The Caddyfile has a way for you to specify options that apply globally. Some options act as default values, while others customize the behavior of the Caddyfile [adapter](/docs/config-adapters).
The very top of your Caddyfile can be a **global options block**. This is a block that has no keys:
Configures Caddy's storage mechanism. The default is [`file_system`](/docs/json/storage/file_system/). There are many other available [storage modules](/docs/json/storage/) provided as plugins.
How often to scan storage units for old or expired assets and remove them. These scans exert lots of reads (and list operations) on the storage module, so choose a longer interval for large deployments. The value is a [duration value](/docs/conventions#durations). Default: 24h.
Storage will always be cleaned when the process first starts. Then, a new cleaning will be started this duration after the previous cleaning started if the previous cleaning finished in less than half the time of this interval (otherwise next start will be skipped).
Customizes the [admin API endpoint](/docs/api). If `off`, then the admin endpoint will be disabled. If disabled, config changes will be impossible without stopping and starting the server.
- **origins** configures the list of remotes/origins that are allowed to connect to the endpoint.
- **enforce_origin** enables enforcement of the Origin header. (This is different from enforcing origins generally, which is always done.)
Customizes the named logger. The name can be passed to indicate a specific logger to customize the behavior for. If no name is specified, the behavior of the default logger is modified. This option can be specified multiple times to configure different loggers. You can read more about the default logger and other logging behaviors in the [logging documentation](/docs/logging/).
- **output** configures where to write the logs. See the [log directive](/docs/caddyfile/directives/log#output-modules) documentation for more information, which has the same structure.
- **format** describes how to encode, or format, the logs. See the [log directive](/docs/caddyfile/directives/log#format-modules) documentation for more information, which has the same structure.
- **level** is the minimum entry level to log. Default: `INFO`
- **include** identifies the loggers that are included in this log configuration. See the [JSON documentation](/docs/json/logging/logs/include/) for more information.
- **exclude** identifies the loggers that are excluded from this log configuration. See the [JSON documentation](/docs/json/logging/logs/exclude/) for more information.
Defines the grace period for shutting down HTTP servers during config reloads. If clients do not finish their requests within the grace period, the server will be forcefully terminated to allow the reload to complete and free up resources.
Configure automatic HTTPS. It can be disabled entirely (`off`), disable only HTTP-to-HTTPS redirects (`disable_redirects`), or be configured to automate certificates even for names which appear on manually-loaded certificates (`ignore_loaded_certs`). See the [Automatic HTTPS](/docs/automatic-https) page for more details.
Your email address. Mainly used when creating an ACME account with your CA, and is highly recommended in case there are problems with your certificates.
##### `default_sni`
Sets a default TLS ServerName for when clients do not use SNI in their ClientHello.
##### `local_certs`
Causes all certificates to be issued internally by default, rather than through a (public) ACME CA such as Let's Encrypt. This is useful in development environments.
Specifies the URL to the ACME CA's directory. It is strongly recommended to set this to Let's Encrypt's [staging endpoint](https://letsencrypt.org/docs/staging-environment/) for testing or development. Default: ZeroSSL and Let's Encrypt's production endpoints.
Configures the ACME DNS challenge provider to use for all ACME transactions. The tokens following the name of the provider set up the provider the same as if specified in the [`tls` directive's `acme` issuer](/docs/caddyfile/directives/tls#acme).
Configures [On-Demand TLS](/docs/automatic-https#on-demand-tls) where it is enabled, but does not enable it (to enable it, use the [on_demand `tls` subdirective](/docs/caddyfile/directives/tls#syntax)). Highly recommended if using in production environments, to prevent abuse.
- **ask** will cause Caddy to make an HTTP request to the given URL with a query string of `?domain=` containing the value of the domain name. If the endpoint returns 200 OK, Caddy will be authorized to obtain a certificate for that name.
