Localhost:18789 Not Working? Easy Fixes That Actually Work

If you typed http://localhost:18789 into your browser and got a “can’t reach this site” page, here is the short version: your browser did exactly what it was supposed to do, but nothing answered on your own computer at port 18789. That address does not point to a website on the internet. It points back to your own machine, and port 18789 is just a numbered door that some program on your machine is supposed to be listening behind. When the door is closed — because the program is not running, it started on a different port, or a firewall got in the way — the browser has nothing to show you.

That sounds frustrating, but it is actually good news. A localhost problem is a local problem, which means you can usually fix it yourself in a few minutes without waiting on anyone else, changing any internet settings, or reinstalling anything. Most of the time the fix is one of three things: start the service again, use the port it actually started on, or clear out a stale browser tab or cached redirect that is sending you to the wrong place. The rest of this guide works through those checks in the order that solves the problem fastest, and explains what each piece means along the way so you are not just copying commands blindly.

In this article:

• What localhost:18789 actually means
• Why your browser says it cannot reach this site
• The five-minute checklist that fixes most cases
• How to tell whether anything is listening on port 18789
• What to do when the port is already in use
• Firewall, antivirus, and browser problems that block localhost
• How to change the port safely
• When localhost:18789 is supposed to be something else
• Frequently asked questions

What localhost:18789 Actually Means

Break the address into two parts and it stops looking mysterious. “Localhost” is a name your computer gives to itself. Whenever software on your machine talks to localhost, it is talking to that same machine, not to a server somewhere else. Under the hood, localhost normally resolves to the loopback address 127.0.0.1, which is a special address that never leaves your computer. Network traffic sent to 127.0.0.1 loops straight back to the machine that sent it. That is why developers use it for testing: you can run a website, an app, or a tool on your own computer and open it in your browser without putting anything on the public internet.

Key: localhost. A hostname that refers to your own computer, normally resolving to 127.0.0.1.

Key: loopback address. The 127.0.0.1 address range, used for traffic that stays inside one machine.

Key: port. A number from 1 to 65535 that tells your computer which program should receive the traffic. A port is like an apartment number on top of the building address.

The second part, 18789, is the port number. Think of your computer’s address as a building and each port as a different door. A web server might listen at door 80 or 443, a development server might use 3000, 5000, or 8000, and some other tool might pick 18789. There is nothing special about 18789 itself. It is not a standard web port, and it is not reserved for any one famous program. It is simply a high-numbered port that a particular application, service, or development tool happened to choose, either because its maker picked it as a default or because a user configured it that way. That is an important clue: if you are trying to open localhost:18789, you probably have — or recently had — a specific program in mind that was supposed to be serving something there. A game server, a local dashboard, a media tool, a development project, a proxy, or a background service could all sit behind that port. The browser does not know or care which one. It just knocks on door 18789 and waits for an answer.

That also explains why searching the web for “localhost:18789” rarely gives you a single clean answer. Two people can both use port 18789 for completely different programs. What matters is not what the port means in general, but what is supposed to be running on your machine right now. Keep that in mind as you troubleshoot: your job is to find the program that owns this port on your computer, not to find a universal meaning for the number.

Why Your Browser Says It Cannot Reach This Site

When the browser reports that it cannot reach localhost:18789, it is telling you the connection attempt failed at a very early stage. It sent a request to your own machine on port 18789 and got no response at all. That is different from a page loading with an error message written by the server, which would mean the server is running but unhappy about your request. No response at all usually means one of these situations:

First, and most commonly, nothing is listening on that port right now. The program either never started, it crashed, it finished and exited, or it is still starting up. Development servers, in particular, can take a few seconds to be ready, and a background service can fail silently if it hits an error on startup. If you opened the browser tab a moment too early, or after closing the terminal window that was running the server, you will see exactly this error.

Second, the program is running but on a different port. Maybe it defaulted to another port this time, maybe a config file changed, or maybe you misremembered the number. If the program is happily serving on port 18790 or 8080 while you knock on 18789, the result looks identical to nothing running at all. Your browser cannot guess the right door.

