**Caddy's default TLS settings are secure. Only change these settings if you have a good reason and understand the implications.** The most common use of this directive will be to specify an ACME account email address, change the ACME CA endpoint, or to provide your own certificates.
Compatibility note: Due to its sensitive nature as a security protocol, deliberate adjustments to TLS defaults may be made in new minor or patch releases. Old or broken TLS versions, ciphers, features, etc. may be removed at any time. If your deployment is extremely sensitive to changes, you should explicitly specify those values which must remain constant, and be vigilant about upgrades. In almost every case, we recommend using the default settings.
- **internal** means to use Caddy's internal, locally-trusted CA to produce certificates for this site. To further configure the [`internal`](#internal) issuer, use the [`issuer`](#issuer) subdirective.
- **<email>** is the email address to use for the ACME account managing the site's certificates. You may prefer to use the [`email` global option](/docs/caddyfile/options#email) instead, to configure this for all your sites at once.
Keep in mind that Let's Encrypt may send you emails about your certificate nearing expiry, but this may be misleading because Caddy may have chosen to use a different issuer (e.g. ZeroSSL) when renewing. Check your logs and/or the certificate itself (in your browser for example) to see which issuer was used, and that its expiry is still valid; if so, you may safely ignore the email from Let's Encrypt.
- **protocols** <spanid="protocols"/> specifies the minimum and maximum protocol versions. DO NOT change these unless you know what you're doing. Configuring this is rarely necessary, because Caddy will always use modern defaults.
- **ciphers** <spanid="ciphers"/> specifies the list of cipher suite names in descending preference order. DO NOT change these unless you know what you're doing. Note that cipher suites are not customizable for TLS 1.3; and not all TLS 1.2 ciphers are enabled by default. The supported names are (in no particular order here):
- **alpn** <spanid="alpn"/> is the list of values to advertise in the [ALPN extension <img src="/old/resources/images/external-link.svg" class="external-link">](https://developer.mozilla.org/en-US/docs/Glossary/ALPN) of the TLS handshake.
- **ca** <spanid="ca"/> changes the ACME CA endpoint. This is most often used to set [Let's Encrypt's staging endpoint <img src="/old/resources/images/external-link.svg" class="external-link">](https://letsencrypt.org/docs/staging-environment/) when testing, or an internal ACME server. (To change this value for the whole Caddyfile, use the `acme_ca` [global option](/docs/caddyfile/options) instead.)
- **ca_root** <spanid="ca_root"/> specifies a PEM file that contains a trusted root certificate for the ACME CA endpoint, if not in the system trust store.
- **dns** <spanid="dns"/> enables the [DNS challenge](/docs/automatic-https#dns-challenge) using the specified provider plugin, which must be plugged in from one of the [`caddy-dns` <img src="/old/resources/images/external-link.svg" class="external-link">](https://github.com/caddy-dns) repositories. Each provider plugin may have their own syntax following their name; refer to their docs for details. Maintaining support for each DNS provider is a community effort. [Learn how to enable the DNS challenge for your provider at our wiki.](https://caddy.community/t/how-to-use-dns-provider-modules-in-caddy-2/8148)
- **propagation_timeout** <spanid="propagation_timeout"/> is a [duration value](/docs/conventions#durations) that sets the maximum time to wait for the DNS TXT records to appear when using the DNS challenge. Set to `-1` to disable propagation checks. Default 2 minutes.
- **propagation_delay** <spanid="propagation_delay"/> is a [duration value](/docs/conventions#durations) that sets how long to wait before starting DNS TXT records propagation checks when using the DNS challenge. Default `0` (no wait).
- **dns_ttl** <spanid="dns_ttl"/> is a [duration value](/docs/conventions#durations) that sets the TTL of the `TXT` record used for the DNS challenge. Rarely needed.
- **dns_challenge_override_domain** <spanid="dns_challenge_override_domain"/> overrides the domain to use for the DNS challenge. This is to delegate the challenge to a different domain.
You may want to use this if your primary domain's DNS provider does not have a [DNS plugin <img src="/old/resources/images/external-link.svg" class="external-link">](https://github.com/caddy-dns) available. You can instead add a `CNAME` record with subdomain `_acme-challenge` to your primary domain, pointing to a secondary domain for which you _do_ have a plugin.