Defines the issuer (or source) of TLS certificates. The tokens following the name of the issuer set up the issuer the same as if specified in the [`tls` directive](/docs/caddyfile/directives/tls#issuer). May be repeated if you wish to configure more than one issuer to try. They will be tried in the order they are defined.
##### `ocsp_stapling`
Can be set to `off` to disable OCSP stapling. Useful in environments where responders are not reachable due to firewalls.
If your CA provides multiple certificate chains, you can use this option to specify which chain Caddy should prefer. Set one of the following options:
- **smallest** will tell Caddy to prefer chains with the fewest amount of bytes.
- **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** 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.
Note! Specifying `preferred_chains` as a global option will affect all issuers if there isn't any [overriding issuer level config](/docs/caddyfile/directives/tls#acme).
Customizes [HTTP servers](/docs/json/apps/http/servers/) with settings that potentially span multiple sites and thus can't be rightly configured in site blocks. These options affect the listener/socket, or other behavior beneath the HTTP layer.
Can be specified more than once, with different `listener_address` values, to configure different options per server. For example, `servers :443` will only apply to the server that is bound to the listener address `:443`. Omitting the listener address will apply the options to any remaining server.
<asideclass="tip">
Use the <ahref="/docs/command-line#caddy-adapt"><code>caddy adapt</code></a> command to find the listen address for the servers in your Caddyfile.
</aside>
For example, to configure different options for the servers on port `:80` and `:443`, you would specify two `servers` blocks:
```caddy
{
servers :443 {
protocol {
experimental_http3
}
}
servers :80 {
protocol {
allow_h2c
}
}
}
```
##### `listener_wrappers`
Allows configuring [listener wrappers](/docs/json/apps/http/servers/listener_wrappers/), which can modify the behaviour of the base listener. They are applied in the given order.
There is a special no-op [`tls`](/docs/json/apps/http/servers/listener_wrappers/tls/) listener wrapper provided as a standard module which marks where TLS should be handled in the chain of listener wrappers. It should only be used if another listener wrapper must be placed in front of the TLS handshake.
For example, assuming you have the [`proxy_protocol`](/docs/json/apps/http/servers/listener_wrappers/proxy_protocol/) plugin installed:
- **read_body** is a [duration value](/docs/conventions#durations) that sets how long to allow a read from a client's upload. Setting this to a short, non-zero value can mitigate slowloris attacks, but may also affect legitimately slow clients. Defaults to no timeout.
- **read_header** is a [duration value](/docs/conventions#durations) that sets how long to allow a read from a client's request headers. Defaults to no timeout.
- **write** is a [duration value](/docs/conventions#durations) that sets how long to allow a write to a client. Note that setting this to a small value when serving large files may negatively affect legitimately slow clients. Defaults to no timeout.
- **idle** is a [duration value](/docs/conventions#durations) that sets the maximum time to wait for the next request when keep-alives are enabled. Defaults to 5 minutes to help avoid resource exhaustion.
The maximum size to parse from a client's HTTP request headers. It accepts all formats supported by [go-humanize](https://github.com/dustin/go-humanize/blob/master/bytes.go).
##### `protocol`
- **allow_h2c** enables H2C ("Cleartext HTTP/2" or "H2 over TCP") support, which will serve HTTP/2 over plaintext TCP connections if a client support it. Because this is not implemented by the Go standard library, using H2C is incompatible with most of the other options for this server. Do not enable this only to achieve maximum client compatibility. In practice, very few clients implement H2C, and even fewer require it. This setting applies only to unencrypted HTTP listeners. ⚠️ Experimental feature; subject to change or removal.
- **experimental_http3** enables experimental draft HTTP/3 support. Note that HTTP/3 is not a finished spec and client support is extremely limited. This option will go away in the future. _This option is not subject to compatibility promises._
- **strict_sni_host** require that a request's `Host` header matches the value of the ServerName sent by the client's TLS ClientHello; often a necessary safeguard when using TLS client authentication.
