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To use a memorable local hostname such as myapp.test on Windows, add that name to the Windows hosts file and use the identical name as the site address in Caddy. The hosts entry controls where Windows sends the request; Caddy’s site address controls which configuration handles it. Caddy can then serve the site over HTTPS with its local certificate authority. Name resolution and certificate trust are separate steps, so a working hosts entry does not by itself make a browser trust the HTTPS certificate.
What this setup does
Windows checks its local hosts file before asking DNS to resolve a name. A line such as 127.0.0.1 myapp.test therefore tells that computer to send requests for myapp.test to its own loopback address. The entry is local configuration, not a DNS record: another laptop, phone, virtual machine, or colleague’s workstation will not learn the name from your file.
Caddy receives the request after Windows resolves the name. It selects a site by comparing the request’s Host value with the site address in the Caddyfile. Consequently, the browser hostname, hosts-file hostname, and Caddy site address must match exactly. Two names can point to the same IP address and still select different Caddy sites.
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For local and internal names, Caddy uses its own local certificate authority rather than ACME or public DNS validation. The browser can still show a trust warning until the machine—and, depending on the browser, its separate trust store—trusts Caddy’s local root certificate.
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Before you start
- Windows with permission to edit files in
C:WindowsSystem32driversetc. - Caddy installed and available from a terminal.
- A hostname you will use consistently.
myapp.testis only an example; no particular suffix is required. - A local application, static directory, or upstream service that Caddy should serve.
Decide whether the site is static or whether Caddy should proxy to a development server. That choice changes the handler in the Caddyfile, but not the hosts-file mapping.
Choose the hostname and local address
For a service running on the same Windows computer, map the hostname to loopback:
127.0.0.1 myapp.testThe IP address identifies where the service listens; the hostname is the name you will type in the browser. You may add a comment with # to document the purpose:
127.0.0.1 myapp.test # local development siteDo not assume that a hosts-file entry creates a domain that is reachable from the internet. It affects only the computer containing the entry. If other devices must resolve the same name, configure suitable network DNS for those clients instead of copying a single-machine workaround.
Edit the Windows hosts file as administrator
Find the file
Windows stores the file at:
C:WindowsSystem32driversetchostsThe filename is exactly hosts; it has no .txt extension. Because the file is in a protected system directory, a normal editor window may be unable to save changes.
Use an elevated text editor
- Open your text editor with Run as administrator. If Windows asks for consent, approve it.
- In the editor’s Open dialog, browse to
C:WindowsSystem32driversetc. - Change the file filter from text documents to all files if
hostsis not visible. - Open
hosts, add the mapping on its own line, and save without adding an extension.
Microsoft’s PowerToys Hosts File Editor is an optional graphical alternative. Its administrator mode is designed for editing this protected file. Any editor is acceptable if it actually writes the file with elevated rights.
Check the line you added
Keep the address and hostname separated by whitespace. Avoid introducing a typo, trailing extension, or a second hostname that you do not intend to use. The name you type later must be the same sequence of characters shown here.
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Write a matching Caddyfile
Create a file named Caddyfile in a convenient development directory. The first line is the site address, and the directives inside the braces define how Caddy responds.
Quick response for a routing check
Use a response handler to prove that hostname matching works before involving an application:
myapp.test {
respond "Caddy is serving myapp.test"
}This test distinguishes a Caddy routing problem from an application problem. Once it responds correctly, replace respond with the handler your project needs.
Serve static files
For a directory of HTML, CSS, JavaScript, or other assets, use a root and file server:
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myapp.test {
root * C:/dev/myapp
file_server
}Use forward slashes in the Windows path to keep the Caddyfile easy to read. Replace the example directory with the actual project location.
Proxy to a development server
If another process listens on a local port, pass requests through with reverse_proxy:
myapp.test {
reverse_proxy 127.0.0.1:3000
}The upstream application can continue listening on its usual port while browsers use the custom hostname and Caddy’s HTTPS endpoint.
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Start Caddy and open the site
- Open a terminal in the directory containing the Caddyfile.
- Start Caddy with that configuration:
caddy run --config CaddyfileCaddy serves local sites over HTTPS by default. On first use it may ask for your password because installing its local root certificate requires elevated permission.