When ACME issuers try to solve the DNS challenge for your primary domain, they will then follow the `CNAME` to your secondary domain to find the `TXT` record.
- **resolvers** <spanid="resolvers"/> customizes the DNS resolvers used when performing the DNS challenge; these take precedence over system resolvers or any default ones. If set here, the resolvers will propagate to all configured certificate issuers.
This is typically a list of IP addresses. For example, to use [Google Public DNS <img src="/old/resources/images/external-link.svg" class="external-link">](https://developers.google.com/speed/public-dns):
- **on_demand** <spanid="on_demand"/> enables [On-Demand TLS](/docs/automatic-https#on-demand-tls) for the hostnames given in the site block's address(es). **Security warning:** Doing so in production is insecure unless you also configure the [`on_demand_tls` global option](/docs/caddyfile/options#on-demand-tls) to mitigate abuse.
Multiple `trusted_*` directives may be used to specify multiple CA or leaf certificates. Client certificates which are not listed as one of the leaf certificates or signed by any of the specified CAs will be rejected according to the **mode**.
- **issuer** <spanid="issuer"/> configures a custom certificate issuer, or a source from which to obtain certificates.
Which issuer is used and the options that follow in this segment depend on the [issuer modules](#issuers) that are available. Some of the other subdirectives such as `ca` and `dns` are actually shortcuts for configuring the `acme` issuer (and this subdirective was added later), so specifying this directive and some of the others is confusing and thus prohibited.
This subdirective can be specified multiple times to configure multiple, redundant issuers; if one fails to issue a cert, the next one will be tried.
- **insecure_secrets_log** <spanid="insecure_secrets_log"/> enables logging of TLS secrets to a file. This is also known as `SSLKEYLOGFILE`. Uses NSS key log format, which can then be parsed by Wireshark or other tools. ⚠️ **Security Warning:** This is insecure as it allows other programs or tools to decrypt TLS connections, and therefore completely compromises security. However, this capability can be useful for debugging and troubleshooting.
Obtains certificates using the ACME protocol. Note that `acme` is a default issuer (using Let's Encrypt), so configuring it explicitly is usually unnecessary.
- **test_dir** <spanid="test_dir"/> is an optional fallback directory to use when retrying challenges; if all challenges fail, this endpoint will be used during retries; useful if a CA has a staging endpoint where you want to avoid rate limits on their production endpoint.
- **alt_http_port** <spanid="alt_http_port"/> is an alternate port on which to serve the HTTP challenge; it has to happen on port 80 so you must forward packets to this alternate port.
- **alt_tlsalpn_port** <spanid="alt_tlsalpn_port"/> is an alternate port on which to serve the TLS-ALPN challenge; it has to happen on port 443 so you must forward packets to this alternate port.
- **propagation_timeout** <spanid="propagation_timeout"/> is a [duration value](/docs/conventions#durations) that sets the maximum time to wait for the DNS TXT records to appear when using the DNS challenge. Set to `-1` to disable propagation checks. Default 2 minutes.
- **propagation_delay** <spanid="propagation_delay"/> is a [duration value](/docs/conventions#durations) that sets how long to wait before starting DNS TXT records propagation checks when using the DNS challenge. Default 0 (no wait).
- **dns_ttl** <spanid="dns_ttl"/> is a [duration value](/docs/conventions#durations) that sets the TTL of the `TXT` record used for the DNS challenge. Rarely needed.
- **dns_challenge_override_domain** <spanid="dns_challenge_override_domain"/> overrides the domain to use for the DNS challenge. This is to delegate the challenge to a different domain.
You may want to use this if your primary domain's DNS provider does not have a [DNS plugin <img src="/old/resources/images/external-link.svg" class="external-link">](https://github.com/caddy-dns) available. You can instead add a `CNAME` record with subdomain `_acme-challenge` to your primary domain, pointing to a secondary domain for which you _do_ have a plugin.
When ACME issuers try to solve the DNS challenge for your primary domain, they will then follow the `CNAME` to your secondary domain to find the `TXT` record.
- **resolvers** <spanid="resolvers"/> customizes the DNS resolvers used when performing the DNS challenge; these take precedence over system resolvers or any default ones. If set here, the resolvers will propagate to all configured certificate issuers.
