when one wildcard or multi-domain certificate is intended to cover several services, each public endpoint should be checked independently because the certificate actually served depends on the listener and routing configuration. A single outdated node behind a load balancer can also create intermittent problems.
Plan certificate-expiration monitoring
This tool is designed for on-demand checks rather than continuous monitoring, but the remaining-days result can help you decide which systems need automated alerts. Production certificates should normally be renewed well before expiration so there is time to correct failed validation, deployment, or service-reload steps. Teams that manage many domains often monitor certificate expiry alongside uptime and DNS health. Manual spot checks remain useful after maintenance because they confirm what is being served at that moment.
Verify certificates on non-standard TLS ports
HTTPS websites typically use 443, but TLS is also used by many other services and management interfaces. If a service exposes TLS on a custom public port, checking that exact port can reveal a certificate different from the one served on 443. This is helpful when a platform contains several listeners or when a reverse proxy handles the main website while another service terminates TLS itself. Only test systems you are authorized to administer or ordinary public services where connection testing is appropriate.
Use certificate information as one layer of a broader health check
A healthy certificate is important, but it does not prove that a website is fully secure or operational. A valid certificate can exist on a server with an application error, outdated software, weak authentication, unsafe cookies, missing security headers, vulnerable dependencies, or incorrect DNS. For dependable operations, combine live certificate checks with uptime monitoring, DNS validation, security-header review, application testing, backups, patch management, and a dedicated TLS configuration scan when deeper protocol analysis is needed.
SSL Certificate Checker FAQ
What does an SSL certificate checker do?
An SSL certificate checker connects to a public TLS-enabled hostname and reports information about the certificate presented by that service, such as its validity period, issuer, subject, hostname coverage and trust status.
What port should I use for an HTTPS website?
Port 443 is the standard port for HTTPS and is the correct choice for most public websites. Use another port only when the TLS-enabled service is intentionally configured on a custom port.
What does “days remaining” mean?
It is the approximate amount of time between the current check and the certificate’s expiration time. A low value is a signal to verify that renewal and deployment are working before the certificate expires.
What are Subject Alternative Names (SANs)?
SANs are the DNS hostnames a certificate is valid for. Modern browsers primarily use these names when determining whether a certificate matches the hostname a visitor requested.
Why can a certificate be untrusted even when it has not expired?
Expiration is only one part of validation. Trust can also fail because of a missing intermediate certificate, an untrusted issuer, a hostname mismatch, a self-signed certificate, or another verification error.
Can this confirm that an automatic renewal was deployed?
Yes. Checking the live public hostname after renewal is a useful way to confirm that visitors are actually receiving the new certificate rather than an older certificate that remains loaded on a web server, proxy, CDN, or load balancer.
Does this tool upload a private key or certificate file?
No. The tool does not request private keys or local certificate files. The hostname and port you enter are sent to the remote lookup service so it can connect to that public endpoint and return certificate details.
Is a valid SSL certificate the same as a full security audit?
No. Certificate validity is only one part of web security. A complete review can also include TLS versions and cipher suites, security headers, DNS, application vulnerabilities, software patching, authentication, cookies, revocation behavior and server configuration.
Does the TLS protocol shown mean that is the only protocol the server supports?
No. It is the protocol negotiated by the remote checker for that connection. A server can support additional TLS versions and cipher suites that are not enumerated here.
Can different users see a different certificate for the same hostname?
Yes. CDNs, load balancers, geographic routing, SNI configuration, or inconsistent deployments can cause different endpoints to present different certificates.
Does “Authorized” mean every browser will trust the certificate?
No. It is the validation result reported by the remote checking service. Local enterprise trust stores, private certificate authorities, or platform differences can produce different results elsewhere.
Can this check private or internal hostnames?
No. The page is designed for public endpoints and intentionally rejects localhost and ordinary single-label internal names. Do not submit confidential infrastructure names to the external lookup service.
Does an API timeout or rate-limit response mean the certificate is bad?
No. A service or network failure means the lookup was inconclusive. Retry later or verify the endpoint with another trusted certificate or TLS diagnostic tool.