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- In the browser, visit the exact hostname, for example
https://myapp.test. - If you change the Caddyfile while Caddy is running, apply the change with:
caddy reload --config CaddyfileWhen you are finished, stop the running Caddy process with:
caddy stopUse the same Caddyfile path for reloads that you used to start the process so the intended configuration is replaced.
Make Caddy’s local HTTPS certificate trusted
Correct name resolution and certificate trust are independent. The hosts file can send myapp.test to 127.0.0.1 while the browser still warns that the certificate issuer is unknown.
Automatic installation
When Caddy starts local HTTPS for the first time, it may offer to install its local root certificate and request administrator approval. Accepting that prompt installs trust for the Windows environment where Caddy is running.
Install the root certificate on Windows
Caddy keeps its application data under %AppData%Caddy. Its local root certificate is stored beneath the local authority directory. From an elevated Command Prompt, Caddy documents installing that certificate with Windows certutil:
certutil -addstore -f "ROOT" "%AppData%Caddypkiauthoritieslocalroot.crt"Run the command with the same Windows account and Caddy data directory that created the certificate. If the certificate is installed for one account but Caddy is running under another, the stores may not contain the same root.
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Account for browser-specific stores
Some browsers maintain a trust store separate from the Windows certificate store. If Windows trusts the root but a browser continues to warn, follow that browser’s certificate-import procedure and add Caddy’s local root there as well. A trust warning at this stage does not prove that the hosts mapping is wrong.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Hosts file versus DNS: which approach fits?
| Consideration | Windows hosts file with Caddy | DNS with Caddy’s public HTTPS workflow |
|---|---|---|
| Where the name is resolved | Only on the Windows computer containing the entry | By DNS for clients that can reach the configured DNS service |
| Public domain registration | Not required for a local mapping | Uses a registered public domain |
| Internet reachability | Local-machine scope | Requires external access to ports 80 and 443 for the public setup |
| Certificate model | Caddy local certificate authority; clients must trust its root | Public certificate issuance through Caddy’s automatic HTTPS flow |
| Best use | One developer’s local site or an isolated internal test | A service intended for clients outside the local computer |
The hosts-file method is useful precisely because it avoids changing public DNS. It is not a substitute for network DNS when several devices need the same name, and it does not publish a service to the internet.
Troubleshoot the common failure modes
The browser shows the wrong site or a default response
Compare the hostname in the address bar character by character with the hosts-file line and the Caddy site address. Caddy matches named sites using the request’s Host header. A request for www.myapp.test, for example, is not the same as a site configured only for myapp.test. Correct the names, then reload the Caddyfile.
The name resolves, but HTTPS is blocked or warns
First separate the two questions: did Windows resolve the hostname to the intended address, and does the browser trust the certificate? If the first is correct, install Caddy’s local root certificate in the Windows store and, where necessary, the browser’s separate store. Caddy’s local HTTPS does not use public ACME validation for internal names.
Windows will not save the hosts file
Close the editor, reopen it with administrator rights, and open the extensionless file from the system directory again. PowerToys Hosts File Editor can provide an administrator-mode interface. Saving a file named hosts.txt does not modify the hosts file Windows reads.
Changes to the Caddyfile do not appear
Reload the running configuration:
caddy reload --config CaddyfileConfirm that the command targets the same file used when Caddy was started. A syntax or configuration error will prevent the new configuration from taking effect; read the terminal output and correct the indicated directive.
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That behavior is expected when only one Windows hosts file was edited. The mapping is not distributed to other clients. Provide an appropriate DNS service for the network, or create equivalent local mappings on each client if that limited arrangement is acceptable.
A repeatable checklist
- Pick one hostname and keep its spelling identical everywhere.
- Add
127.0.0.1 hostnameto the elevated Windows hosts file. - Use the same hostname as the Caddyfile site address.
- Select one handler:
respondfor a test,file_serverfor static content, orreverse_proxyfor an application server. - Start Caddy from the directory containing the Caddyfile.
- Open
https://hostname, not a different alias. - Trust Caddy’s local root certificate in Windows and, if needed, in the browser.
- Reload Caddy after configuration edits and stop it when the development session ends.
This arrangement gives one Windows machine a convenient custom name and Caddy-managed local HTTPS without registering a public domain. Its deliberate boundary is scope: hosts-file resolution stays on that computer, while shared or public access requires DNS and an appropriately exposed Caddy deployment.
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