This is typically a list of IP addresses. For example, to use [Google Public DNS <img src="/old/resources/images/external-link.svg" class="external-link">](https://developers.google.com/speed/public-dns):
- **preferred_chains** <spanid="preferred_chains"/> specifies which certificate chains Caddy should prefer; useful if your CA provides multiple chains. Use one of the following options:
- **smallest** <spanid="smallest"/> will tell Caddy to prefer chains with the fewest amount of bytes.
- **root_common_name** <spanid="root_common_name"/> is a list of one or more common names; Caddy will choose the first chain that has a root that matches with at least one of the specified common names.
- **any_common_name** <spanid="any_common_name"/> is a list of one or more common names; Caddy will choose the first chain that has an issuer that matches with at least one of the specified common names.
Obtains certificates using the ACME protocol, specifically with ZeroSSL. Note that `zerossl` is a default issuer, so configuring it explicitly is usually unnecessary.
The syntax for `zerossl` is exactly the same as for [`acme`](#acme), except that its name is `zerossl` and it can optionally take your ZeroSSL API key.
Its functionality is also the same, except that it will use ZeroSSL's directory by default and it can automatically negotiate EAB credentials (whereas with the `acme` issuer, you have to manually provide EAB credentials and set the directory endpoint).
- **ca** <spanid="ca"/> is the name of the internal CA to use. Default: `local`. See the [PKI app global options](/docs/caddyfile/options#pki-options) to configure the `local` CA, or to create alternate CAs.
By default, the root CA certificate has a `3600d` lifetime (10 years) and the intermediate has a `7d` lifetime (7 days).
Caddy will attempt to install the root CA certificate to the system trust store, but this may fail when Caddy is running as an unprivileged user, or when running in a Docker container. In that case, the root CA certificate will need to be manually installed, either by using the [`caddy trust`](/docs/command-line#caddy-trust) command, or by [copying out of the container](/docs/running#usage).
- **lifetime** <spanid="lifetime"/> is a [duration value](/docs/conventions#durations) that sets the validity period for interally issued leaf certificates. Default: `12h`. It is NOT recommended to change this, unless absolutely necessary. It must be shorter than the intermediate's lifetime.
- **sign_with_root** <spanid="sign_with_root"/> forces the root to be the issuer instead of the intermediate. This is NOT recommended and should only be used when devices/clients do not properly validate certificate chains (very uncommon).
Certificate manager modules are distinct from issuer modules in that use of manager modules implies that an external tool or service is keeping the certificate renewed, whereas an issuer module implies that Caddy itself is managing the certificate. (Issuer modules take a Certificate Signing Request (CSR) as input, but certificate manager modules take a TLS ClientHello as input.)
These manager modules come standard with the `tls` directive:
Get certificates from a locally-running [Tailscale <img src="/old/resources/images/external-link.svg" class="external-link">](https://tailscale.com) instance. [HTTPS must be enabled in your Tailscale account](https://tailscale.com/kb/1153/enabling-https/) (or your open source [Headscale server <img src="/old/resources/images/external-link.svg" class="external-link">](https://github.com/juanfont/headscale)); and the Caddy process must either be running as root, or you must configure `tailscaled` to give your Caddy user [permission to fetch certificates](https://github.com/caddyserver/caddy/pull/4541#issuecomment-1021568348).
Get certificates by making an HTTP(S) request. The response must have a `200` status code and the body must contain a PEM chain including the full certificate (with intermediates) as well as the private key.
- **url** <spanid="url"/> is the fully-qualified URL to which to make the request. It is strongly advised that this be a local endpoint for performance reasons. The URL will be augmented with the following query string parameters:
-`server_name`: SNI value
-`signature_schemes`: comma-separated list of hex IDs of signature algorithms
-`cipher_suites`: comma-separated list of hex IDS of cipher suites
Use locally-trusted certificates for all hosts on the current site block, rather than public certificates via ACME / Let's Encrypt (useful in dev environments):
Specify an email address for your ACME account (but if only one email is used for all sites, we recommend the `email` [global option](/docs/caddyfile/options) instead):
Enable TLS Client Authentication and require clients to present a valid certificate that is verified against all the provided CA's via `trusted_ca_cert_file`
