Localhost and certificates

Acira opens servers on your own computer and devices on your own network, such as a router, without sending those addresses to a search engine. This page shows how to reach them, what happens when their certificate is not trusted, and how the sign-in prompt for HTTP authentication works.

Open a local address

Click the address bar, or press Ctrl+L (Cmd+L on a Mac).
Type the address, for example localhost:3000 or 192.168.1.1, and press Enter.

When you type an address without http:// or https://, Acira picks the scheme for you:

You type	Acira opens
`localhost`, `localhost:3000`, `app.localhost`	HTTP
An address ending in `.local`, such as `printer.local`	HTTP
An IPv4 address on your own network: `127.x.x.x`, `10.x.x.x`, `192.168.x.x`, `172.16.x.x` to `172.31.x.x`, `169.254.x.x`	HTTP
The IPv6 loopback `[::1]` and private IPv6 addresses (those starting with `fc`, `fd` or `fe80` to `febf`)	HTTP
Any other address with a dot, such as `router.lan` or `example.com`	HTTPS, then HTTP. If the secure connection cannot be made, Acira opens it over HTTP and shows This site has no secure connection, so it opened over http.
An address that starts with `http://` or `https://`	Exactly what you typed. Acira never changes an explicit scheme, even when the HTTPS connection fails certificate checks.

A single word with no dot, such as router, is treated as a search. Type router.lan, or add the scheme.

A page opened over HTTP shows Not secure in the address bar. Addresses that contain a user name or password, like http://admin:secret@192.168.1.1, are refused with Remove the sign-in details from the address. Acira shows a sign-in window instead (see below).

If nothing is running there

Acira shows Nothing is running on followed by the address, and says the connection was refused. Check that the server or device is on and that the port in the address is right, then choose Try again.

Always use HTTPS and local addresses

If you turn on Settings › Privacy › Always use HTTPS (it is off by default), Acira upgrades websites to HTTPS and asks before using HTTP. Local addresses are left alone: loopback and private IP addresses, names with no dot, and names ending in .localhost, .local, .internal, .lan, .home.arpa and .onion. Insecure WebSockets (ws:) to those addresses still work, and to other addresses they are blocked.

For another site that has no HTTPS, Acira asks Allow an HTTP connection? with the buttons Cancel and Allow HTTP in this tab. The exception covers that one site in that tab until you leave it or close the tab.

Local network permission

A public website that wants to reach a device or server on your own network must ask your permission. The prompt reads wants to connect to devices on your local network or wants to connect to apps on this computer. Your choice is saved with the other site permissions in Settings › Privacy › Site permissions. If a public page sends you to a local address without that permission, the error page says The connection is blocked because it was initiated by a public page to connect to devices or servers on your local network. See Site permissions and data.

Certificate warnings

Routers, network drives and development servers often use a certificate that no authority signed. When that happens Acira shows Your connection is not private and says that the server could not prove who it is. The page explains the reason: a certificate no trusted authority signed, one issued for a different address, or one that has expired or is not yet valid. For a local device, it adds that routers and other local devices often use their own certificate.

Continue to a device on your own network

On the warning page, choose Continue to site (unsafe). It is a quiet link below the buttons.
Read the warning. Acira names the host and says the exception applies to this tab and this certificate for 5 minutes.
Choose Proceed to followed by the host (unsafe).

The page loads, and the address bar shows that the identity is not verified. Open the notice to read You allowed this tab to connect without a verified certificate until a time. To end it sooner, choose Remove exception.

What the exception covers

One tab. Other tabs, and other windows, still see the warning.
One certificate. If the server presents a different certificate, you see the warning again.
One site. It covers that host and port in that tab.
5 minutes. When it ends, Acira stops the page and closes its connections to that site. Loading the site again shows the warning. The warning itself also stays valid for a short time. If you wait too long before you proceed, Acira says This warning has expired. Try again to review it.
Nothing is saved. The exception is not written to disk, and a restart ends it.

Which warnings you can continue past

Address	Continue is offered
`https://localhost` and names ending in `.localhost`	Yes, for an untrusted authority, a name mismatch or an expired certificate
A private IP address, such as `https://192.168.1.1` or `https://10.0.0.1`, or a loopback or private IPv6 address	Yes, for the same three errors
A name that resolves through DNS, such as `nas.local`, `router.lan` or `staging.example.com`	No. Acira says that the warning can’t be bypassed and that exceptions are offered for devices on your own network.
Any address, when the certificate is revoked, uses a weak key or signature, breaks name constraints or is pinned	No

HTTP authentication

Some servers, routers and proxies ask for a user name and password before they send a page. Acira shows its own window for this.

When the sign-in window opens, check the line Destination site and the text the site sent after The site says:.
Type your Username and Password.
Choose Sign in, or Cancel to stop.

The window title is Sign in to this site, or Sign in to this proxy when an HTTP proxy asks. For a proxy, the text reads The proxy says:.
The details go to that site or proxy. Acira does not save them.
If the connection is plain HTTP, the window says so: This site uses an unencrypted HTTP connection. The details are sent without encryption.
If the details are refused, the window opens again with The site did not accept the previous details. Try again or cancel. Your user name is kept, and you retype the password.
If you do not answer within 2 minutes, the request is cancelled. When several sites ask at the same time, the window says how many others are waiting.
The user name cannot contain a colon.

Other ways to work locally

Open a file from your computer. Press Ctrl+O (Cmd+O on a Mac), or drag the file into the window. Acira opens pages (.html, .htm, .xhtml), PDFs, pictures, text files (.txt, .md, .csv, .json, .log), sound and video. For any other kind of file it says Acira can’t open this kind of file. Typing a file: address does not work.
Use a separate profile or a private tab for a clean cookie jar. See Profiles and Private tabs and windows.
Inspect the page. See Developer tools.
Build an extension. See Building and testing extensions.

Last updated October 31, 2026