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To download a website’s public SSL certificate, use Firefox to inspect the certificate visually or OpenSSL to retrieve the certificates presented by the server and save a PEM block. The file contains public identity and key information; it does not contain the server’s private key.
“SSL certificate” is the common term, but modern HTTPS uses TLS. Firefox Help describes TLS server certificates as verifying “the ownership and the integrity of the information of websites you visit.”
What you are downloading
An HTTPS server presents a TLS certificate during the connection. The certificate identifies names the server is allowed to represent, contains a public key, and is signed by an issuing certificate authority (CA). It is safe to inspect or share the public certificate.
The private key is kept by the website operator. A browser download or an OpenSSL connection cannot reveal it. Do not ask a site owner for a private key when you only need the public certificate.
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A server may present a leaf (server) certificate and one or more intermediate certificates. The server does not necessarily send every certificate that could appear in a complete trust chain; your browser or operating system may supply trusted roots locally.
Method 1: View the certificate in Firefox
Mozilla documents this Firefox flow in its Secure website certificate help article. Button names and placement can change between Firefox versions, so treat this as the documented Firefox route rather than a universal browser procedure.
- Open the target HTTPS address in Firefox.
- Click the site-information icon beside the address bar.
- Open the secure-connection details and choose More information.
- In the Page Info window, select View Certificate.
- Inspect the certificate page. Firefox can show the server certificate and the intermediate and root certificates in the chain.
Look for the certificate’s subject, Subject Alternative Name (SAN), issuer, validity dates, public-key details, fingerprints, and chain. Firefox describes fingerprints as hashes of the certificate in DER binary form.
The Firefox article explains how to view the certificate. It does not establish that every Firefox release, operating system, or browser offers the same export-file button. If your goal is a file for another program, use OpenSSL or the export controls actually present in your installed version, then verify the resulting file.
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OpenSSL’s s_client is repeatable and script-friendly. The OpenSSL 3.0 manual documents -connect for the host and port, -servername for Server Name Indication (SNI), and -showcerts to display certificates sent by the server.
Run a basic connection
openssl s_client -connect example.com:443 -servername example.com -showcertsReplace both instances of example.com with the hostname you need. Keep the host and SNI name aligned: a shared IP address can serve different certificates for different hostnames.
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The command prints connection diagnostics followed by one or more PEM blocks. A PEM certificate starts with -----BEGIN CERTIFICATE----- and ends with -----END CERTIFICATE-----. Copy the block for the leaf/server certificate into a text file such as example-com.pem. If you need the chain, retain the additional PEM blocks in the order displayed and record which one is the leaf versus an intermediate.
Save the displayed chain on a Unix-like shell
This command writes the PEM blocks from the server response to a file while suppressing most connection diagnostics:
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What the flags do
-connect example.com:443opens a TLS connection to port 443 on the named host.-servername example.comsends SNI, allowing a virtual-hosted server to return the certificate for that hostname.-showcertsdisplays certificates the server sends, not every certificate that might exist in a CA’s possible chain.
For the option definitions and version-specific behavior, see the OpenSSL s_client manual.
Validate the certificate before relying on it
A successful connection or saved file only proves that you obtained certificate data. Check these items for the hostname and environment where the certificate will be used:
- Subject Alternative Name: confirm that the intended DNS name appears in the SAN extension. The common name alone is not enough for modern hostname matching.
- Validity period: check that the current date falls between the certificate’s “not before” and “not after” values, and note any planned renewal deadline.
- Issuer and chain: identify the issuing CA and intermediates. Confirm that the chain leads to a root trusted by the validating operating system or application.
- Correct virtual host: connect using the real hostname and SNI. Connecting only to an IP address can return a different site’s certificate.
- File contents: make sure the file contains certificate delimiters, not a private-key block such as
-----BEGIN PRIVATE KEY-----.
Firefox performs site-name and signature checks through a chain to a trusted CA. Those checks can differ from another operating system, container, Java runtime, or embedded device, so validate in the environment that will actually consume the certificate.