Third, something is actively blocking the connection. A firewall rule, a security tool, or a proxy setting can intercept local traffic and refuse it. This is less common for localhost than for internet traffic, because most firewalls trust loopback traffic by default, but it does happen, especially with strict corporate security software or a misconfigured proxy that tries to send even local addresses out to an external server.

Fourth, the browser itself is confused. A cached redirect, a service worker, or a browser extension can interfere. For example, if a previous session redirected localhost:18789 to an HTTPS address, or if the browser is trying to use a proxy for local addresses, you can get a failure even though the server is fine. Trying a different browser, or a private window, is a quick way to rule this out.

The good news is that these four causes have different fingerprints, and you can tell them apart in about a minute once you know where to look. The checklist below does that in order, starting with the fastest checks.

The Five-Minute Checklist That Fixes Most Cases

Work through these in order and stop as soon as something works. Do not jump to reinstalling software or editing system files before you have tried the simple steps, because most localhost failures are simple.

Step one: check whether the program is actually running. Look for its terminal window, its icon in the system tray or menu bar, or its entry in your task manager or activity monitor. If you started it from a terminal and then closed that terminal, the program probably stopped with it. Start it again and watch its output. A healthy server usually prints a line saying it is listening, often with the exact address and port. If you see an error instead, that error message is your real clue — read it before doing anything else.

Step two: confirm the port. Read the program’s startup message or its settings. Does it actually say 18789? If it says a different number, open that number instead. If it says it is listening on all interfaces or on 0.0.0.0, localhost should still work, but note the port it reports. If the startup message is missing entirely, check the program’s documentation or configuration file for its default port setting.

Step three: try 127.0.0.1 instead of localhost. Type http://127.0.0.1:18789 into the address bar. If that works and localhost does not, the problem is name resolution on your machine — localhost is not mapping to 127.0.0.1 the way it should. That is rare, but it is a useful split: it tells you the server is fine and the name lookup is the broken piece. If neither works, the server or the port is the problem, not the name.

Step four: try a different browser or a private window. This rules out cache, extensions, and stale redirects in one move. If the page loads in a private window, clear the original browser’s cache for localhost, disable extensions one at a time, or clear site data for the localhost address. You do not need to clear your entire browsing history for this.

Step five: restart the service cleanly. Stop it completely, wait a few seconds, and start it again. If it was stuck in a half-started state, or if an old copy was still holding the port, a clean restart clears that. If the restart fails with a message about the address already being in use, you have found your next clue, covered in the section below.

If all five steps pass and the page still will not load, move on to the deeper checks. You have already ruled out the most common causes, which makes the deeper work much shorter.

How to Tell Whether Anything Is Listening on Port 18789

Guessing is slow. Checking is fast. Your operating system can tell you exactly which programs are listening on which ports, and this one check often ends the mystery.

On Windows, open a terminal and run a command that lists listening ports, such as netstat with the options that show listening sockets and the process behind each one. Look for a line with local address port 18789 and a state of listening. The process identifier on that line tells you which program owns it, and you can match that identifier in Task Manager. On macOS or Linux, similar tools exist: lsof with the port flag, or ss with the listening flag, will show you the program name and process identifier for the port. You do not need to memorize the exact flags for every system; the idea is the same everywhere — ask the system who, if anyone, is holding port 18789.

If the list shows nothing on 18789, your answer is clear: nothing is listening. Go back to starting the service, and pay attention to its output. If the service claims it started but still does not appear in the list, it may have bound to a different port, failed partway through startup, or exited immediately. Its logs are the next place to look.

If the list shows a program you do not recognize on 18789, that is also an answer. Some other tool claimed the port first, and your intended service could not start because the port was taken. You can either stop the unexpected program or move your service to a different port. If the list shows your expected program on 18789 and the browser still cannot reach it, the problem is between the browser and the service — a firewall rule, a proxy setting, or a browser issue — which narrows your search considerably.

