AssertionError Extension Access Disabled Because Of Command Line Flags | Quick Fix Steps

What This Extension Access Assertionerror Means

When the web UI throws the message ‘assertionerror extension access disabled because of command line flags’, it is not a random crash. The code checks the options you pass into Stable Diffusion at launch and shuts down the extensions tab when a safety switch is active for that process. The main idea is straightforward: some flags tell the app that the instance might be shared, so installing new extensions from inside the browser could be risky.

In practice this assertion appears when you open the Extensions panel or press an Install or Update button. The back end sees that extension access is disabled and raises the assertion instead of running the install code. That means the fix does not live inside the Extensions tab itself. You have to change the way you start the web UI so the safety check passes again.

In Stable Diffusion forks based on the popular AUTOMATIC1111 project, the assertion lives inside the extensions helper file. That code reads shared options and checks a field called disable_extension_access. Flags such as --listen, --share, or certain API presets flip that field on during startup. The assertion fires so that someone using a public link cannot silently pull code from an untrusted repository. If you run only on a home computer, you control that risk yourself, which is why many guides show the override flag as a normal part of the launch command.

Fixing AssertionError Extension Access Disabled Because Of Command Line Flags

The error always comes from the same check inside the web UI code. It asks whether the command line options include a flag that disables extension access. If the answer is yes, the check fails and you see ‘extension access disabled because of command line flags’. Once you remove that block or pair it with the correct override flag, the assertion clears and extension installs work again.

You can choose between two broad approaches. You can strip out or change the flags that flip extension access off. Or you can add the special override flag that allows extension access even when the UI listens on the network for other users. Both routes work, but the right one depends on your setup and how locked down you want the server to be.

Locating Command Line Flags In Different Setups

The message about extension access only makes sense when you know where the launch flags live. On a local Windows install they sit in a batch file. On Linux or macOS they sit in a shell script. In Docker or Unraid they sit inside a compose file or template, and on hosted services or Colab they often hide in a launch cell that you do not touch very often.

Use the table below as a quick map so you know where to look before you change anything.

Setup	Where Flags Live	What To Edit
Windows local install	webui-user.bat in the web UI folder	Line that starts the launch script with extra flags
Linux or macOS	webui-user.sh or your custom start script	Command that runs python launch.py with flags
Docker or Unraid	Compose file or container template	Field that adds extra launch arguments
Colab or hosted notebook	Setup cell that calls the launch script	Line with launch arguments, if the notebook allows edits

Once you know which file holds the launch options, you can scan for flags that interfere with extensions. The most common ones are network and sharing flags plus any direct block flag. In many installs, the extension code treats any shared public URL as unsafe by default unless you add a matching override.

Step By Step Fixes For Common Setups

Before you change flags, take a moment to decide how open you want the server to be. If the web UI only runs on your own machine, enabling extension access with an override flag is usually fine. If you share the UI on a public link or host it for friends, you want to limit who can install code and you may prefer to toggle flags only while you add extensions.

• Check for a direct disable flag — Open your launch script and search for any option that looks like --disable-extension-access or a very similar variant. If you see it, remove it from the command, save the file, restart the web UI, and test the Extensions tab again.
• Look for network sharing flags — Flags such as --listen, --share, or some API modes often flip extension access off for safety. The UI assumes that a shared instance should not pull random code from the internet without an explicit override.
• Add the insecure extension override when needed — If you want to keep a flag such as --listen but still manage extensions, add --enable-insecure-extension-access on the same command line. Restart the web UI and try installing or updating an extension from the index.
• Temporarily remove sharing flags — A simple low risk pattern is to stop the script or container, remove the network sharing flags, restart locally, install or update all extensions you want, then shut down and start again with your original flags once you are done.
• Watch the terminal when you test — Keep an eye on the console window while you press Install or Update. If the assertion still fires, there is at least one remaining flag or extra setting that keeps extension access disabled.

Each of these steps keeps attention on the real source of the error, which is the launch command. Once you match the flags to your needs, the browser side controls usually start to work again without extra tuning.

Colab And Hosted Notebook Gotchas

Many people meet this error inside a Colab notebook or cloud notebook that wraps Stable Diffusion. In that case the author of the notebook might have hard coded safe flags, including those that disable extension access. The goal is to stop users from installing unreviewed code onto a shared machine or through a public share link.

When the flags come from someone else’s notebook, your options are a bit tighter. The list below sums up the most common patterns.

• Check for a visible launch cell — Some notebooks show a cell with the full launch command. If the cell is editable, you can add --enable-insecure-extension-access or remove a block flag, then run the cell again before you launch the UI.
• Look for helper scripts — Other notebooks download a helper script and run it with fixed flags. You may be able to click through to the script on the repository page, create your own copy with safer defaults, and change the URL in the setup cell.
• Use a different notebook when flags are locked — If there is no way to change the launch command, the only realistic path is to switch to a notebook that allows extension access or provides a separate extension friendly build.

Cloud and Colab setups are handy when you have limited hardware, but the trade off is less control over command line options. If extension access matters to your workflow, picking a notebook that exposes the launch flags will save time and frustration.

Staying Safe While Enabling Extension Access

Extension access is powerful because every extension is just Python code that runs inside the same process as your main web UI. When you flip on --enable-insecure-extension-access in a shared instance, any user with access to the browser can install code that runs on the host machine. That is why the assertion about extension access exists in the first place.

You can lower the risk without giving up the features that matter most to you.

• Limit who can reach the UI — Prefer binding the server to 127.0.0.1 on a home machine and reaching it through a browser on the same device. If you must share across the network, keep the audience small and trusted.
• Audit installed extensions often — From time to time, open the Extensions tab and remove entries you no longer use. Fewer active extensions mean fewer moving parts when you diagnose odd errors later.
• Pin to known sources — When you install extensions by URL, prefer official repositories or long running projects with a visible history. Random one off forks with no readme or activity log carry more risk.
• Keep a backup of your config and models — Copy your config files, models, and embeddings to a safe folder or separate drive. If an extension breaks the UI, you can wipe the app folder and reinstall without losing your heavy downloads.

This approach keeps the intent of the original safety check while still giving you control over the extension system. The assertion disappears, but your setup still respects basic good sense around who can add code and where it comes from.

When The Error Still Appears After Changing Flags

Sometimes the ‘assertionerror extension access disabled because of command line flags’ message keeps showing up even after you think the launch options look clean. That usually means there is a second layer that passes flags into the app, or a cached configuration that overrides your changes. Walking through a few extra checks often flushes out the hidden source.

• Confirm which script actually runs — If you have several copies of the web UI on disk, make sure your shortcut or service points to the right folder. It is easy to edit one launch file while another copy still runs with the old flags.
• Search for flags in container settings — In Docker tools such as Unraid there may be a field that adds extra launch arguments. Open the container template, scan for network and disable flags, and clear them before the next start.
• Check for wrapper apps or helpers — Some one click installers wrap the real launch script. Open their config window or text files and search for the same flags so you do not miss a hidden layer.
• Review logs after a clean restart — Shut everything down, start the app from a terminal, then try the Extensions tab once more. Scroll through the log to see which flags the app says it is using at runtime.

By the time you have walked through the extra checks, the assertion is usually gone and extension updates behave like any other part of the UI again. The main lesson is that this error is not random. It is the app telling you that a specific launch option is still in force. Once you clear that option, the extensions tools work just as expected.