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Or skip the browser setup
ScreenshotNeo is a website screenshot API, not a certificate extractor. It cannot replace Firefox or OpenSSL when you need certificate bytes. It is useful when you need a visual record of a page—such as documenting what a browser showed after you inspect a certificate—without maintaining browser automation. Before capture it accepts cookie or consent banners and removes more than 60 known consent platforms, newsletter popups, and chat widgets; bot checks, blank pages, timeouts, failed loads, and cache hits are not billed. Its MCP server lets Claude, Cursor, or another MCP client call take_screenshot, get_page_info, and capture_pdf.
Use the API documentation at https://screenshotneo.com/docs/ for authentication and all options. A one-call image request is:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://example.com -o shot.webpThe same request in Python:
import requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://example.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)And in Node.js:
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://example.com' });
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Firefox or OpenSSL?
| Need | Firefox | OpenSSL |
|---|---|---|
| Quick visual inspection | Best fit; the certificate and chain are presented in a graphical page. | Terminal output requires interpreting PEM and diagnostic text. |
| Repeatable checks across many hosts | Manual and version-dependent. | Easy to rerun or place in a script with s_client options. |
| Save a PEM file | Export controls vary by Firefox version and platform; the documented page guarantees viewing. | Copy or extract the PEM blocks shown by -showcerts. |
| See certificates sent by the server | Shows the chain as Firefox builds and displays it. | -showcerts displays certificates in the server response; a complete possible chain is not guaranteed. |
| Best for | Readers who want fields, fingerprints, and trust information explained visually. | Developers, operators, and automation that need host/SNI control. |
Troubleshooting
OpenSSL reports a verification or handshake error
First confirm DNS, port 443, and outbound firewall access. Then retry with the exact hostname in both -connect and -servername. A server can require SNI or use a nonstandard TLS configuration. The error may prevent a reliable certificate capture; do not treat a partial output as a valid result.
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This usually means the connection used an IP address, omitted SNI, or targeted a load balancer with several virtual hosts. Use the public hostname and -servername, then verify the SAN before saving the file.
The output contains several certificates
That is normal when the server sends a leaf and intermediates. Identify the leaf by its SAN and subject, preserve intermediates when the consuming application requests a chain, and remember that a root may be supplied by the local trust store rather than sent by the server.
The application rejects the file
Check the required encoding. PEM is text with certificate delimiters; DER is binary. A program that expects DER will reject a PEM file, and the reverse is also true. Confirm whether it wants only the leaf, a concatenated chain, or a CA bundle.
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Firefox shows a warning or an unfamiliar issuer
Read the hostname, dates, issuer, and chain details instead of exporting blindly. A warning can indicate an expired certificate, a name mismatch, an untrusted issuer, or an interception device. If the site is not yours, contact its operator rather than trying to replace trust settings.
The saved file contains no PEM block
Connection diagnostics can obscure the response, or the handshake may have failed. Run the command without redirection, look for the BEGIN CERTIFICATE delimiter, and correct the host, port, and SNI value before trying again.
Certificate tasks that are different
- Importing a certificate: installs trust or identity material into a browser, operating system, server, or application; it is not downloading the server’s current certificate.
- Obtaining a CA certificate: retrieves a root or intermediate from the authority or a trust store, not necessarily the certificate currently presented by a website.
- Exporting a client certificate and private key: moves credentials held locally and requires explicit authorization. It is unrelated to reading a public server certificate.
Frequently Asked Questions
Can I use a downloaded certificate to impersonate the website?
No. The downloaded certificate contains public information. Authentication also requires the server’s private key, which is not exposed by Firefox or an OpenSSL connection.
Why does the certificate fingerprint differ between tools?
Compare the exact certificate being hashed. A server response can contain a leaf plus intermediates, and different tools may display or hash different certificates in that chain.
Should I save the leaf certificate or the entire chain?
Follow the consuming application’s requirement. Some clients need only the leaf; others require the leaf followed by intermediates. A trusted root is often already installed locally and may not be part of the server response.
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