One caution: port-checking commands sometimes need administrator privileges to show process names. If you see the port but not the program name, rerun the command with elevated permissions. And do not be surprised if a port check shows a program listening on an IPv6 address rather than IPv4. Most modern systems handle both, and browsers usually try both, but a service bound only to one address family can behave oddly. If you see that pattern, the service’s configuration — specifically which address it binds to — is worth a look.

What to Do When the Port Is Already in Use

An “address already in use” error is one of the most helpful errors you can get, because it tells you exactly what is wrong: two programs want the same port, and only one can have it. The fix is to decide which one should win.

First, find out what is holding the port, using the listening-port check from the previous section. Often it turns out to be a leftover copy of the very service you are trying to start. You started it once, closed the window, assumed it stopped, but a background copy kept running. In that case the old copy may still be serving your content perfectly well — try opening the page again — or it may be stuck. Stopping the old copy and starting fresh usually clears it.

Sometimes the holder is a different program entirely. A previous project, a media server, a sync tool, or another development server may have claimed 18789 earlier in the day. If you do not need that program right now, stop it and start your intended service. If you need both programs running, change one of their ports. Most services let you set the port in a configuration file, a settings screen, or a command-line option when you start them. Pick a free high port, update any bookmark or link you use to open the service, and move on. There is no rule that says a given program must stay on 18789 forever.

A word about restarting your whole computer as a fix: it works, because it clears every held port, but it is a blunt tool. It also hides the cause. If the same conflict keeps returning, you have a program that auto-starts and grabs the port on boot, and a restart will only buy you time until the next boot. Finding the holder once is better than restarting repeatedly.

Also watch for the case where the service starts, serves for a while, and then stops when you close a terminal window or log out. Some programs are tied to the session that launched them. If that is happening, look for the program’s own guidance on running it as a background service or in a terminal session that persists. The details vary by system, but the principle is the same: a server needs to keep running after you look away, or the browser will find an empty port when you come back.

Firewall, Antivirus, and Browser Problems That Block Localhost

If the service is running and listening on 18789, but the browser still cannot reach it, something between the two is interfering. The most likely suspects are firewall software, security tools, and proxy settings.

Start with the proxy. Many workplaces and some VPN tools route all browser traffic, including local traffic, through a proxy server. A proxy has no business handling localhost traffic, because localhost never leaves your machine, but a misconfigured proxy setting can try anyway and fail. Browsers and operating systems both have a setting for bypassing the proxy for local addresses. Make sure localhost and 127.0.0.1 are on that bypass list. If you are using a VPN, try disconnecting it briefly as a test. If the page loads with the VPN off, the VPN’s routing is the issue, and its settings — or its own bypass list for local addresses — are where the fix lives.

Next, consider firewall and antivirus software. Most firewalls allow loopback traffic by default, and most antivirus tools do not block it at all, but strict security suites sometimes inspect even local connections. You do not need to turn your firewall off permanently to test this — and you should not. Instead, check whether the security tool has a log of blocked connections, or whether it prompts you to allow the program when it first tries to listen. If the program was denied permission to listen on the network the first time it asked, it may be silently blocked now. Allowing the program through the firewall, for private networks at least, usually resolves it. If you are on a work machine with centrally managed security software, this may be a question for your IT team rather than a setting you can change yourself.

Browser problems are easier to test. Extensions that block requests, rewrite addresses, or force HTTPS can all interfere with a plain local address. A private window disables most extensions by default, which is why it is such a useful test. If a private window works, re-enable extensions one at a time in the normal window until the problem returns. Also check whether the browser is forcing HTTPS for localhost. Local development servers usually serve plain HTTP, not HTTPS, and an automatic upgrade to HTTPS will fail because there is no secure server on the other end. Typing the full http:// address explicitly, rather than letting the browser guess, avoids that trap.

One more browser quirk worth knowing: some browsers remember a previous redirect. If you once visited localhost:18789 and the server redirected you elsewhere, the browser may replay that redirect from cache even after the server changed. Clearing site data for localhost, or testing in a private window, exposes this quickly.

How to Change the Port Safely

Changing the port is not a failure. It is a normal part of running local services. Ports collide, defaults get taken, and different projects need different doors. The safe way to change a port has three steps: pick a free port, tell the program, and update your own links.

Pick a port above 1024, because low ports are reserved for system services and often need administrator privileges. High ports in the range developers commonly use — the thousands and tens of thousands — are fine. Avoid picking a port you know another program already uses. You can verify a candidate is free with the same listening-port check: if nothing shows up for that port, it is available.

Tell the program through its own setting, not by editing random files. That setting might be a command-line flag, an environment variable, a configuration file, or a settings screen, depending on the program. After changing it, restart the program and confirm from its startup output that it is now listening on the new port. Then update your bookmark, your project documentation, or the link in whatever tool opens the service for you. The most common “port change didn’t work” story is someone changing the setting but continuing to open the old address out of habit.

Keep a small note for yourself when you change a port away from a default: which program, which new port, and why. Future you, opening the project after a month away, will be grateful. Local development has a way of accumulating these small customizations, and a one-line note saves a repeat of the whole troubleshooting session.

When Localhost:18789 Is Supposed to Be Something Else

There is one more possibility worth mentioning, because it changes the whole approach: maybe nothing on your machine was ever supposed to serve on 18789, and the address came from somewhere else. Perhaps you followed a tutorial or a forum post that used 18789 as an example, or you copied a link from a guide written for a different program. Perhaps a bookmark points to a service you uninstalled months ago. In those cases no amount of troubleshooting on your machine will conjure a server into existence, because there is no server to fix. The right move is to go back to the source of the address and ask what program it belongs to, then install or start that program.

Similarly, if you are following a setup guide and the guide’s program is supposed to pick its own port automatically, the guide may tell you to check the program’s output for the actual address rather than assuming a number. Dynamic ports are common: a program may grab whatever free port the system offers and print it in its startup message. If that is your situation, the number in the guide is illustrative, and the number in the program’s output is the truth.

Finally, a note on safety. Localhost services are private by design: they are reachable only from your own machine. That privacy disappears the moment you expose a local port to your network or the internet, for example through port forwarding or a tunnel, so that someone else can reach it. Do not do that casually, and never do it for a development server that has no authentication, because anyone who can reach it may be able to read or change what it serves. Troubleshooting localhost is safe precisely because it stays local. Keep it that way unless you have a specific reason, and a specific security plan, to open it up.

Frequently Asked Questions

What does localhost:18789 mean?

It means “this computer, port 18789.” Localhost is your own machine, and 18789 is the port number a program on that machine is expected to listen on. The number itself is not a standard web port; it belongs to whatever program chose it as a default or was configured to use it.

Why does my browser say it cannot reach localhost:18789?

Because nothing answered on that port. Usually the service is not running, it is running on a different port, or something is blocking the connection. The browser did its job; there was simply no server on the other end of the request.

Is localhost:18789 a website I can visit from anywhere?

No. Localhost always refers to the computer making the request. Your localhost:18789 and someone else’s localhost:18789 are two different machines. A link to localhost only works on the machine where the service is actually running.

How do I find out what is using port 18789?

Use your system’s port-listing tool: netstat on Windows, or lsof or ss on macOS and Linux, filtered to port 18789. The output shows whether anything is listening and which program owns the port. Administrator privileges may be needed to see program names.

Should I change the port or stop the program using it?

Either works. If you need the other program, change your service’s port in its settings. If you do not need the other program, stop it and keep 18789. The deciding factor is which program you actually want running right now.

Is it safe to open localhost services to the internet?

Not without care. Development servers often have no login and no encryption, and exposing one can let strangers read or modify your data. Keep local services local unless you have a deliberate reason and a security plan for sharing them.

The service was working yesterday. What changed?

The most common changes are a reboot that stopped an auto-start service, a closed terminal that killed the server, a software update that changed a default port, or a newly installed program that claimed the port first. Work through the five-minute checklist; the startup output of the service usually reveals which of these happened.

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